Tuna Tuna - health

Tuna Tuna

While the consumption of canned tuna accounts for more Americans eating tuna than any other type of fish, it doesn't compare to the wonderfully firm, dense and meaty flavor and texture of fresh tuna. Both canned and fresh tuna are available throughout the year. December is the time to get fresh Hawaiian tuna.

Tuna is found in the warm water areas of the Pacific, Atlantic and Indian Oceans as well as the Mediterranean Sea. People have been enjoying tuna as a food ever since time immemorial. And while fresh tuna has been enjoyed by coastal populations throughout history, smoked and pickled tuna was widely consumed since ancient times.

Food Chart
This chart graphically details the %DV that a serving of Tuna provides for each of the nutrients of which it is a good, very good, or excellent source according to our Food Rating System. Additional information about the amount of these nutrients provided by Tuna can be found in the Food Rating System Chart. A link that takes you to the In-Depth Nutritional Profile for Tuna, featuring information over 80 nutrients, can be found under the Food Rating System Chart.

Health Benefits
Description
History
How to Select and Store
How to Enjoy
Individual Concerns
Nutritional Profile
References

Health Benefits

Tuna fish are truly a nutrient-dense food. An excellent source of high quality protein, tuna are rich in a variety of important nutrients including the minerals selenium, magnesium, and potassium; the B vitamins niacin, B1 and B6; and perhaps most important, the beneficial omega-3 essential fatty acids. Essential fatty acids are so named because they are essential for our health but cannot be made by the body; they must therefore be obtained from foods. Cold-water fish like tuna are a rich source of the omega-3 essential fats, a form of essential fatty acids in which the standard American diet is sorely deficient. (The other form of essential fatty acids, the omega-6s, are plentiful in a variety of commonly consumed oils such as corn and safflower oil. In fact, the omega-6s are so plentiful in the typical American diet that too much omega-6 is consumed in proportion to omega-3s--an imbalance that promotes inflammation, thus contributing to virtually every chronic disease in which inflammation is a key component.)

Enjoying Tuna or Salmon Just Twice Weekly May Help Raise Omega-3 Levels at Least as Effectively as Daily Fish Oil Supplementation

A small group of healthy women, all pre-menopausal in age, consumed a daily average of 485 mg of EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), either by eating salmon and/or albacore tuna, fish rich in omega-3 fats, twice a week or by taking 1-2 capsules of fish oil daily.

After 16 weeks, levels of omega-3s in their red blood cells were measured. In those eating fish, EPA+DHA levels increased from an average of 4.0 to 6.2 of total fatty acids. In those taking capsules, EPA+DHA levels rose a virtually identical amount, from 4.3 to 6.2% of total fatty acids. EPA in red blood cells increased significantly more rapidly in the fish group than in the capsule group during the first 4 weeks, but rates did not differ significantly between groups thereafter.(Harris WS, Pottala JV, et al., Am J Clin Nutr.)

Wouldn't you rather enjoy a delicious meal that includes a serving of omega-3-rich fish twice a week than swallow a capsule of fish oil every day, especially as gastrointestinal upset, burping and a fishy aftertaste are common side effects of taking fish oil capsules? For links to our quick, easy and palate-pleasing omega-3-rich recipes, click Recipe Assistant and select omega-3s from the list of "nutrients to require."

Cardiovascular Health

Omega-3 fatty acids provide a broad array of cardiovascular benefits. Omega-3s benefit the cardiovascular system by helping to prevent erratic heart rhythms, making blood less likely to clot inside arteries (which is the ultimate cause of most heart attacks), and improving the ratio of good (HDL) cholesterol to potentially harmful (LDL) cholesterol. And, as mentioned above, omega-3s reduce inflammation, which is a key component in the processes that turn cholesterol into artery-clogging plaques. In a recent population-based prospective study, modest consumption of tuna was actually found to be associated with lower risk of death from ischemic heart disease in individuals 65 years and older.

Tuna is also a very good source of vitamin B6, which, along with folic acid, lowers levels of homocysteine. Homocysteine, an intermediate compound produced during the methylation cycle, is directly damaging to artery walls, and elevated blood levels of homocysteine are considered an important risk factor for atherosclerosis.

Increases Heart Rate Variability—A Measure of Heart Muscle Function

Yet another way in which consuming fish rich in omega-3 fats, such as tuna, promotes cardiovascular health is by increasing heart rate variability (HRV), a measure of cardiac function, in as little as three weeks, according to a study published in the April 2005 issue of Chest.

By providing greater variability between beats, the marine omega 3 fatty acids, EPA and DHA, reduce the risk of arrhythmia and/or sudden death.

Researchers from Atlanta, GA, Boston, MA, and Cuernavaca, Mexico, took the HRV of 58 elderly patients every other day for two months to establish an HRV baseline for each participant. For the next 11 weeks, half of the study participants took a daily 2 gram supplement of fish oil and the other half took a daily 2 gram supplement of soy oil.

Patients in both groups experienced a significant increase in HRV, with those who took fish oil achieving a greater increase in a shorter time period. Patients who received fish oil experienced increased HRV within the first 2.7 weeks, whereas it took 8.1 weeks for a significant increase in HRV to be seen in the group taking soy oil.

On the other hand, while none of the study participants experienced significant negative side effects, 41% of participants in the fish oil group reported belching, compared to 16% in the soy oil group.

"Our findings contradict the current belief in the medical community that increasing the intake of omega-3 fatty acids produces only long-term cardiac benefits," said the study's lead author, Fernando Holguin, MD, Emory University School of Medicine, Atlanta, GA. "In fact, our study group showed improvements in heart function in as little as two weeks." "Studies like this demonstrate that there are additional approaches we can take to protect ourselves from heart attacks," said Paul A. Kvale, MD, FCCP, President of the American College of Chest Physicians. "It's exciting to see the potential for omega-3 fatty acids in improving heart function when it complements a healthy lifestyle of exercising, maintaining a healthy weight, and getting eight hours of sleep." We'd add eating healthful foods to this proactive list. Rather than pop a daily pill, we'd rather enjoy a daily "dose" of delicious tuna, salmon or soyfoods. For recipes certain to not only increase your heart rate variability but also your delight in eating, click Recipes.

Protection against Fatal Heart Arrhythmia

A healthy way of eating that includes at least 10 ounces of omega-3-rich fish each week improves the electrical properties of heart cells, protecting against fatal abnormal heart rhythms, suggests a study from Greece.

"Long-term consumption of fish is associated with lower QT interval in free-eating people without any evidence of cardiovascular disease. Thus, fish intake seems to provide anti-arrhythmic protection at a population level," wrote the authors in the American Journal of Clinical Nutrition. (Chrysohoou C, et al.)

The QT interval is a measure of the heart's electrical cycle, from the beginning of ventricular depolarization, the Q wave, to the end of the T wave, at which point cardiac repolarization is complete.

A lower QT score indicates a lower resting heart rate. As a higher resting heart rate has been linked to an increased risk of sudden death, the result of approximately 50% of heart attacks, lowering the resting heart rate provides significant health benefit.

Researchers at the University of Athens enrolled 3,042 people (1,514 men, aged 18-87, and 1,528 women, aged 18-89), who used a validated food frequency questionnaire to record their food intake of 156 different foods. Along with alcohol consumption and physical activity were also recorded, and electrocardiography was used to measure several indexes of study participants' heart rate.

After the raw data scan, those who ate more than 10 ounces (300 grams) of fish per week were found to have QT scores 13.6% lower than people who did not eat fish.

After adjusting the results for potentially confounding factors such as age, sex, physical activity status, BMI, smoking habits and intake of nuts, the reduction in QT scores in those eating 10 or more ounces of fish each week rose to 29.2%, compared to those who did not eat fish.

In an earlier study, Harvard researchers reported that among those consuming the most fish, heart rate was 2.3 beats per minute lower and likelihood of prolonged QT was 46% lower. Similar results were found in study participants taking 1 gram of omega-3s daily. The mechanism behind these benefits is thought to be omega-3 fats' effects on the flow of sodium and calcium in the ion channels, which are involved with electrical signaling in cells.

Practical Tip: A typical serving of fish is 4 ounces, so just 3 servings of omega-3-rich fish, such as tuna, each week would provide 2 ounces more than the 10 ounces this research indicates confers significant protection against sudden death from a heart attack. For great, quick and easy recipe ideas, take a look at our Recipe Assistant.

Just Two Servings of Omega-3-rich Fish a Week Can Lower Triglycerides

Triglycerides are a form in which fat is carried in your bloodstream. In normal amounts, triglycerides are important for good health because they serve as a major source of energy. High levels of triglycerides, however, are associated with high total cholesterol, high LDL (bad) cholesterol and low HDL (good) cholesterol), and therefore, with an increased risk of cardiovascular disease.

In addition, high triglycerides are often found along with a group of other disease risk factors that has been labeled metabolic syndrome, a condition known to increase risk of not only heart disease, but diabetes and stroke. (Metabolic syndrome is the combined presence of high triglycerides, increased blood pressure, high blood sugar, excess weight, and low HDL (good) cholesterol.)
Triglyceride Levels
Less than 150 mg/dL Normal
150-199 mg/dL Borderline-high
200-499 mg/dL High
500 mg/dL Very High

*Note: Triglycerides are most accurately measured after an 8-12 hour fast.

In this 6-month study involving 142 overweight men and women with high triglycerides, subjects were divided into 5 groups, one of which served as a control group, 2 of which ate 2 servings of fish high in omega-3s while also replacing their normal household fats with fat high in sunflower (Group 1) or canola oil made from rapeseed (Group 2), and 2 of which ate 2 weekly servings of white fish while also replacing their normal household fats with ones high in sunflower (Group 3) or canola oil made from rapeseed (Group 4).

Canola oil also provides some omega-3 fats, with an omega-6:omega-3 ratio of 2:1, while sunflower oil contains omega-6, but no omega-3 fats.

At the end of the study, triglyceride levels had dropped 6.6% in the omega-3-rich fish groups combined. Triglycerides dropped mostâ€"10.4%â€"in those consuming omega-3-rich fish and canola oil. In those eating omega-3-rich fish and sunflower oil, triglycerides dropped 2.8%. Bottomline: A healthy way of eating that incorporates at least 2 weekly servings of fish and other food sources of omega-3 fats, such as flaxseed or canola oil, may significantly lower triglyceride levels. Replacing normal household fats with flaxseed oil, in which the ratio of omega-6:omega:3 fats is 1:4, might result in an even larger drop in triglyceride levels.

Help Prevent and Control High Blood Pressure

Individuals whose diets provide greater amounts of omega-3 fatty polyunsaturated fatty acidsâ€"and tuna is a good source of these essential fatsâ€"have lower blood pressure than those who consume less, shows data gathered in the International Study of Macro- and Micro-nutrients and Blood Pressure (INTERMAP) study (Ueshima H, Stamler J, et al. Hypertension).

The INTERMAP is a study of lifestyle factors, including diet, and their effect on blood pressure in 4,680 men and women aged 40 to 59 living in Japan, China, the U.S. and the U.K. Blood pressure was measured and dietary recall questionnaires were completed by participants on four occasions. Dietary data was analyzed for levels of omega-3 fatty acids from food sources including fish, nuts, seeds and vegetable oils.

Average daily intake of omega-3 fatty acids was 2 grams. Participants with a high (o.67% kcal) omega-3 fatty acid percentage of their daily calorie intake had an average systolic and diastolic blood pressure reading that was 0.55/0.57 mm Hg less, respectively, than participants with lower intake. Previous research has found that a decrease of 2 mm Hg reduces the population-wide average stroke mortality rate by 6 percent and that of coronary heart disease by 4%.

Higher omega-3 fatty acid intake among the 2,238 subjects who were not using drugs, supplements, or a special diet for hypertension, heart disease, or diabetes was associated with a 1.01/0.98 mm Hg reduction in systolic and diastolic blood pressure, respectively.

For the 2,038 subjects in this group who did not have hypertension, greater intake was associated with a 0.91/0.92 mm Hg average systolic and diastolic reduction.

Lead author Hirotsugu Ueshima, MD of Shiga University of Medical Science in Japan, noted that the beneficial effect of omega-3 fats was even greater in people who had not yet developed high blood pressure.

The researchers also found that omega-3s from nuts, seeds, and vegetable oilsâ€"such as walnuts and flaxseedâ€"had just as much impact on blood pressure as omega-3s from fish.

"With blood pressure, every millimeter counts. The effect of each nutrient is apparently small but independent, so together they can add up to a substantial impact on blood pressure. If you can reduce blood pressure a few millimeters from eating less salt, losing a few pounds, avoiding heavy drinking, eating more vegetables, whole grains and fruits (for their fiber, minerals, vegetable protein and other nutrients) and getting more omega-3 fatty acids, then you've made a big difference," said Ueshima.

Stroke Prevention

A recent study showed that eating fish lowers the risk of certain types of strokes. The study, which involved almost 80,000 nurses during a 15-year period revealed that those women who ate fish 2 to 4 times per week had a 27% reduced risk of stroke compared to women who ate fish one a month. Eating fish five or more times per week reduced the risk of certain strokes 52%.

A meta-analysis of eight studies published in the July 2004 issue of Stroke provides further support that eating fish is protective against stroke in men as well as women. Eating fish, such as tuna, as little as 1 to 3 times per month may protect against ischemic stroke (a stroke caused by lack of blood supply to the brain, for example, as a result of a blood clot).

Data on nine independent groups participating in eight different studies found that, compared to those who never consumed fish or ate fish less than once per month, risk of ischemic stroke dropped:

9% in those eating fish 1 to 3 times per month
13% in those eating fish once per week
18% in those eating fish 2 to 4 times per week
31% in those eating fish 5 or more times each week

Protection Against Atrial Fibrillation (Heart Arrhythmia)

Eating tuna that's broiled or baked, but not fried, may reduce risk of atrial fibrillation, the most common type of heart arrhythmia, especially in the elderly, according to a Harvard study published in the July 2004 issue of Circulation. In the 12-year study of 4,815 people 65 years of age or older, eating canned tuna or other broiled or baked fish 1 to 4 times a week correlated with increased blood levels of omega-3 fatty acids and a 28% lower risk of atrial fibrillation. Eating broiled or baked fish 5 times a week lowered risk even moreâ€"a drop in atrial fibrillation risk of 31%. Eating fried fish, however, provided no similar protection. Not only is fried fish typically made from lean fish like cod and Pollack that provide fewer omega-3 fatty acids, but in addition, frying results in the production of damaged, free-radical-laden fats in the fish as well as the frying oil.

In further research to determine if the omega-3 fats found in fish oil were responsible for fish's beneficial effects on the heart's electrical circuitry, Dariush Mozaffarian and colleagues from Harvard Medical School analyzed data on fish intake and electrocardiogram results from 5096 adults, aged 65 or older, who were enrolled in the Cardiovascular Health Study from 1989-1990.

Eating tuna or other broiled or baked fish at least once a week was associated with lower heart rate (-3.2 beats/minute) and a 50% lower likelihood of prolonged ventricular repolarisation (the period of time it takes the heart to recharge after it beats, so it can beat again), compared to those consuming fish less than once a month.

Consuming 1 gram/day of omega-3 fatty acids from fish was associated with 2.3 beats/minutes lower heart rate and a 46% lower risk of prolonged ventricular repolarisation.

Eating fish at least 5 times per week was associated with an even healthier heart rhythm. However, eating fried fish (typically sold in the U.S. as fish burgers or fish sticks) was not associated with increased blood levels of omega 3 fats or any beneficial electrocardiogram results. In fact, a previous study led by the same researcher (Mozaffarian, Am J Cardiol 2006 Jan) found that while eating baked or broiled fish was linked to a slower but more powerful heart beat and lower blood pressure, eating fried fish was associated with heart muscle motion abnormalities, a reduced ejection fraction, lower cardiac output, and higher blood pressure. Since irregular heart beats are a major precipitating factor in sudden death due to cardiac arrest, promoting a healthy heart rhythm by eating baked or broiledâ€"not friedâ€"fish several times a week makes very good sense. Happily, as our recipes, such as 15 Minute Asian Tuna show, it's a quick, easy and most importantly, delicious prescription.

Eating Fish Daily Provides Substantially More Protection against Heart Attack

While as little as a weekly serving of fish lowers risk of ischemic stroke, enjoying a daily serving omega-3-rich fish, such as tuna, provides significantly greater reduction in the risk of coronary heart disease than eating fish even as frequently as a couple of times a week, show the findings of a study published in the January 17, 2006 issue of Circulation, the journal of the American Heart Association.

Researchers in Japan followed 41,578 men and women aged 40 to 59, none of whom had cardiovascular disease or cancer when the study began, from 1990-1992 to 2001. Food frequency questionnaires completed at the beginning of the study and in 1995, provided information on weekly fish intake, which was analyzed for omega-3 content.

When individuals whose fish consumption was in the top one-fifth of participants at 8 times per week were compared to those whose intake was in the lowest fifth at once per week, they were found to have a 37% lower risk of developing coronary heart disease and a 56% percent lower risk of heart attack.

When the effect of omega-3 fatty acid intake on cardiovascular risk was analyzed, coronary heart disease risk was lowered by 42% among those whose intake was the highest at 2.1 grams per day or more compared to those whose intake was the lowest at 300 milligrams per day. Those whose intake of omega 3s was in the top fifth received a 65% reduction in the risk of heart attack compared to those whose omega 3 intake was lowest.

The authors theorize that daily fish consumption is highly protective largely due to the resulting daily supply of omega-3 fatty acids, which not only reduce platelet aggregation, but also decrease the production of pro-inflammatory compounds called leukotrienes. Lowering leukotrienes reduces damage to the endothelium (the lining of the blood vessels), a key factor in the development of atherosclerosis.

"Our results suggest that a high fish intake may add a further beneficial effect for the prevention of coronary heart disease among middle-aged persons," note the study's authors.

Fish, Fruit and Vegetables Protective against Deep Vein Thrombosis, Pulmonary Embolism

Deep vein thrombosis is a dangerous condition in which blood clots develop in the deep veins of the legs, thighs or pelvis, causing swelling and pain. An embolism is created if a part or all of the blood clot in the deep vein breaks off from the site where it was created and moves through the venous system. If the clot lodges in the lung, a very serious condition, pulmonary embolism, arises.

Fortunately, a healthy way of eating offers significant protection, as demonstrated by a prospective study over 12 years that involved almost 15,000 middle-aged adults. While those eating the most red and processed meat doubled their risk of deep vein thrombosis (DVT), those in the upper 3 quintiles of fruit and vegetable intake had a 41-53% lower risk of DVT. And those eating fish, such as tuna, at least once each week were found to have a 30-45% lower DVT risk. (Steffen LM, Folsom AR, et al.,Circulation)

Practical Tip: For protection against deep vein thrombosis, increase your consumption of fruit and vegetables; eat fish at least once a week; and decrease consumption of red and processed meats.

Special Cardiovascular Protection for Postmenopausal Women with Diabetes

Eating omega-3 rich fish, such as tuna, at least twice each week significantly reduces the progression of atherosclerosis in postmenopausal women with diabetes, suggests a Tufts University study published in the September 2004 issue of the American Journal of Clinical Nutrition.

The three year study included 229 women with atherosclerosis, 42% of whom also had diabetes. Although new atherosclerotic lesions were seen in all the women, regardless of fish intake, those who consumed 2 or more servings of fish per week had significantly fewer lesionsâ€"especially if at least one serving was chosen from those high in omega-3 fatty acids, such as tuna, salmon, mackerel or sardines.

Women with diabetes eating less than 2 servings of fish experienced an average 4.54% increase in stenosis (thickening and restriction) in their arteries, compared to an average increase of only 0.06% in women eating 2 servings of any fish per week.

In diabetic women eating less than 1 serving of omega-3-rich fish per week, stenosis increased 5.12% compared to a 0.35% increase in those who ate 1 or more servings of omega-3-rich fish each week.

Eating fish rich in omega-3s is so beneficial because these fats:

lower the amount of lipids (fats such as cholesterol and triglycerides) circulating in the bloodstream
decrease platelet aggregation, preventing excessive blood clotting
inhibit thickening of the arteries by decreasing endothelial cells' production of a platelet-derived growth factor (the lining of the arteries is composed of endothelial cells)
increase the activity of another chemical derived from endothelial cells (endothelium-derived nitric oxide), which causes arteries to relax and dilate
reduce the production of messenger chemicals called cytokines, which are involved in the inflammatory response associated with atherosclerosis

Omega 3s Help Prevent Obesity and Improve Insulin Response

Salmon is particularly beneficial not just for women with type 2 diabetes, but for men with this condition as well, due to its high content of omega 3 fats.

Research presented December 2004 at the 6th Congress of the International Society for the Study of Fatty Acids and Lipids suggests that while saturated fats appear to promote weight gain, the omega 3 fats found in cold water fish, such as tuna, reduce the risk of becoming obese and improve the body's ability to respond to insulin.

The reason why? The omega 3 fatty acid, eicosapentaenoic acid (EPA) stimulates the secretion of leptin, a hormone that helps regulate food intake, body weight and metabolism, and is expressed primarily by adipocytes (fat cells).

EPA, an Omega-3 Fat found in Tuna, Reduces Inflammation

A recently identified lipid (fat) product our bodies make from EPA, called resolvins, helps explain how fish oils provide their anti-inflammatory effects on our joints and improve blood flow.

Resolvins, which have been shown to reduce inflammation in animal studies, are made from EPA by our cellular enzymes, and work by inhibiting the production and regulating the migration of inflammatory cells and chemicals to sites of inflammation.

Unlike anti-inflammatory drugs, such as aspirin, ibuprofen and the COX-2 inhibitors, the resolvins our bodies produce from EPA do not have negative side effects on our gastrointestinal or cardiovascular systems.

Fish and Whole Grains Highly Protective against Childhood Asthma

According to the American Lung Association, almost 20 million Americans suffer from asthma, which is reported to be responsible for over 14 million lost school days in children, and an annual economic cost of more than $16.1 billion.

Increasing consumption of whole grains and fish could reduce the risk of childhood asthma by about 50%, suggests the International Study on Allergy and Asthma in Childhood (Tabak C, Wijga AH, Thorax).

The researchers, from the Dutch National Institute of Public Health and the Environment, Utrecht University, University Medical Center Groningen, used food frequency questionnaires completed by the parents of 598 Dutch children aged 8-13 years. They assessed the children's consumption of a range of foods including fish, fruits, vegetables, dairy and whole grain products. Data on asthma and wheezing were also assessed using medical tests as well as questionnaires.

While no association between asthma and intake of fruits, vegetables, and dairy products was found (a result at odds with other studies that have supported a link between antioxidant intake, particularly vitamins C and E, and asthma), the children's intake of both whole grains and fish was significantly linked to incidence of wheezing and current asthma.

In children with a low intake of fish and whole grains, the prevalence of wheezing was almost 20%, but was only 4.2% in children with a high intake of both foods. Low intake of fish and whole grains also correlated with a much higher incidence of current asthma (16.7%). compared to only a 2.8% incidence of current asthma among children with a high intake of both foods.

After adjusting results for possible confounding factors, such as the educational level of the mother, and total energy intake, high intakes of whole grains and fish were found to be associated with a 54 and 66% reduction in the probability of being asthmatic, respectively.

The probability of having asthma with bronchial hyperresponsiveness (BHR), defined as having an increased sensitivity to factors that cause narrowing of the airways, was reduced by 72 and 88% when children had a high-intake of whole grains and fish, respectively.

Lead researcher, CoraTabak commented, "The rise in the prevalence of asthma in western societies may be related to changed dietary habits." We agree. The Standard American Diet is sorely deficient in the numerous anti-inflammatory compounds found in fish and whole grains, notably, the omega-3 fats supplied by cold water fish and the magnesium and vitamin E provided by whole grains. One caution: wheat may need to be avoided as it is a common food allergen associated with asthma.

Protection against Sunburn

Another benefit of omega-3s anti-inflammatory effects may be their ability to protect our skin against sunburn, and possibly, skin cancer.

Although our increased susceptibility to skin cancer is usually blamed on damage to the ozone layer, dietary changes over the last 75 years, which have resulted in excessive consumption of omega-6 fatty acids and insufficient consumption of omega-3 fats, may also be causing human skin to be more vulnerable to damage from sunlight.

Research by Dr Lesley Rhodes, Director of the Photobiology Unit at the University of Manchester, UK, suggests that eating more omega-3-rich fish, such as tuna, could lessen the inflammation induced by UV-B radiation and help prevent not only the damaging effects of sunburn, but possibly skin cancer as well.

In a paper published in January 2005 in the Journal of Investigative Dermatology, Rhodes explored the ability of omega-3s to protect epidermal and dermal skin cells against UV-B-induced triggering of tumor necrosis factor-alpha, a molecule that induces the production of the pro-inflammatory cytokine, IL-8. Both EPA and DHA significantly suppressed TNF-induced IL-8 secretionâ€"by 54% in the case of EPA and 42% by DHA.

In an earlier one of Dr Rhodes studies, published in the May 2003 issue of Carcinogenesis, 42 healthy volunteers were given a measured dose of ultraviolet light, then divided into two groups. One group was given a daily 4 gram omega-3 fish oil supplement, while the other group received olive oil. After three months, when their responses to ultraviolet light were again measured, the skin cells of volunteers receiving fish oil experienced significantly less DNA damage, leading Rhodes to suggest that increasing consumption of omega-3-rich fish might reduce skin cancer in humans.

Grumpy Teenagers? Tuna May Help Reduce Hostility and Protect Hearts

Feeling really grumpy? Eating more cold water fish such as salmon, tuna, or sardines may help. A study published in the January 2004 issue of the European Journal of Clinical Nutrition found a statistically significant relationship between consuming fish rich in omega-3 fats and a lower hostility score in 3581 young urban white and black adults. Those with the highest intake of omega 3 fats had only a 10% likelihood of being among those with the highest hostility scores. Eating any fish rich in omega 3 fats compared to eating no omega-3-rich fish was also found to drop subjects' chances of being hostile by 12%.

One reason this finding is important: hostility has been shown to predict the development of heart disease, and the young adults in this study were already also enrolled in the CARDIA (Coronary Artery Risk Development in Young Adults) studyâ€"a study that is examining how heart disease develops in adults.

Promote Detoxification

In addition to tuna's omega-3s, the selenium it contains is a necessary component in one of the body's most important antioxidants--glutathione peroxidase--which is critical for a healthy liver, the organ responsible for detoxifying and clearing potentially harmful compounds such as pesticides, drugs, and heavy metals from the body. Selenium also helps prevent cancer and heart disease.

Cancer Protection

Eating even small amounts of fish may protect against ovarian and digestive tract cancers. A total of 10,149 cancer patients with 19 different types of cancer and 7,990 controls were included in a recent study conducted in Spanish hospitals. The researchers determined that eating more fish correlates with a reduced risk of certain cancers. Fish eaters had less cancer in the ovaries, pancreas, and all parts of the digestive tract including the mouth, pharynx, esophagus, stomach, colon and rectum.

Eating fish rich in omega-3 fatty acids, such as tuna, may also help protect against breast cancer, suggest animal and lab culture studies published in the November 2005 issue of the International Journal of Cancer.

In the animal experiments, mice were fed diets rich in either omega-3 (fish oil) or omega-6 (corn oil) fatty acids after which breast cancer cells were implanted. Three weeks later, tumor volume and weight was significantly lower in mice on the omega-3 rich diet.

In the lab culture experiments, when cells were treated with DHA or EPA, sphingomyelinase activity increased by 30-40%, and breast cancer cell growth dropped 20-25%.

Why? Dietary fatty acids are incorporated into cell membranes, and the type of fatty acids dictates how a cell responds and grows. Researchers found that omega-3 fatty acids affect cell growth by activating an enzyme called sphingomyelinase, which then generates the release of ceramide, a compound that induces the expression of the human tumor suppressor gene p21, which ultimately causes cancer cell death.

Lower Your Risk of Leukemia, Multiple Myeloma, and Non-Hodgkins Lymphoma

Fishermen have, in epidemiological studies, been identified as having a lower risk of leukemia, multiple myeloma and non-Hodgkin lymphoma, an occupational benefit that researchers thought might be due to the fact that they eat more fish. Now, a Canadian study published in the April 2004 issue of Cancer Epidemiology Biomarkers & Prevention suggests that persons whose diet includes more weekly servings of fresh fatty fish have a much lower risk of these three types of cancer. Data drawn from a survey of the fish eating habits of 6,800 Canadians indicates that those consuming the most fatty fish decreased their risk of leukemia by 28%, their risk of multiple myeloma by 36%, and their risk of non-Hodgkin lymphoma by 29%. Overall, frequent eaters of fatty fish reduced their risk for all forms of lymphomas by 30%.

Some of the cancer protective effects of fish, such as tuna, may come from its being a great source of omega 3 fatty acids, which have themselves shown impressive anticancer effects, especially important in protection against breast cancer. Recent in vitro (test tube) evidence suggests that this beneficial effect is related to the fact that when omega-3s are consumed in the diet, they are incorporated into cell membranes where they promote cancer cell apoptosis via several mechanisms including: inhibiting a pro-inflammatory enzyme called cyclooxygenase 2 (COX 2), which promotes breast cancer; activating a type of receptor in cell membranes called peroxisome proliferator-activated receptor (PPAR)-α, which can shut down proliferative activity in a variety of cells including breast cells; and, increasing the expression of BRCA1 and BRCA2, tumor suppressor genes that, when functioning normally, help repair damage to DNA, thus helping to prevent cancer development.

Tuna and Other Fatty Fish Highly Protective against Kidney Cancer

Consumption of fatty fish, such as tuna, offers significant protection against renal cell carcinoma, the most common form of kidney cancer, suggests evidence presented in a 15.3-year epidemiological study involving 61,433 women who participated in the Swedish Mammography Cohort Study (Wolk A, Larsson SC, JAMA).

Renal cell carcinoma (RCC), the 10th most common form of cancer with a male:female ratio of 5:3, accounts for more than 80% per cent of all kidney cancers. Although an earlier review of prospective cohort studies (MacLean et al, JAMA) did not support the hypothesis that fish consumption is protective, the authors of the new JAMA study point out that virtually all the other studies on the subject, including MacLean's, did not take into account whether the fish consumed were fatty or lean fish.(Fatty fish contain 20 to 30 times more omega-3 (DHA and EPA) than lean fish, which provide 3-5 times more vitamin D.)

When this distinction was considered, the researchers found that those who consumed one or more serving of fatty fish each week had a 44% decreased risk of RCC compared with those who consumed no fatty fish.

Plus, those who reported long-term consumption between the beginning of the study and the 10-year follow-up had a dramatic 74% lower risk.

In contrast, no association was found between consumption of lean fish or other seafood and incidence of RCC.

Wolk notes,"Our results support the hypothesis that frequent consumption of fatty fish may lower the risk of RCC, possibly due to increased intake of fish oil rich in EPA and DHA, as well as vitamin D."

Fatty Fish Also Protective against Colon Cancer

A diet rich in the omega-3 fats found in cold water fish, such as tuna, greatly reduces risk of colorectal cancer, indicates a study comparing 1,455 subjects with colorectal cancer to 1,455 matched healthy controls.

Those whose diets provided the most omega-3s had a 37% reduction in colorectal cancer risk, compared to those whose diets provided the least. Colorectal cancer risk was 41% lower in those with the highest average intake of EPA, and 37% lower in those whose diets supplied the most DHA. (Theodoratou E, McNeill G, et al. Am J Epidemiol.)

A diet rich in the omega-3 fats found in cold water fish greatly reduces risk of colorectal cancer, indicates a study comparing 1,455 subjects with colorectal cancer to 1,455 matched healthy controls.

Those whose diets provided the most omega-3s had a 37% reduction in colorectal cancer risk, compared to those whose diets provided the least. Colorectal cancer risk was 41% lower in those with the highest average intake of EPA, and 37% lower in those whose diets supplied the most DHA.

Reduce Risk of Macular Degeneration

A diet high in omega-3 essential fatty acids, especially from fish such as tuna, offers significant protection against both early and late age-related macular degeneration (AMD), show two studies published in the July 2006 issue of the Archives of Opthalmology.

In age-related macular degeneration, the area at the back of the retina called the macula, which controls fine vision, deteriorates, resulting in central vision loss and even blindness. AMD is the leading cause of blindness in people over 50, affecting more than 30 million people worldwide.

In the first study, Brian Chua and colleagues in Sydney, Australia, utilized data from the Blue Mountains Eye Study, which enrolled 3,654 men and women aged 49 and older between 1992 and 1994. Dietary questionnaires completed by 2,895 participants at the beginning of the study provided information on fatty acid intake.

Participants among the top one-fifth in terms of omega-3-rich fish consumption had a 42% lower risk of early AMD compared to those whose fish intake placed them in the lowest fifth. Enjoying omega-3-rich fish at least once a week provided a a 42% reduction in risk for early AMD.

Eating omega-3-rich fish at least three times a week was associated with a 75% reduction in late AMD.

In the second study, Johanna M. Seddon and colleagues at the Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, looked at modifiable and protective factors for AMD among elderly male twins enrolled in the National Academy of Sciences' National Research Council World War II Veteran Twin Registry. Of the 681 twins examined, 222 were found to have intermediate or late stage AMD, and 459 twins had no signs of AMD.

Current smokers had a 1.9-fold (almost double) increased risk of AMD. Even past smokers' risk was highly elevatedâ€"a 1.7 increase compared to men who never smoked.

Eating more fish, however, greatly reduced AMD risk. Among the men whose fish consumption put them among the top 25% of dietary omega-3 fatty acid intake, risk of AMD was 45% lower compared to those with the lowest fish / omega-3 intake.

Eating fish at least twice a week reduced AMD risk by 36% compared to those who ate less than one serving of fish per week.

The authors noted that AMD is highly preventable simply by following a healthy lifestyle: "About a third of the risk of AMD in this twin study cohort could be attributable to cigarette smoking, and about a fifth of the cases were estimated as preventable with higher fish and omega-3 fatty acid dietary intake."

Fend Off Dry Eyes

Dry eye syndrome (DES) afflicts more than 10 million Americans. Artificial tears offer only temporary relief. Expensive prescription drugs promise help, but at the cost of potentially serious side effects.

Could Mother Nature provide a cure? Yes, suggests research published in the October 2005 issue of the American Journal of Clinical Nutrition involving nearly 40,000 female health professionals aged 45-84 enrolled in the Women's Health Study.

Researcher Biljana Miljanovic, MD, MPH, and colleagues at Brigham and Women's Hospital looked at whether essential fatty acidsâ€"the omega-3 fats (found in high amounts in cold water fish and flaxseeds), and the omega-6 fats (found in red meat, safflower, sunflower, soy and corn oils)â€"play a role.

They do. Women whose diets provided the highest amounts of omega-3 fatty acids had a 17% lower risk of dry eye syndrome compared with those consuming the least of these beneficial fats.

In contrast, a diet high in omega-6 fats, but low in omega-3s, significantly increased DES risk. Women whose diets supplied a high ratio of omega-6 to omega-3 fatty acids had a 2.5-fold higher risk of DES syndrome compared to those with a more balanced intake of fatty acids.

Researchers specifically looked at eating tuna fishâ€"a main source of omega-3 fatty acids in the American diet.

Compared with women eating less than one 4-ounce serving of tuna a week:

Women who ate 2 to 4 servings of tuna per week had a 19% lower risk of DES.
Women eating 5 to 6 servings of tuna per week had a 68% lower risk of DES.

"These findings suggest that increasing dietary intake of omega-3 fatty acids may reduce the risk of dry eye syndrome, an important and prevalent cause of ocular complaints," Miljanovic and colleagues conclude.

In addition to tuna fish, omega-3 fatty acids are richly supplied by other fatty fish (such as salmon, mackerel, halibut, sardines, and herring), flaxseeds and flaxseed oil. Due to concerns about mercury levels in tuna, to lower your risk of DES we recommend enjoying a variety of cold-water fish and adding flaxseeds and flaxseed oil to your Healthiest Way of Eating.

Prevent Mental Decline and Alzheimer's Disease by Enjoying Fish

Can eating fish, which is high in DHA and EPA, help lessen the cognitive decline and Alzheimer's disease growing in our aging population? A number of recent studies indicate the answer to this question is a resounding "Yes."

A report from the Framingham Heart Study published in the Archives of Neurology showed that persons whose blood levels of DHA placed them in the top quartile of values had a significantly (47%) lower risk of developing all-cause dementia than did those in the bottom quartile. Plus, greater protection against cognitive decline was obtained from consuming 2.9 than 1.3 fish meals per week. (Schaefer EJ, Bongard V, et al.).

Now, three additional positive studies have been published in the American Journal of Clinical Nutrition:

In the Zutphen Elderly Study, which involved 210 men aged 70-89 years (van Gelder BM, Tijhuis M, et al.), a linear relation was found between the estimated intake of DHA and EPA and prevention of cognitive decline.

A DHA+EPA intake of approximately 380 mg per day seemed to prevent cognitive decline. This amount of DHA+EPA would be found in just 20 grams (just 2/3 of one ounce) of Chinook salmon or in 100 grams (about 3 ounces) of cod.

Eating just two to three meals of fish a week would supply approximately 380 mg EPA+DHA per day.

In the Minneapolis study (Beydoun MA, Kaufman JS et al.) of 2251 men and women, risk of cognitive decline increased as levels of omega-6 (arachidonic acid) increased in subjects' cholesterol and other blood lipids, but decreased as the concentration of omega-3 fat (linoleic acid) increased in their blood fats.

Among subjects with high blood pressure and high cholesterol, cognitive decline was clearly associated with lower blood levels of omega-3 fats (DHA+EPA).

In the Hordaland Health Study, 2,031 adults (55% women) aged 70-74, underwent a battery of cognitive tests including the Kendrick Object Learning Test, Trail Making Test (part A), modified versions of the Digit Symbol Test, Block Design, Mini-Mental State Examination, and the Controlled Oral Word Association Test.

Subjects eating an average of at least 10 grams of fish a day (1 ounce = 30 grams, so eating just 2.1 ounces of fish each week would supply an average of 10 grams daily) had significantly better mean test scores and a lower prevalence of poor cognitive performance than those whose intake averaged less than 10 grams/day.

The associations between total seafood intake and cognition were strongly dose-dependent with maximum benefit observed at an intake of approximately 75 grams/day (this would translate to 2.5 ounces of fish per day or approximately four 4-ounce servings of fish per week). Almost all cognitive functions were beneficially influenced by eating fish, particularly nonprocessed lean fish and fatty fish. (Nurk E, Drevon CA, et al., Am J Clin Nutr.)

In all of these studies, fish consumption and the resulting increase in blood levels of omega-3 fatty acids significantly lessened mental decline over time.

How? A number of mechanisms have been suggested in recent studies to explain fish's protective effects against cognitive decline and Alzheimer's:

EPA's anti-clotting and anti-inflammatory actions promote a healthy blood supply to the brain and lower inflammation.
Since EPA and arachidonic acid are metabolized by the same enzymes, an increase in levels of EPA helps lessen the production of the pro-inflammatory compounds derived from arachidonic acid. (Arachidonic acid is a precursor of proinflammatory cytokines eicosanoids that are thought to be associated with greater cognitive decline.)
Increasing consumption of DHA may correct the DHA deficiency in the cerebral cortex characteristically seen in patients with Alzheimer disease.
DHA is involved in the membrane of ion channels in the brain, making it easier for them to change shape and transmit electrical signals.
DHA is the source of an anti-inflammatory compound made in the brain called NPD1 that lessens amyloid-beta production in cytokine-stressed human brain cells.
DHA slows the accumulation of tau, a protein involved in the development of neurofibrillary tangles, and also decreases beta amyloid formation by reducing levels of presenilin, the enzyme that separates beta amyloid from its parent protein. (Neurofibrillary tangles and beta amyloid plaques are the two types of brain lesions seen in Alzheimer's disease.)

Frank LaFerla, co-author of research published in the Journal of Neuroscience showing that DHA helps prevent the formation of neurofibrillary tangles and decreases beta amyloid formation, commented: "We are greatly excited by these results, which show us that simple changes in diet can positively alter the way the brain works and lead to protection from Alzheimer's disease pathology."

Practical Tip: To keep your cognitive edge, cut back on sources of omega-6 fats, such as beef, and corn, palm, peanut, safflower and sunflower oils, and enjoy omega-3-rich cold water fish, such as snapper, at least 3 times each week.

Tuna's rich content of niacin may also help provide protection against age-related mental decline and Alzheimer's disease, according to research published in the Journal of Neurology, Neurosurgery and Psychiatry.

Researchers from the Chicago Health and Aging Project interviewed 3,718 Chicago residents aged 65 or older about their diet, then tested their cognitive abilities over the following six years.

Those getting the most niacin from foods (22 mg per day) were 70% less likely to have developed Alzheimer's disease than those consuming the least (about 13 mg daily), and their rate of age-related cognitive decline was significantly less.

Omega-3 Fat, DHA, Destroys Alzheimer's Plaques

DHA boosts production of the protein LR11, which destroys the beta-amyloid plaques associated with Alzheimer's disease, shows brain cell research.

"Because reduced LR11 is known to increase beta-amyloid production and may be a significant genetic cause of late-onset Alzheimer's disease (LOAD), our results indicate that DHA increases in LR11 levels may play an important role in preventing LOAD," wrote the researchers in the Journal of Neuroscience.

"Genetic polymorphisms that reduce LR11 expression are associated with increased AD risk," explained the researchers. "However these polymorphisms account for only a fraction of cases with LR11 deficits, suggesting involvement of environmental factors."

The new research investigated if fish oil and DHA could boost LR11 levels, since having high levels of LR11 have been reported to prevent plaque formation, while low levels in patients are believed to be a factor in causing the disease.

Even low doses of DHA increased the levels of LR11 in rat brain cells. Dietary DHA increased LR11 levels in the brains of rats or older mice genetically engineered to develop Alzheimer's disease. The positive effects of DHA on LR11 levels and the protection against Alzheimer's was again seen human brain cells were used. (Ma QL, Teter B, et al. J Neurosci.)

As a result of these findings, the National Institutes of Health has begun a large-scale clinical trial with DHA in patients with well established Alzheimer's disease. Lead researcher, Greg Cole, associate director of UCLA's Alzheimer Disease Research Center, thinks it may be too late for DHA to benefit these patients, but that DHA is highly likely to benefit patients in the earliest stages of Alzheimer's. And, we would add, help prevent the development of the disease in the rest of us!

DHA is the most abundant essential fatty acid in the brain, is crucial for healthy brain development, and low levels have been linked to cognitive impairment. According to the national Alzheimer's Association, approximately 5.1 million Americans suffer from Alzheimer's disease, a number that is projected to increase to 11 to 16 million sufferers by 2050.

Practical Tip: Enjoying several weekly servings of fish high in DHA, such as halibut, is a smart move.

Omega-3-Rich Diet Improves Mood, Reduces Depression

When researchers from Ohio State University evaluated blood samples taken from 43 older adults (average age 67), they found that study participants with high ratios of omega-6 to omega-3 not only had higher levels of various compounds involved in inflammation, but were more likely to suffer from depression.

Both depression and stress promote the production of pro-inflammatory cytokines. Researchers measured a number of these pro-inflammatory compounds including tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and the IL-6 soluble receptor (sIL-6r). Symptoms of depression were assessed using the Center for Epidemiological Studies Depression Scale.

Levels of pro-inflammatory cytokines increased progressively as depressive symptoms increased. But when depressive symptoms were combined with high omega-6:omega-3 ratios, levels of proinflammatory cytokines skyrocketed by up to 40% more than normal -- far beyond the 18% increase resulting from the presence depressive symptoms alone.

Chronic inflammation has already been linked to heart disease, type 2 diabetes, osteoporosis, cognitive decline and Alzheimer's. Earlier epidemiological (population) studies have also linked higher levels of pro-inflammatory cytokines with depressive symptoms. This new study suggests that a diet that is rich in omega-6 fats but includes few of the foods rich in omega-3 fatsâ€"such as the standard American dietâ€"promotes not only inflammation, but depression.

The positive take-away is that increasing consumption of foods rich in omega-3s, while decreasing consumption of omega-6-rich foods, can provide some protection against depression, particularly as depressive symptoms increase.

Omega-3s are polyunsaturated fatty acids found in cold water fish, nuts, such as walnuts, and flaxseeds. Alpha-linolenic acid (ALA), the omega-3 in nuts and seeds, can be convertedâ€"albeit inefficientlyâ€" in the body to the omega-3s found in fish, eicosapentaenoic acid (EPA) and docosahexaenioc acid (DHA).

EPA improves blood flow and is also suggested to affect hormones and the immune system, both of which have a direct effect on brain function. DHA is active in the membrane of ion channels in the brain, making it easier for them to change shape and transmit electrical signals, and is involved in serotonin metabolism (reduced serotonin production and/or activity is a key factor in depression).

Practical Tip: Be of good cheer. Cut back on sources of omega-6 fats, such as beef, and corn, palm, peanut, safflower and sunflower oils. Enjoy a handful of omega-3-rich walnuts and/or flaxseeds daily, and a serving of cold water fish, such as tuna, at least 3 times each week.

Description

Tuna fish is one of the most loved fishes in the world, thanks in part to the popularity of canned tuna. Yet, while canned tuna is a delicious and nutritious food, if you have never tried fresh tuna, you have been missing out on an even healthier culinary treat since fresh tuna retains more of its beneficial omega-3 fats than canned.

Tuna is firm and dense and has the meatiest flavor and texture of any fish.

There are several varieties of tuna including yellowfin and albacore. Yellowfin is deep red in color, while albacore is pale pink. Oftentimes, the tuna will be streaked with dark brown flesh that has a stronger and more intense flavor.

We do not recommend purchasing bluefin tuna due to its being overfished and now being a potentially endangered species.

History

People have been enjoying tuna as a food ever since this beautiful fish appeared in the Earth's waters--basically, since time immemorial.

While fresh tuna has been enjoyed by seacoastal populations throughout history, tuna in other forms of preparation has also been popular. In ancient times, smoked and pickled tuna were widely enjoyed. Today, canned tunafish is extremely popular throughout the world and in the United States, in which canned tuna is the most widely consumed fish of all.

Tuna is found in the warm water areas of the Pacific, Atlantic and Indian Oceans as well as the Mediterranean Sea.

How to Select and Store

Tuna is sold in many different forms. It is available fresh as steaks, fillets or pieces. Tuna is probably best known in its canned form.

Just as with any seafood, it is best to purchase fresh tuna from a store that has a good reputation for having a frequent supply of fresh fish. Get to know a fishmonger (the person who sells the fish) at the store, so you can have a trusted resource from whom you can purchase your fish with confidence.

Fresh whole tuna should be displayed buried in ice, while fillets and steaks should be placed on top of the ice. Try to avoid purchasing tuna that has dry or brown spots.

Smell is a good indicator of freshness. Since a slightly "off" smell cannot be detected through plastic, if you have the option, purchase displayed fish as opposed to pieces that are prepackaged. Once the fishmonger wraps and hands you the fish that you have selected, smell it through the paper wrapping and return it if it has a truly strong fishy odor.

Canned tuna is available either solid or in chunks, and is packaged in oil, broth or water. Although the tuna packed in oil is usually the moistest, it also has the highest fat content, and the oils in which it is packed are high in omega-6 fats. Since omega-6s and omega-3s compete for the same enzymes that activate them for use in the body, and most Americans already consume too many omega-6 fats in comparison to omega-3s, it is best to purchase tuna packed in water or broth. Oftentimes, canned tunas do not distinguish which specific species was used except to note that it is either light tuna (bluefin or yellowfin) or white tuna (usually albacore).

When storing all types of fresh seafood, including tuna, it is important to keep them cold since fish spoils quickly and is very sensitive to temperature. Therefore, after purchasing tuna or other fish refrigerate it as soon as possible. If the fish is going to accompany you during a day full of errands, keep a cooler in the car where you can place your tuna to make sure it stays cold and does not spoil.

The temperature of most refrigerators is slightly warmer than ideal for storing fish. To ensure maximum freshness and quality, it is important to use special storage methods to create the optimal temperature for holding the fish. One of the easiest ways to do this is to place fish, which has been well wrapped, in a baking dish filled with ice. The baking dish and fish should then be placed on the bottom shelf of the refrigerator, which is its coolest area. Replenish the ice one or two times per day.

The length of time that tuna can stay fresh stored this way depends upon how fresh it is, i.e. when it was caught. Fish that was caught the day before you purchased it can be stored for about four days, while fish that was caught the week before can only be stored for about one or two days.

You can extend the shelf life of tuna by freezing it. To do so, wrap it well in plastic and place it in the coldest part of the freezer where it will keep for about two to three weeks.

How to Enjoy

For some of our favorite recipes, click Recipes.

Tips for Preparing Tuna:

After you unwrap your fish, rinse it under cool running water, then pat dry before cooking.

A Few Quick Serving Ideas:

Tuna is a featured ingredient in the classic French dish, Salad Nicoise, which pairs tuna fish with steamed green beans and potatoes.

The sky's the limit when making tuna salad since so many different ingredients nicely complement tuna's mild flavor. Some of our favorite tuna salad ingredients include olives, chili peppers, leeks, fennel and walnuts. Try using fresh lemon juice, olive oil, and a little mustard for a healthier way to make a tuna sandwich instead of mayonnaise. Stovetop Sear a tuna steak and add it to a salad of mixed greens and vegetables.

For an Asian-inspired meal with a hot streak, lightly brush a tuna steak with wasabi and soy sauce, and Quick Broil.

Individual Concerns

The U.S. Food and Drug Administration has advised that pregnant women and women of childbearing age who might become pregnant not eat certain fish, including shark, swordfish, king mackerel and tilefish. It also recommends that nursing mothers and young children steer clear of these fish.

Two groups, the Environmental Working Group and the U.S. Public Interest Group have asked the FDA to add Gulf coast oysters and eight more types of fish to the list including tuna, sea bass, halibut, marlin, pike and white croaker. Their recommendations are based on a report on mercury contamination in fish. In addition, their report says canned tuna, mahi-mahi, cod and pollack should not be eaten more than once a month.

Canned tuna, according to one study in 1991, was contaminated with mercury on average of 170 ppb (parts per billion) to levels of 750 ppb (parts per billion). Food contaminated with mercury, when coupled with other metabolic processes, can trigger human T cells (a type of immune cell) into programmed cell death. Low levels of mercury in the brain have been associated with neurotoxicity.

According to these two research groups, fish considered safe for pregnant women include farm-raised trout and catfish, shrimp, fish sticks, flounder (summer), wild Pacific salmon, croaker, mid-Atlantic blue crab, and haddock.

In 2004, the U.S. Food and Drug Administration issued a recommendation that pregnant and nursing women, women of childbearing age and young children consume no more than six ounces of canned albacore tuna per week. Click here to read more about safety issues regarding tuna and mercury.

Tuna and Purines

Tuna contain naturally-occurring substances called purines. Purines are commonly found in plants, animals, and humans. In some individuals who are susceptible to purine-related problems, excessive intake of these substances can cause health problems. Since purines can be broken down to form uric acid, excess accumulation of purines in the body can lead to excess accumulation of uric acid. The health condition called "gout" and the formation of kidney stones from uric acid are two examples of uric acid-related problems that can be related to excessive intake of purine-containing foods. For this reason, individuals with kidney problems or gout may want to limit or avoid intake of purine-containing foods such as tuna.

Allergic Reactions to Fish

Although allergic reactions can occur to virtually any food, research studies on food allergy consistently report more problems with some foods than with others. It's important to realize that the frequency of problems varies from country to country and can change significantly along with changes in the food supply or with other manufacturing practices. For example, in several part of the world, including Canada, Japan, and Israel, sesame seed allergy has risen to a level of major concern over the past 10 years.

In the United States, beginning in 2004 with the passage of the Food Allergen Labeling and Consumer Protection Act (FALCPA), food labels have been required to identify the presence of any major food allergens. Since 90% of food allergies in the U.S. have been associated with 8 food types as reported by the U.S. Centers for Disease Control, it is these 8 food types that are considered to be major food allergens in the U.S. and require identification on food labels. The 8 food types classified as major allergens are as follows: (1) wheat, (2) cow's milk, (3) hen's eggs, (4) fish, (5) crustacean shellfish (including shrimp, prawns, lobster and crab); (6) tree nuts (including cashews, almonds, walnuts, pecans, pistachios, Brazil nuts, hazelnuts and chestnuts); (7) peanuts; and ( soy foods.

These foods do not need to be eaten in their pure, isolated form in order to trigger an adverse reaction. For example, yogurt made from cow's milk is also a common allergenic food, even though the cow's milk has been processed and fermented in order to make the yogurt. Ice cream made from cow's milk would be an equally good example.

Food allergy symptoms may sometimes be immediate and specific, and can include skin rash, hives, itching, and eczema; swelling of the lips, tongue, or throat; tingling in the mouth; wheezing or nasal congestion; trouble breathing; and dizziness or lightheadedness. But food allergy symptoms may also be much more general and delayed, and can include fatigue, depression, chronic headache, chronic bowel problems (such as diarrhea or constipation), and insomnia. Because most food allergy symptoms can be caused by a variety of other health problems, it is good practice to seek the help of a healthcare provider when evaluating the role of food allergies in your health.

Nutritional Profile

Tuna is an excellent source of niacin, selenium, and protein. Tuna is also a very good source of vitamin B6 and thiamin. In addition, it is a good source of omega-3 fatty acids, phosphorus, potassium, and magnesium.

For an in-depth nutritional profile click here: Tuna.

In-Depth Nutritional Profile
In addition to the nutrients highlighted in our ratings chart, an in-depth nutritional profile for Tuna is also available. This profile includes information on a full array of nutrients, including carbohydrates, sugar, soluble and insoluble fiber, sodium, vitamins, minerals, fatty acids, amino acids and more.

Introduction to Food Rating System Chart
In order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the nutrients for which this food is either an excellent, very good, or good source (below the chart you will find a table that explains these qualifications). If a nutrient is not listed in the chart, it does not necessarily mean that the food doesn't contain it. It simply means that the nutrient is not provided in a sufficient amount or concentration to meet our rating criteria. (To view this food's in-depth nutritional profile that includes values for dozens of nutrients - not just the ones rated as excellent, very good, or good - please use the link below the chart.) To read this chart accurately, you'll need to glance up in the top left corner where you will find the name of the food and the serving size we used to calculate the food's nutrient composition. This serving size will tell you how much of the food you need to eat to obtain the amount of nutrients found in the chart. Now, returning to the chart itself, you can look next to the nutrient name in order to find the nutrient amount it offers, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration's "Reference Values for Nutrition Labeling." Read more background information and details of our rating system.

Tuna, yellowfin, baked/broiled
4.00 oz-wt
113.40 grams
157.63 calories
Nutrient Amount DV
(%) Nutrient
Density World's Healthiest
Foods Rating
tryptophan 0.38 g 118.8 13.6 excellent
selenium 53.07 mcg 75.8 8.7 excellent
protein 33.99 g 68.0 7.8 excellent
vitamin B3 (niacin) 13.54 mg 67.7 7.7 excellent
vitamin B6 (pyridoxine) 1.18 mg 59.0 6.7 very good
vitamin B1 (thiamin) 0.57 mg 38.0 4.3 very good
phosphorus 277.83 mg 27.8 3.2 good
potassium 645.25 mg 18.4 2.1 good
magnesium 72.58 mg 18.1 2.1 good
omega 3 fatty acids 0.33 g 13.8 1.6 good
World's Healthiest
Foods Rating Rule
excellent DV>=75% OR Density>=7.6 AND DV>=10%
very good DV>=50% OR Density>=3.4 AND DV>=5%
good DV>=25% OR Density>=1.5 AND DV>=2.5%

In-Depth Nutritional Profile for Tuna