Soybeans Soybeans
The delicious, slightly nutty flavored soybean has been cultivated in China for over 3,000 years but the good news about soy's culinary versatility and exceptional health benefits is a relatively recent phenomenon in the West. Different varieties of this truly amazing legume are available throughout the year.
The soybean is the most widely grown and utilized legume in the world and one of the most well researched, health-promoting foods available today. Like other beans, soybeans grow in pods, featuring edible seeds. While we most often think of them as being green, the seeds can also be yellow, brown or black.
Food Chart
This chart graphically details the %DV that a serving of Soybeans 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 Soybeans can be found in the Food Rating System Chart. A link that takes you to the In-Depth Nutritional Profile for Soybeans, 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
The soybean is the most widely grown and utilized legume in the world, with the U.S. being responsible for more than 50% of the world's production of this important food. Soy is one the most widely researched, health-promoting foods around. Soybeans' key benefits are related to their excellent protein content, their high levels of essential fatty acids, numerous vitamins and minerals, their isoflavones, and their fiber. While a complete review of all the benefits soybeans offer could easily fill a large book, recently there has been controversy as to the extent to which soybeans are a health-promoting food; we address this issue in our Q+A Are there special concerns related to soy foods?
A Health-Promoting Meat Replacer
Soybeans are regarded as equal in protein quality to animal foods. Just one cup of soybeans provides 57.2% of the Daily Value (DV) for protein for less than 300 calories and only 2.2 grams of saturated fat. Plus, soy protein tends to lower cholesterol levels, while consuming protein from animal sources tends to raise them, since they also include saturated fat and cholesterol. In addition to healthy protein, some of soybeans' nutritional high points include a good deal of well-absorbed iron: 49.1% of the DV for iron in that same cup of soybeans; plus 37.0% of the DV for Nature's relaxant, magnesium; and 41.2% of the DV for essential omega-3 fatty acids.
Stay Lean with Soy
A study published in Endocrinology suggests active isoflavone compounds found in soy, specifically, genistein, may help us stay lean by causing us to produce fewer and smaller fat cells. In this study, laboratory animals eating diets that provided between 500-1500 ppm (parts per million) of genistein created less and smaller fat cells than the animals eating regular chow. In the animals eating soy, decreases in fat production were significant, ranging from 37% to 57% less than the amount of fat produced by mice given standard chow.
In human terms, a comparable amount of genistein to that the animals were given could easily be consumed by simply including traditional soyfoods as part of a healthy whole foods eating plan since most traditional soyfoods, such as tofu, soy milk, tempeh, and miso, are rich sources of isoflavones, providing about 30 to 40 milligrams per serving. Only two soy products, soy sauce and soybean oil, do not contain isoflavones. In one study, genistein concentration was found to be 93 micrograms per gram in nonzukuri miso; 193 micrograms per gram in tempeh; and 223 micrograms per gram in fermented bean curd.
Soy Lowers Blood Pressure and Cholesterol in Men
Soy��s beneficial effects have often been studied in women. Now, a study published in the Journal of the American College of Nutrition has investigated the effects of soy protein and soy isoflavones on blood pressure and cholesterol levels in 61 middle-aged men, at high risk of developing coronary heart disease. For five weeks, half the men consumed diets containing at least 20 grams of soy protein and 80 milligrams of soy isoflavones each day. The effects on their blood pressure, cholesterol levels, and urinary excretion of isoflavones were measured, and then compared to those of the other half of the men who were given a placebo diet containing olive oil.
The men consuming soy in their diet were found to have significant reductions in both diastolic and systolic blood pressure. Not only was their total blood cholesterol significantly lower, but their levels of HDL (good) cholesterol significantly increased. While the control group consuming the soy-free diet containing olive oil also experienced an increase in their HDL cholesterol levels, their blood pressure was not affected, nor did their levels of LDL (potentially harmful) cholesterol drop.
The researchers concluded that daily intake of at least 20 grams of soy protein including 80 mg of isoflavones for a minimum of 5 weeks would be effective in reducing the risk of cardiovascular disease in high-risk, middle-aged men.
Beneficial Effects on Cholesterol Levels and Platelets
Soy protein has been found in recent years to be excellent for a number of different conditions, one of the most important ones being heart disease. Soy protein has been shown in some studies to be able to lower total cholesterol levels by 30% and to lower LDL, or "bad" cholesterol, levels by as much as 35-40%. This is important because high levels of cholesterol, especially LDL cholesterol, tend to become deposited into the walls of blood vessels, forming hard plaques. If these plaques grow too large or break, they can cause a heart attack or stroke.
Some studies have even shown that soy protein may be able to raise HDL cholesterol levels. HDL cholesterol travels through the body collecting the cholesterol that has been deposited in the arteries, so it can be taken away and removed by the liver. One of the main goals of atherosclerosis treatment and prevention, therefore, is to lower LDL cholesterol levels while raising HDL levels. And soy is one food that may be able to do both at once.
In addition, soybeans also contain very good amounts of fiber. When eaten, the fiber in soybeans binds to fats and cholesterol in food, so less is absorbed. In addition, soybeans' fiber binds to bile salts and removes them from the body. Since the liver gets rid of cholesterol by transforming it into bile salts, their removal by fiber forces the liver to use more cholesterol to form more bile salts, leading to lower cholesterol levels overall.
Soy protein has also been shown to reduce the stickiness of platelets, possibly because soybeans are a good source of the important essential fats called the omega-3 fatty acids. When platelets get overly sticky, which happens often in atherosclerosis patients, they are more likely to clump together to form blood clots. These blood clots can in turn lead to heart attacks or stroke. Reducing the risk of these blood clots is just another way that soybeans can protect against these events.
Yet another way in which soy provides cardiovascular protection is by promoting the production of prostacyclin, a potent natural inhibitor of platelet aggregation and a powerful blood vessel wall dilator. A study published in Acta Obstetrics and Gynecology Scandavia suggests that soy's isoflavones also contribute to its beneficial cardiovascular effects. The reason behind isoflavone's beneficial dilatory action on blood vessels is that the endothelium, the lining of blood vessel walls, contains estrogen receptors, which, when triggered, boost prostacyclin production. In this study, 25 healthy postmenopausal women with mild climacteric symptoms were given 55 mg of isoflavones derived from soy and red clover daily for 6 months. After 3 months, the women's endothelial prostacyclin production had increased 70% from baseline. After 6 months, their prostacyclin production was up 110%.
Soy Protein Promotes Larger, Less Dangerous LDL
While recent research has confirmed that soy's isoflavones are not the agents responsible for its cholesterol-lowering effects, a study published in the Journal of Nutrition shows that soy protein does lower heart disease risk by increasing the size of LDL cholesterol particles. Small dense LDL is the most dangerous form of cholesterol, while large LDL, especially when accompanied by adequate supplies of HDL is considered much less risky.
In this study, conducted at the Jean Mayer USDA Human Nutrition Center on Aging at Tufts University, researchers found that people who ate diets high in soy protein significantly increased their LDL particle size compared to periods when they ate diets high in animal protein.
Study participants, all of whom had high cholesterol, were given four different diets, each for a period of six weeks: soy protein with no isoflavones, soy protein enriched with isoflavones, animal protein with no added isoflavones, and animal protein with added isoflavones.
While isoflavones had no effect, soy protein consumption resulted in a decrease in the amount of small dense LDL and an increase in larger LDL particles compared to animal protein—a significantly less risky cholesterol profile.
Soy Packs a Double Punch to Knock Down High Cholesterol
A recently discovered bioactive peptide found in soybeans, lunasin is likely to be a key actor in soy's cholesterol-lowering actions. A study in which lunasin was added to human liver cells demonstrated the compound's potential to significantly lower cholesterol two ways -- by inhibiting the expression of the gene responsible for our body's internal production of cholesterol, while also increasing the expression of a gene that reduces levels of LDL cholesterol in the blood.
When added to a cell culture of HepG2 liver cells, lunasin slashed HMG-CoA reducstase expression by 50%. HMG-CoA is the gene that directs production of HMG-CoA reductase, the enzyme responsible for cholesterol biosynthesis. (Statin drugs also lower cholesterol by blocking HMG-CoA reductase.)
At the same time, lunasin increased by 60% the expression of the gene which produces LDL cholesterol receptors that help clear plasma cholesterol.To learn more about lunasin, visit
http://www.lunasin.comIncreased Nitric Oxide Production
A study published in the British Journal of Nutrition suggests that soy protein also protects against atherosclerosis by increasing blood levels of nitric oxide, a small molecule known to improve blood vessel dilation and to inhibit oxidative (free radical) damage of cholesterol and the adhesion of white cells to the vascular wall (two important steps in the development of atherosclerotic plaques).
In this study, when researchers gave laboratory animals bred to be apoliprotein-E deficient a purified diet containing either casein, the principal protein in dairy products, soy protein or rice protein, the mice given casein developed the largest atherosclerotic lesions. (In humans as well as animals, apolipoprotein E plays an important role in cholesterol transport, so a deficiency of this protein increases risk for the development of atherosclerosis.) Animals given soy or rice protein fared much better.
In trying to understand why, the researchers evaluated blood levels of nitric oxide. Mice fed either soy or rice protein diets were found to have increased blood levels of L-arginine (the amino acid that the body uses to produce nitric oxide) and nitric oxide metabolites when compared to those given casein-based feed. However, the L-arginine content of the soy and rice diets was not high enough to explain the amount of protective benefit they conferred, so the researchers concluded that these foods must also contain other protective compounds.
Whole Soyfood, But Not Isolated Isoflavones, Found Cardioprotective
Research published in Arteriosclerosis Thrombosis and Vascular Biology suggests that while a diet rich in soy foods may be cardioprotective, soy isoflavones by themselves will not produce much effect. At the conclusion of this animal study, those eating the soy protein had 50% less damaged LDL (bad cholesterol) in their coronary arteries compared to those given either the milk-based diet or the milk-based diet supplemented with isoflavones. Researchers noted that the reduced LDL cholesterol seen in the carotid arteries with soy was due to decreased delivery of LDL to the arteries, which could partly explain the soy's cardioprotective effects. Once again, it appears that the combination of nutrients Mother Nature supplies in whole foods is better calibrated to promote health than are components of whole foods extracted from the matrix in which they function as part of a comprehensive whole.
Whole Soyfoods, But Not Isolated Isoflavones, Significantly Lower Cholesterol
Once again, studies show that eating whole foods, which naturally provide their own unique combination of nutrients, does more for your health than using supplements.
A meta-analysis of 23 studies published from 1995 to 2002, which appeared in the American Journal of Clinical Nutrition, shows that consumption of soy protein—with its isoflavones intact as it is supplied in soyfoods—results in significant decreases in total cholesterol(by 0.22 mmol/L, or 3.77%), LDL (bad) cholesterol (by 0.21 mmol/L, or 5.25%), and triglycerides (by 0.10 mmol/L, or 7.27%), plus significant increases in HDL (good) cholesterol (by 0.04 mmol/L, or 3.03%).
Reductions in total and LDL cholesterol were even larger in men than women, and subjects with high cholesterol benefited the most. Studies in which particpants consumed more than 80 mg of soy protein containing isoflavones daily resulted in better effects on the lipid profile (a person's LDL, HDL and triglycerides).
The strongest lowering effects of soy protein containing isoflavones on total cholesterol, LDL cholesterol, and triglycerides occurred within the first few weeks, while improvements in HDL cholesterol were only seen in studies lasting more than 12 weeks.
In contrast, tablets containing extracted soy isoflavones did not produce a significant effect on total cholesterol reduction.
Special Benefits for Women's Hearts and Bones
Soy foods may offer special benefits for the hearts and bones of premenopausal women, suggest two studies conducted at Wake Forest University Baptist Medical Center and presented at the 2004 annual meeting of the North American Menopause Society, Washington, D.C. The results of these studies indicate a beneficial synergy between isoflavones, the weakly estrogenic compounds in soy, and the body's own estrogen in decreasing cholesterol and increasing bone mass.
In the first study, cholesterol levels in laboratory animals fed a soy-based diet were improved compared to those of monkeys given a diet of milk and animal protein—and the most improvement occurred in those animals at highest risk for heart vessel disease. A low ratio of total cholesterol to HDL (good) cholesterol is considered healthier. In animals at highest risk for heart disease, the cholesterol ratio decreased by 48% in those given soy compared to those receiving milk and animal protein. Even in the animals at low risk for atherosclerosis that ate soy, the cholesterol ratio dropped 33%.
Lead researcher in this study, Jay Kaplan, PhD, noted that a 48% drop in the cholesterol ratio would likely equate to a 50% reduction in the size of plaques in the arteries, which can rupture causing heart attacks and strokes.
In the second study, animals eating soy were found to have an increase in bone mass compared to those not given soy. According to lead researcher in this study, Cynthia Lees, D.V.M., Ph.D., "The increase was small, but this suggests the possibility that if women consumed soy on a regular basis before menopause, it could benefit their health after menopause." Kaplan also noted that because the soy-estrogen combination caused improvements in both cholesterol and bone, it might also positively impact other areas of the body affected by estrogen, including the brain.
Next on the researchers' agenda will be a study using lower levels of isoflavones over a longer period of time to see if this will be as effective—an outcome that appears to already be supported in a human trial published in the American Journal of Clinical Nutrition.
In this study, which included over 1000 pre- and postmenopausal women (meat-eaters, vegetarians, and vegans), eating moderate amounts of soy foods as part of a regular diet was associated with a lower ratio of total to LDL cholesterol, but not with a lowering in the level of beneficial HDL cholesterol. In those women eating 6 or more grams of soy protein daily, blood levels of LDL cholesterol were 12.4% lower than those in women who ate less than 0.5 grams of soy protein daily.
Soy Protects Menopausal Women's Bones
Two meta-analyses of randomized clinical trials, one considering 9 studies involving a total of 432 subjects, and the other reviewing 10 studies with a total of 608 subjects, have shown that consuming isoflavone-containing soy foods significantly inhibits bone loss and stimulates bone formation in menopausal women.
The first meta-analysis, published in the European Journal of Clinical Nutrition found that women whose daily diets provided soy isoflavones had much lower amounts of deoxypyridinoline (Dpyr, a bone resorption marker) in their urine, and much higher amounts of bone-specific alkaline phosphatase (BAP, a bone formation marker) in their blood. And these bone-protective effects occurred even if the women were consuming less than 90 mg of soy isoflavones per day or if the intervention lasted less than 12 weeks. (Ma DF, Qin LQ, et al.)
The second meta-analysis, published in Clinical Nutrition found that bone mineral density increased significantly (+27 mg/cm) in the spine of women whose diets provided soy isoflavones, even in amounts less than 90 mg/day, compared to those who did not. When more than 90 mg/day of isoflavones from soy foods was consumed for at least 6 months, improvements in spine bone mineral density became even more significant, increasing 28.5mg/cm. (Ma DF, Qin LQ, et al.)
Practical Tip: Enjoying soy foods daily for just 6 months can be enough to exert beneficial effects on bone in menopausal women. All the traditional soyfoods (tofu, soy milk, tempeh and miso) provide 30 to 40 mg per serving. Roasted soybeans are an especially good source; just one-half cup contains 167 mg of isoflavones. However, neither soy sauce nor soy oil contain isoflavones.
Soy Foods Protect Post-Menopausal Women against Cardiovascular Disease
Women's risk for cardiovascular disease increases after menopause, in part because levels of risk factors including homocysteine and excess body iron, tend to rise.
In this study (Hanson L, Engleman H, American Journal of Clinical Nutrition), researchers looked at the effect of soy protein, specifically soy's isoflavones and phytate, on CVD risk factors in 55 postmenopausal women. To do so, they randomly assigned the women to 1 of 4 soy protein (40 grams per day) groups: soy containing both its native phytate and native isoflavones, native phytate but low isoflavone, low phytate and native isoflavone, or low phytate and low isoflavone.
After just 6 weeks, women in the groups given soy protein with its native phytate had significant reductions in homocysteine and excess iron concentrations. Soy protein with native isoflavones had no effect.
Most interesting about this study is the fact that the phytate in soy, a compound which, because of its mineral-binding effects, has sometimes been considered problematic, that is responsible for some of the CVD-protective effects soy offers postmenopausal women. Once again, Mother Nature appears to have good reason for all the compounds found in whole foods.
Soy Nuts Lower Blood Pressure and LDL Cholesterol, plus Decrease Menopausal Symptoms in Postmenopausal Women
Soy nuts have a lot to offer postmenopausal women, suggest two studies conducted by Francine Welty and her team from the Beth Israel Deaconess Medical Center, Boston.
Enjoying a half-cup of soy nuts as one source of protein in a healthy diet can reduce blood pressure and LDL cholesterol levels in postmenopausal women by as much as 10% in just 8 weeks, discovered Welty's team in research they published in the Archives of Internal Medicine (Welty FK, Lee KS, et al.)
High blood pressure (hypertension) is defined as having blood pressure higher than 140/90 mmHg, and is a major risk factor for cardiovascular disease, a leading cause of death in postmenopausal women.
In this 16-week study, 60 postmenopausal women (average age 56), 12 of whom had high blood pressure, followed two different diets, each for 8 weeks: a Therapeutic Lifestyle Changes (TLC) diet or a TLC diet in which soy nuts (roasted, unsalted soybeans) were used as one source of protein. Blood samples and blood pressure measurements were taken at the beginning and end of each 8-week diet.
The TLC diet derived 30% of its calories from fat (with 7% or less from saturated fat), 15% from protein and 55% from carbohydrates. The diet delivered 1,200 mg of calcium and less than 200 mg of cholesterol daily. Two meals of fatty fish, such as salmon or tuna, were included weekly.
The TLC with soy diet contained the same calorie, fat and protein, calcium and cholesterol content, but 25 grams of its protein were delivered in the form of one-half cup of unsalted soy nuts.
When eating the soy nuts as part of their TLC diet, the women with high blood pressure experienced systolic and diastolic blood pressure reductions of 9.9% and 6.8%, respectively, and even those with normal blood pressure experienced reductions and 5.2% and 2.9%, respectively.
Not only was blood pressure lowered in all the women, but in those who began the study with high blood pressure, LDL cholesterol and apoB levels also dropped, 11% and 8% respectively, compared with the TLC diet without soy. (LDL, sometimes called "bad" cholesterol is a major risk factor for cardiovascular disease, and apoB is a carrier for LDL, so lower levels mean that less LDL is being carried in the bloodstream.)
"A 12-millimeter of mercury decrease in systolic blood pressure for 10 years has been estimated to prevent one death for every 11 patients with stage one hypertension treated; therefore, the average reduction of 9.9 milligrams of mercury in systolic blood pressure in hypertensive women in the present study could have significant implications for reducing cardiovascular risk and death on a population basis," wrote Welty.
Triglyceride levels also dropped in all the women when eating soy nuts, 7% in those with normal and 11% in those with high blood pressure. (High triglycerides, a form in which fat is carried in the bloodstream, are another cardiovascular disease risk factor.)
"Although these reductions were not statistically significant, their magnitude is similar to reductions in triglyceride levels observed in other soy studies and may have clinical relevance, especially since triglyceride levels are stronger predictors of cardiovascular risk in women than in men," noted Welty.
The researchers speculate that soy isoflavones work synergistically with other compounds in soy nuts, which are roasted whole soy beans, to produce the blood pressure lowering effects. In other studies, in which isoflavones were given in isolation in the form of supplements, no such benefits were observed.
"This study was performed in the free-living state; therefore, dietary soy may be a practical, safe and inexpensive modality to reduce blood pressure. If the findings are repeated in a larger group they may have important implications for reducing cardiovascular risk in postmenopausal women on a population basis," concluded the researchers.
In a similar 16-week diet crossover study, this one looking at menopausal symptoms, Welty's team again gave 60 healthy postmenopausal women two 8-week diets, the TLC diet and a TLC diet with similar calorie, fat, and protein content in which one-half cup soy nuts divided into three or four portions spaced throughout the day (containing 25 g soy protein and 101 mg isoflavones) replaced 25 grms of non-soy protein.(Welty FK, Lee KS, et al, J Women's Health).
Once again, compared with the TLC diet alone, women did much better on the TLC diet with soy nuts. While eating soy nuts, hot flashes dropped 45% in women beginning the study with at an average of at least 4.5 hot flashes a day, and 41% in those who began the study with an average of less than 4.5 hot flashes daily.
Eating soy nuts also resulted in significant improvements in the women's scores on the menopausal symptom quality of life questionnaire: a 19% average decrease in vasomotor symptoms score, 12.9% reduction in psychosocial symptoms score, 9.7% decrease in physical symptoms score, and a 17.7% reduction in sexual symptoms score.
Practical Tip: If you're postmenopausal or heading towards menopause, including a half-cup of unsalted soy nuts in your healthy way of eating is an easy, delicious way to lower your blood pressure and LDL cholesterol, while greatly reducing hot flashes and other menopausal symptoms. Divide your soy nuts into 3 or 4 handfuls and use as a snack or a crunchy topping for soups, salads and steamed vegetables.
Soy Foods Do Not Increase Breast Cancer Risk in Postmenopausal Women
Eating soy foods does not increase risk of breast or endometrial cancer in postmenopausal women, and may even be protective, suggests a study published in the Journal of Clinical Endocrinology and Metabolism.
Despite the fact that the isoflavones found in soy have only 1/1,000th the potency of human estrogens, and epidemiological studies indicate that populations the consume diets high in soy have lower rates of breast cancer, the safety of consuming soy has been questioned because hormone replacement therapy has been found to increase breast cancer risk.
(We'd like to point out that the debate has not taken into consideration the fact that conventional hormone replacement therapy has meant the use of estrogens derived from pregnant mares, which are not only different from, but much more potent than human estrogens, and progestin, drug compounds similar but not identical to human progesterone. So, in our opinion, comparing the potency and possible side effects of conventional HRT to that of soy foods is like contrasting Godzilla with Bambi.)
Now, a animal study conducted at Wake Forest University Baptist Medical Center, has found that consuming the amount of soy phytoestrogens that would be ingested when soyfoods are included in the diet (in women, about 129 mg/day of isoflavones) does not increase risk of breast or uterine cancer, and appears to be protective.
In this study, laboratory animals with healthy breast tissue whose ovaries had been removed (to resemble postmenopausal women), were randomly assigned to receive one of three diets for 3 years:
Group One was given soy protein isolate from which the isoflavones had been removed.
Group Two received soy protein isolate containing soy isoflavones in a dose comparable to 129 mg/day, more than most people would get on a soyfoods-rich diet.
Group Three was given soy protein concentrate from which the isoflavones had been removed and replaced with conjugated equine estrogens (Premarin, the equine estrogen commonly used in HRT) in an amount comparable to the usual dose given women, 0.625 mg/day.
The researchers measured a number of markers of cancer risk: breast density, numbers of dividing breast and uterine cells, sex steroid receptor expression, and blood levels of estrogen. In the monkeys receiving Premarin, levels of all cancer markers increased significantly. In contrast, the monkeys given soy with or without its isoflavones had no increase in any of the cancer markers. And animals receiving soy with isoflavones actually had significantly lower levels of estrogen than the animals given soy from which the isoflavones had been removed.
The researchers concluded that the high dietary levels of soy isoflavones did not increase markers related to uterine and breast cancer risk in the laboratory animals studied.
Lead researcher Charles Wood noted that the research addressed the effects of plant estrogens on normal breast tissue, and not in breast cancer. Whether soy is safe for breast cancer survivors remains "a big unanswered question," according to Wood.
Wood's research team has now begun investigating whether soy isoflavones can be used to block breast cell proliferation triggered by estrogen replacement therapy. The theory is that since soy isoflavones, but not estrogens, are similar enough in structure that they can bind to estrogen receptors, they can prevent the much more powerful human estrogen from doing so, thus reducing its effects in the body.
Until this research provides more answers, it looks like soyfoods may, at the very least, reduce cancer risk in postmenopausal women with healthy breast tissue.
Stabilize Blood Sugar at Healthy Levels
Another condition for which soybeans can be very beneficial is diabetes, particularly type 2 diabetes. The protein in soybeans, and also in other legumes, is excellent for diabetic patients, who tend to have problems with animal sources of protein. The protein and fiber in soybeans can also prevent high blood sugar levels and help in keeping blood sugar levels under control. Some diabetics even find that the effects of soybeans and other legumes on blood sugar are so profound that they need to monitor their new blood sugar levels and adjust their medications accordingly. Of course, all of this should only be done under the supervision of a doctor. Diabetes patients are especially susceptible to atherosclerosis and heart disease, which is the number one killer of persons with diabetes. Keeping cholesterol levels low with soybeans may be useful for preventing these heart problems. In addition, soybeans have been shown to lower high triglyceride levels. Triglyceride levels tend to be high in diabetic patients, and high triglyceride levels are another factor of diabetics' increased risk for heart disease.
Several Types of Legumes, and Especially Soybeans, Lower Diabetes Risk
Researchers from Vanderbilt University Medical Center and the Shanghai Cancer Institute recruited 64,227 middle-aged Chinese women with no previous history of diabetes, cardiovascular disease or cancer, and followed them an average of 4.6 years.
Food-frequency questionnaires revealed an inverse association between eating legumes and incidence of type-2 diabetes. A high intake of all legumes resulted in a 38% reduction in risk, while a high intake of soybeans, specifically, was associated with a 47% risk reduction. (Villegas R, Gao YT, et al. Am J Clin Nutr)
Research conducted at the University of Massachusetts Amherst also suggests soy, in the form of soy yogurt, could play an important role in the management of type-2 diabetes and high blood pressure. (Shetty K., UMass Amherst)
Type 2 diabetes can often be accompanied by an abnormal rise in blood sugar right after a meal. Medications to prevent this often target enzymes responsible for modifying carbohydrates before they can be absorbed by the small intestine. Since carbs are the major source of blood sugar, inhibiting carb-altering enzymes α-amylase and β-glucosidase slow the body's absorption of sugars.
High blood pressure is another problem for which diabetics are at increased risk, so the U Mass researchers also took a look at soy yogurt's effects on the activity of angiotensin-I converting enzyme (ACE-I), which plays a role in the constriction of blood vessels and is a target of blood pressure-lowering medications (ACE-inhibitors).
Buying peach, strawberry, blueberry and plain yogurts made by four different brands, including a soy brand, at the local grocery, the researchers took samples of each yogurt and tested its ability to inhibit the three enzymes.
The soy yogurt enriched with blueberries inhibited the activity of all three enzymes. The blueberry (non-soy) yogurts were also best at blocking the action of β-glucosidase. Peach and strawberry enriched yogurts inhibited both carb-altering enzymes, α-amylase and β-glucosidase.
The researchers also tested the yogurts for their phenol content (phenols are potent anti-oxidants and are sometimes even more potent than vitamin antioxidants) and levels of antioxidant activity. Blueberry yogurts had the second-highest concentrations of phenols and the most antioxidant activity, surpassed only by soy (even plain soy yogurt had higher phenol content than any regular yogurt with fruit). Soy yogurts had the highest phenol content overall, and were best at inhibiting ACE-I, lessening its activity by 92%.
The findings provide a strong rationale for further clinical studies, and for incorporating "healthy diet design" into disease management strategies. "What one eats should be part of an overall approach to therapy," said lead researcher Kalidas Shetty.
Practical Tip: Give soy yogurt a try. Instead of buying fruit-flavored yogurt, though, we recommend adding your own fresh blueberries, strawberries or peaches to plain yogurt. You'll get far more fruit and along with it, we expect you'll also get more more carb- and ACE-1-enzyme-inhibiting activity as well.
Protect Against Diabetes-related Kidney and Heart Disease
A small clinical trial conducted on type 2 diabetes patients with nephropathy (diabetes-related kidney damage) suggests that soy protein can help protect diabetics—hearts and kidneys from damage caused by the disease. The study, a randomized crossover clinical trial, was conducted on 14 type 2 diabetes male and female patients receiving medical care at an educational university hospital and private kidney disease clinic. For the first seven weeks, patients followed a diet typically recommended to control nephropathy, which included 0.8 grams/kilogram of protein, based on 70% animal and 30% vegetable protein. After a washout period during which study subjects ate their pre-study diet, they were readmitted for another 7-week cycle, this time consuming a diet containing 35% soy protein and 30% vegetable protein.
Following the soy diet, all patients experienced significant reductions in total cholesterol, triglyceride and LDL-cholesterol, while levels of beneficial HDL cholesterol remained stable and renal function improved. Specifically, the patients' urinary urea nitrogen (a protein component that is not normally leaked into the urine) and proteinuria (protein in the urine, another indicator that the kidneys are beginning to fail) were both much lower on the soy protein diet. Researchers concluded, "Soy inclusion in the diet can modify the risk factors of heart disease and improve kidney function in these patients."
Another study, this one conducted at the University of Illinois and published in the Journal of Nutrition, provides more evidence that soy protein helps persons with diabetes prevent kidney disease and improve their cholesterol profile. This study, a seven month crossover trial, involved 14 men with type 2 diabetes and kidney disease. After the first month, during which baseline measurements were established for each man, they were divided into two groups, one of which received a daily serving of vanilla flavored protein powder made from soy protein while the other group was given protein powder containing casein (the primary protein in cow's milk). After eight weeks, the men were given no protein powder for four weeks and then switched over to the other protein powder for eight weeks. Serving size of both types of protein was 0.5g/kg/day.
While on the soy protein, the men's urinary albumin concentrations decreased by 9.5% but increased by 11.1% while on the casein diet. Higher amounts of albumin in the urine are a marker for deterioration in kidney function.
In addition, blood levels of beneficial HDL-cholesterol increased by 4.3% after the soy protein diet but tended to be lower after casein consumption.
Why were these beneficial effects seen with soy? The authors suggest that soy's isoflavones may be responsible for the improvement in cholesterol profile, while soy's higher levels of the amino acid arginine, a chemical precursor to a molecule called nitric oxide that dilates arteries, are responsible for improving blood flow in the kidney and thus kidney function.
Their conclusion: a simple dietary modification—adding soy protein foods to the diet—could help persons with diabetes prevent kidney disease and improve their cholesterol profile.
Soybeans' Choline Lessens Chronic Inflammation
People whose diets supplied the highest average intake of choline (found in egg yolk and soybeans), and its metabolite betaine (found naturally in vegetables such as beets and spinach), have levels of inflammatory markers at least 20% lower than subjects with the lowest average intakes, report Greek researchers in the American Journal of Clinical Nutrition (Detopoulou P, Panagiotakos DB, et al.)
Compared to those whose diets contained <250 mg/day of choline, subjects whose diets supplied >310 mg of choline daily had, on average:
22% lower concentrations of C-reactive protein
26% lower concentrations of interleukin-6
6% lower concentrations of tumor necrosis factor alpha
Compared to those consuming <260 mg/day of betaine, subjects whose diets provided >360 mg per day of betaine had, on average:
10% lower concentrations of homocysteine
19% lower concentrations of C-reactive protein
12% lower concentrations of tumor necrosis factor alpha
Each of these markers of chronic inflammation has been linked to a wide range of conditions including heart disease, osteoporosis, cognitive decline and Alzheimer's, and type-2 diabetes.
In an accompanying editorial in the American Journal of Clinical Nutrition entitled, "Is there a new component of the Mediterranean diet that reduces inflammation?," Steven Zeisel from the University of North Carolina at Chapel Hill noted that choline and betaine work together in the cellular process of methylation, which is not only responsible for the removal of homocysteine, but is involved in turning off the promoter regions of genes involved in inflammation.
"Exposure to oxidative stress is a potent trigger for inflammation. Betaine is formed from choline within the mitochondria , and this oxidation contributes to mitochondrial redox status ," Zeisel continued.
"If the association between choline and betaine and inflammation can be confirmed in studies of other populations, an interesting new dietary approach may be available for reducing chronic diseases associated with inflammation," he concluded.
Recommended daily intakes of choline were set in 1998 at 550 milligrams per day for men and 425 milligrams a day for women. No RDI has been set for betaine, which, since it is a metabolite of choline, is not considered an essential nutrient.
Practical Tip: Egg yolks are the richest source of choline, followed by soybeans. Spinach, beets and whole wheat products are primary sources of betaine. (Olthof MR, van Vliet T, et al. J Nutr)
Promote Gastrointestinal Health
A substance found in soybeans may reduce colon cancer risk, suggests animal research conducted by Alfred Merrill at Emory University and the Karmanos Cancer Institute.
The cancer-protective substance is a sphingolipid (a type of lipid or fat that, in the body, is primarily used as a constituent of nerve tissue) called soy glucosylceramide. Sphingolipids found in milk have already been shown to inhibit the formation of tumors in laboratory animals exposed to carcinogens known to cause colon cancer. While the sphingolipids found in soy differ structurally from those found in milk, the soy compounds had comparable effects.
When laboratory animals exposed to a carcinogen were given a diet containing 1% soy glucosylceramide, the proliferation of colon cancer cells dropped by 56%. When the same diet was given to a strain of animals bred to spontaneously develop colon cancer, the rate at which tumors formed dropped 37%.
Soy sphingolipids provided this protection by affecting the expression of 96 different genes in the cells that form the lining of the intestines, increasing 32 and decreasing 64. Soy's effects on these genes resulted in a decrease in the production of two factors associated with cancer initiation and promotion: hypoxia-induced factor 1 alpha and transcription factor 4.
While other plants also contain sphingolipids, soy contains relatively high amounts of glucosylceramide, which researchers think may be one reason for the cancer-preventive effects of eating soy foods.
Protection against Prostate Cancer
The incidence of prostate cancer is much lower in Asian than Western populations, and soy foods may be one important reason why, suggests research published in Cancer Epidemiological Biomarkers and Prevention (Kurahashi N, Iwasaki M, et al.)
A 9-year Japanese study involving 43,509 men ranging in age from 45 to 74 years found that those eating the most soy food and miso (and therefore consuming more genistein and daidzein, the isoflavones found in soybeans) had a significantly lower risk of localized prostate cancer.
Among the men who were older than 60, the protective effect was strongest. Men whose diets provided the most genistein had a 48% reduced risk of localized prostate cancer compared to men food delivered the least of this isoflavone. Similarly, men consuming the most daidzein and soy foods showed 50% and 48% reduced risks of localized prostate cancer, respectively, compared to men consuming the least daidzein and soy foods.
Research suggests that isoflavone phytonutrients found in soybeans may protectively alter men's metabolism of estrogen, lowering men's ratio of 2 hydroxy estrogens to 16 hydroxyestrone (2:16 OH-E1). (Yes, real men produce some estrogen, and in men, the prostate is the primary locus of estrogen production.) Since the 2 hydroxy metabolites of estrogen are less likely to initiate hormone-related cancers than estrogen's 16 hydroxyestrone metabolites, soy's effect of increasing the amount of 2 hydroxy estrogen produced in relation to the amount of 16 hydroxyestrone made in the prostate may help prevent prostate cancer. (Hamilton-Reeves JM, Rebello SA, et al., J Nutr.)
Earlier research linking soy to protection against prostate cancer has suggested that the weak estrogenic activity of soy's isoflavones, which may act to reduce testosterone levels and inhibit 5-alpha-reductase (an enzyme involved in converting testosterone to its most potent form, DHT, which has been linked to prostate growth and male baldness), might also be protective. (Kurahashi N, Iwasaki M, et al., Cancer Epidemiol Biomarkers Prev.)
Practical Tips: Protect your prostate health by making soy foods a staple part of your healthy way of eating. Not a fan of tofu? Soy milk is now an available option, even at most espresso stands. You can take packets of miso to work with you, just as you would any dehydrated soup mix. Miso not only makes a delicious broth on its own, but can be sprinkled like seasoning over brown rice or any grain, any soup, or sautéed vegetable to add great flavor. Try a tofu burger for lunch. Experiment with a few brands till you find one you really enjoy; some (we like BocaBurgers) now do a pretty reasonable job of mimicking the taste and texture of beef. Soy nuts can also go with you to the office for a quick snack.
Promote Optimal Health
The fiber in soybeans also provides preventative therapy for several other conditions. Fiber is able to bind to cancer-causing toxins and remove them from the body, so they can't damage colon cells. High-fiber soybeans may be able to help reduce the risk of colon cancer. As a matter of fact, in areas of the world where soybeans are eaten regularly, rates of colon cancer, as well as some other cancers, including breast cancer, tend to be low.
A study published in the Journal of Nutrition suggests that colon cancer may be a hormone-responsive cancer, and that soy protein can not only help prevent its occurrence but can have a very positive effect on the number and size of tumors that do occur. In this study, female laboratory animals whose ovaries had been removed to limit their sources of estrogen were exposed to an agent that causes colon tumors, then fed five different diets designed to compare the effects of specific ingredients, and followed for a year.
Diet One contained milk protein, and Diet Two, soy protein with no isoflavones; both these diets were free of any kind of estrogen. The remaining three diets contain soy protein plus an estrogenic component. Diet Three contained soy protein and the isoflavone, genistein, a phytoestrogen found in soy. Diet Four contained soy plus a mixture of soy-derived isoflavones including genistein, and Diet Five contain estrone, a naturally occurring human estrogen.
While the diet containing estrone was the most effective in preventing colon cancer, all the soy/estrogen diets were also protective and even those animals given soy protein with no estrogen-like factors that did develop colon cancer had fewer and smaller tumors compared to mice given milk protein.
Lead researcher, Ruth MacDonald, professor of food science at the University of Missouri, is now trying to determine how soy compounds protect against colon cancer. Until this work is done, however, she notes that not only is soy protein thought to also be helpful in the prevention of heart disease, but "the good news is that there are many ways to add soy to your diet now, and we know of no harmful side-effects to eating soy protein."
In addition to its fiber, soy's isoflavones also contribute to its protective effect against breast and prostate cancer. Research involving nearly 22,000 Japanese women—the Japan Public Health Center-Based Prospective Study on Cancer and Cardiovascular Diseases—shows that a diet high in isoflavone-rich soy foods, particularly miso, is linked to a significantly lower risk of breast cancer. The women, who ranged in age from 40 to 59 years, filled out a dietary questionnaire that included questions about soy consumption and were followed for 10 years. Whether pre- or postmenopausal, women who reported eating three or more cups of miso soup per day had a 40% lower risk of developing breast cancer compared to women who reported consuming less than one cup per day. Women with the highest intakes of isoflavones—compounds in soyfoods that can bind to estrogen receptors in the body and block out human estrogen, thus lessening its effects—had a 54% lower risk of developing breast cancer compared to those whose intake of isoflavones was lowest.
A variety of soyfoods commonly eaten in the Asian diet contain isoflavones including tofu, miso, soymilk, soy sauce, soy flour, green or dried soybeans, soybean sprouts and a fermented soy food called natto. Almost 75% of the women reported eating miso soup daily, and of these 34% ate three or more cups of miso soup per day. More than 45% reported eating soy foods other than miso daily. The average intake of isoflavones among participants in this study was calculated to be about 700 times higher than that of Caucasians in the United States.
In epidemiological studies, genistein, a naturally occuring isoflavone found chiefly in soybeans, has been consistently linked to lower incidence of prostate cancer. A recent study of human prostate cancer cells demonstrated some of the mechanisms behind genistein's anti-prostate cancer effects. Genistein not only induced chemicals that block cell cycling, thus preventing the proliferation of cancerous cells in the prostate, but at high concentrations actually induced apoptosis, the self-destruct sequence the body uses to eliminate worn out or abnormal cells.
Another study looked at the antioxidant effects of these isoflavones in soy, and found that genistein protected cells in healthy men from an increase in free radical production by inhibiting the activation of an important inflammatory agent called NF-kappaB and by decreasing levels of DNA adducts (a marker of DNA damage).
Subject: Soybeans Soybeans 
Sat Aug 27, 2011 9:21 am
soy foods.