The World's Healthiest Foods
Soybeans

The delicious, slightly nutty flavored soy bean has been cultivated in China for over 13,000 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.

 


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. A complete review of all the benefits soybeans offer could easily fill a large book. Soybeans' key benefits are related to its excellent protein content, its high levels of essential fatty acids, numerous vitamins and minerals, its isoflavones, and its fiber.

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 protein from animal sources tends to raise them. 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 the August 2003 issue of 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, mice eating diets that provided between 500-1500 ppm (parts per million) of genistein created less and smaller fat cells than mice on typical mice chow. In the mice eating soy, decreases in fat production were significant, ranging from 37% to 57% less than the amount of fat produced by mice given standard rat chow.

In human terms, a comparable amount of genistein to that the mice 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.(October 4, 2003)

Soy Lowers Blood Pressure and Cholesterol in Men

Soy’s beneficial effects have often been studied in women. Now, a study published in the February 2004 issue of 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 Scottish men (aged 45 –59 years), 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 miligrams 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.(March 26, 2004)

Increases Heart Rate Variability—A Measure of Heart Muscle Function

Consuming soy or fish oil increases heart rate variability (HRV), a measure of cardiac function, in as little as three weeks, shows the results of a study published in the April 2005 issue of Chest.

Soy oil provides the plant-derived omega 3 fatty acid, ALA, while fish oil contains the marine-derived omega-3 fatty acids, EPA and DHA. These omega-3 fatty acids improve heart function by providing greater variability between beats, therefore reducing 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 g supplement of fish oil and the other half took a daily 2 g supplement of soy oil.

Patients in both groups experienced a significant increase in HRV. While those who took fish oil achieved a greater increase in a shorter time period (within the first 2.7 weeks), within 8.1 weeks for a significant increase in HRV was also 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 only 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 to two months."

"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 soyfoods,salmon or tuna. For recipes certain to not only increase your heart rate variability but also your delight in eating, click Recipes

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 the August 2003 issue of 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%!(October 24, 2003)

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 March issue of 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 (a ratio of 4 LDL:1 HDL is considered ideal) 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. (May 9, 2004)

Increased Nitric Oxide Production

A study published in the July 2003 issue of 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 mice 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.) Mice 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.(September 8, 2003)

Whole Soyfood, But Not Isolated Isoflavones, Found Cardioprotective

Research published in the December 2003 issue of Arteriosclerosis Thrombosis and Vascular Biology suggests that while a diet rich in soy foods may be cardioprotetive, soy isoflavones by themselves will not produce much effect. In this 5 month study, 60 female monkeys whose ovaries had been removed to simulate menopause, were divided into three groups of 20 all of which were fed an atherogenic diet (one which was likely to promote heart disease) with only the source of protein differing among the three groups. One group was given milk-based protein; the second received protein from soy, and the third was fed milk protein supplemented with soy isoflavones.

At the conclusion of the 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.(January 29, 2004)

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 February 2005 issue of 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 annual meeting of the North American Menopause Society, Washington, D.C., October 6-9, 2004. 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 monkeys 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 monkeys at highest risk for heart vessel disease. A low ratio of total cholesterol to HDL (good) cholesterol is considered healthier. In monkeys 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 monkeys 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. He also added, "Studies have shown that heart vessel disease, or atherosclerosis, begins in the 30s and 40s in women. From our work in monkeys, we believe the time to prevent cardiovascular disease in women is before menopause, not after. Soy seems to provide a potent protection in monkeys, in terms of cholesterol levels, which is a good marker for general cardiovascular risk. We presume the benefit would apply to premenopausal women as well."

In the second study, monkeys 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.

In both 12 month long studies, the monkeys were selected to represent women in their 30s and 40s. Half consumed soy with isoflavone levels equal to a human intake of approximately 129 milligrams a day—about twice the amount typically consumed by women in Asia.

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 November 2004 issue of the American Journal of Clinical Nutrition. In this study, which included 1033 pre- and postmenopausal women (361 meat-eaters, 570 vegetarians, and 102 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 .5 grams of soy protein daily.(January 14, 2005)

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.

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 patients (10 men, 4 women) receiving medical care at an educational university hospital and private kidney disease clinic in Tehran. 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.” (December 3, 2003)

Another study, this one conducted at the University of Illinois and published in the August 2004 issue of 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 diabetics prevent kidney disease and improve their cholesterol profile.(Octobe4r 21, 2004)

Colon, Breast and Prostate Cancer Prevention, Plus Relief for Irritable Bowel

The fiber in soybeans also provides preventitive 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. Soybean fiber may also be able to reduce the symptoms of diarrhea or constipation in sufferers of irritable bowel syndrome.

A study published in the January 2004 issue of 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 mice 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 mice 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.” (March 25, 2004)

Colon Cancer-Protective Compound Found in Soy Beans

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 mice 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 mice 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 mice bred to spontaneously develop colon cancer, the rate at which tumors formed dropped 37%.

Soy sphingolipids provided this protection by affecting the expression 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. (June 28, 2004)

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. (Octoer 24, 2003)

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).

In addition to genistein, another isoflavone found in soybeans called daidzen has also demonstrated protective action against prostate cancer. A study published in the July 2003 issue of Cancer Epidemiological Biomarkers that evaluated 398 Chinese men (133 men with prostate cancer and 265 age and residential community matched controls between the ages of 50 and 89) found that those consuming the most tofu had a 42% lower risk of developing prostate cancer compared to those consuming the least. When researchers checked the relationship between the soy isoflavones, genistein and daidzen, which are found not only in tofu, but in soy beans and other foods made from them, those consuming the most genistein were found to have a 47% lower risk for prostate cancer, while those consuming the most daidzen had a 44% lower risk.(September 8, 2003)

Soy foods may also reduce risk of endometrial cancer. Research conducted in Shanghai and published in the May 2004 issue of the British Medical Journal suggests that eating soy foods may be one reason Asian women have the lowest incidence in the world of endometrial cancer (cancer affecting the lining of the uterus).

The study included 832 women with endometrial cancer, aged 30-69 years, and a disease-free, matched control group of 846 women. For 5 years, all subjects answered food frequency questionnaires. When the data was evaluated, a significant inverse association was found between frequency of eating soy foods and endometrial cancer risk. Compared to women who ate the least soy foods, endometrial cancer risk was reduced from 7% to 15% to 33% as soy food intake increased.

Two reasons soy may help prevent endometrial cancer:

Soybeans contain the isoflavones genistein and daidzein, which, although about 1,000 times less potent than human estrogen, can bind to estrogen receptors in the body, blocking out human estrogens and providing a much more gentle estrogenic effect. Plus, minimally processed soy foods are rich in dietary fiber, which has also been shown to lower estrogen levels.(June 30, 2004)

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 July 2004 issue of 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, 179 female monkeys 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 monkeys receiving soy with isoflavones actually had significantly lower levels of estrogen than the monkeys given soy from which the isoflavones had been removed.

“These findings suggest that high dietary levels of soy isoflavones do not increase markers for breast and uterine cancer risk in postmenopausal monkeys and may contribute to an estrogen profile associated with reduced breast cancer risk,” concluded the researchers.

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, while 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. (August 3, 2004)

For Cancer Protection, Eat Whole Soy Foods, Not Purified Soy Products

A study published in the June 2004 issue of Carcinogenesis suggests that not only is the cancer-preventive ability of soy foods markedly reduced in highly purified soy products and supplements, but that such processed foods can stimulate the growth of pre-existing estrogen-dependent breast tumors.

Soy foods contain complex mixtures of bioactive compounds that interact with one another to promote health, while the partially purified isoflavone-containing products consumed in the U.S. may have lost many of the biologically active components in whole soy foods. "These partially purified isoflavone-containing products may not have the same health benefits as whole soy foods," noted William G. Helferich, professor of food science and human nutrition at the University of Illinois at Urbana-Champaign and one of the study's primary authors.

In the study, mice were divided into four groups, one of which received no soy and served as the control group, while the others were given either whole soy flour, soy extract, a mixture of isoflavones, or genistin in pure form. Despite the fact that all groups, except the control group, received an equal amount of the soy isoflavone genistein, "as bioactive compounds were removed, we observed an increase in estrogen-dependent tumor growth," said Helferich.

In the mice given minimally processed soy flour, a form of soy comparable to the whole soy foods consumed in the Asian diet, tumors neither grew nor regressed. But in the mice given dietary soy products containing isoflavones in more purified forms, the tumors grew. "These products are similar to the materials used in isoflavone-containing dietary supplements, which is how many Americans consume these compounds," Helferich noted.

The take-home message for women, especially postmenopausal women with estrogen-responsive breast cancers who are looking for alternatives to HRT: Avoid processed soy products and supplements that contain isoflavones in more purified forms. Choose minimally processed whole soy foods such as endamame, whole soy flour, tofu or tempeh.(June 30, 2004)

A Healthy Transition through Menopause

One of the more popular uses of soybeans lately has been in the treatment of menopausal symptoms. Soybeans contain active compounds called isoflavones that act like very weak estrogens in the body. These phytoestrogens bind to estrogen receptors and may provide enough stimulation to help eliminate some of the uncomfortable symptoms that occur when natural estrogen levels decline. Studies have shown that women who consume soy foods report a significant reduction in the amount of hot flashes that they experience. There is also some evidence that soy foods may even be able to help reduce the bone loss that typically occurs after menopause. And as women's risk for heart disease significantly increases at menopause, soybeans numerous beneficial cardiovascular effects make it a particularly excellent food to consume frequently as menopause approaches. Soyfoods' beneficial effects on menopausal symptoms have recently been studied by Australian researchers at Queensland University of Technology (QUT), who have attempted to translate the dietary and lifestyle patterns of Japanese women, one of which is regularly consuming soyfoods, to their Western menopausal counterparts. The very beneficial results of this research, called The Women's Wellness Program Study, were summarized at the Australasian Menopause Conference held in Hobart, Australia, November 2003.

According to Senior Lecturer in Women’s Health at QUT, Dr. Debra Anderson, “Japanese women are regarded as the healthiest women in the world, averaging a life span at least five years longer than Western women.” The Women’s Wellness Program, a 12-week lifestyle intervention program QUT researchers developed, involved a Westernized Japanese diet rich in calcium and foods high in phytoestrogens, e.g., soyfoods, along with walking and strength exercises.

Study participants, 120 women ranging in age from 50 to 65, were provided a book with lifestyle tips and exercises published by study authors Allen and Unwin, The Menopause Made Simple Program, and encouraged to increase dietary phytoestrogens to 40 mg per day through eating more soy-based foods and grains, raise calcium intake to 1500 mg per day. and drink eight glasses of water daily. Participants were also asked to record their daily diet and exercises in a journal.

Virtually all study subjects experienced significant reductions not only in menopausal symptoms such as hot flushes and palpitations, feelings of depression, fatigue and lack of motivation, but also in body fat, particularly abdominal fat, and blood pressure. Benefits were so significant that, Anderson reported, “Some of the women have ceased hormone replacement therapy, or are considering doing so, and we have encouraged them to discuss this with their GP.”

Next on the research team’s agenda is further studies testing the use of nutrition only and exercise only to see which has the biggest impact. Anderson’s hunch is “that the combination of dietary phytoestrogens is allowing the body to convert the abdominal fat (that women get postmenopausally due to change of hormones) into muscle and the combination of exercise with phytoestrogens is accelerating this very quickly. This is good news for women as abdominal fat is linked very closely to heart disease and is often very hard for women to shift.”(December 3, 2003)

Prevent Hip Fractures in Postmenopause Years

A double-blind, placebo-controlled study involving 203 postmenopausal Chinese women, aged 48 to 62 years old, suggests that soy isoflavones can help women with low bone mineral content prevent hip fractures in postmenopause years. The trial, reported in the October 2003 issue of the Journal of Clinical Endocrinology and Metabolism, randomly divided women into three treatment groups which received daily either a placebo, a medium dose of isoflavones (40 mg isoflavones) or a high isoflavone dose (80 mg isoflavones). All three groups were also given 500 mg of calcium and 125 IU vitamin D daily. At the beginning of the study and one year later, researchers measured bone mineral density (BMD) and bone mineral content (BMC) of the whole body, spine and hip.

Women receiving the high dose of isoflavones had mild, but a significantly higher improvement in BMC at the total hip and trochanter compared to those in the placebo and mid-dose groups, even after adjustments for potential confounding factors. Further analyses revealed that soy isoflavone supplementation was only beneficial among women who started out with average or lower bone mineral content measurements. The researchers concluded, “… soy isoflavones have a mild, but significant, independent effect on the maintenance of hip BMC in postmenopausal women with low initial bone mass,” —in other words, soy isoflavones improve bone density in women who need it, while having little effect on the bones of those whose bone density is already adequate.

The results of this study provide additional support for the findings of a review study published in the September 2003 issue of the American Journal of Clinical Nutrition. In their review, Drs. Kenneth Setchell, one of the foremost researchers in soy’s effects on health, and Eva Lydeking-Olsen examined 17 in vitro studies of cultured bone cells, 24 in vivo animal models for postmenopausal osteoporosis, 15 human observational/epidemiologic studies, and 17 dietary intervention studies. Their conclusions: “the collective data suggest that diets rich in phytoestrogens have bone-sparing effects in the long term, although the magnitude of the effect and the exact mechanism(s) of action are presently elusive or speculative."(December 3, 2003)

Description

The soybean is native to China where it has been cultivated for food for well over 13,000 years. The Chinese name for soybeans means “greater bean,” and this amazing legume could not deserve a more fitting title. After all, what could be greater than a bean that offers such a wealth of nutritional value in addition to its culinary versatility?

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.

The texture of soybeans is so adaptable that they can be processed in a host of different ways making it easy for you to enjoy them in your daily diet. There are fresh soybeans (also known as edamame), dried soybean seeds, soymilk, soynuts, tofu, tempeh, soy flour……the list goes on and on. And with their delicious, slightly nutty flavor and wonderful nutritional profile, this legume known scientifically as Glycine max can offer you max-imum enjoyment and health.

History

Soybeans originated in China over 13,000 years ago where they were considered one of the most important crops in the area. They were introduced into Japan in the 8th century and many centuries later, into other regions of Asia including Thailand, Malaysia, Korea and Vietnam.

Soybeans made their first appearance in the United States in the 18th century, planted by an American who brought them back from China. American farmers began planting soybeans in the 19th century; yet, it was not until the early 20th century, when nutrition pioneers such as George Washington Carver and John Harvey Kellogg began discovering and promoting the health benefits of soybeans, that the “greater bean” began to receive greater public attention. While interest in the nutritional benefits of soybeans has steadily increased since then, in the past few years, a true groundswell of interest has occured. This has come about in response to the recent scientific research that is supporting the numerous ways that soybeans can promote health.

Today, the United States is the world's leading commercial producer of soybeans.

How to Select and Store

How to Enjoy

For some of our favorite recipes, click Recipes.

Tips for Preparing Soybeans:

Before washing dried soybeans, spread them out on a dark colored plate or cooking surface to check for and remove small stones, debris or damaged beans. After this process, place the beans in a strainer and rinse them thoroughly under cool running water.

To shorten their cooking time and make them easier to digest, dried soybeans should be presoaked. There are two basic methods for presoaking. For each, start by placing the beans in a saucepan and adding two to three cups of water per cup of beans.

The first method is to boil the beans for two minutes, take pan off the heat, cover and allow to stand for two hours. The alternative method is to simply soak the beans in water for eight hours or overnight, placing pan in the refrigerator so that the beans will not ferment. Before cooking the beans, regardless of method, drain the soaking liquid and rinse the beans with clean water.

To cook soybeans, you can either cook them on the stovetop or use a pressure cooker. For the stovetop method, add three to four cups of fresh water or broth for each cup of dried beans. The liquid should be about one to two inches above the top of the beans. Bring the beans to a boil and then reduce to a simmer, partially covering the pot. If any foam develops, simply skim it off during the simmering process. Soybeans generally take about three hours to become tender using this method. They can also be cooked in a pressure cooker where they take about an hour to prepare. Regardless of cooking method, do not add any seasonings that are salty or acidic until after the beans have been cooked since adding them earlier will make the beans tough and greatly increase the cooking time.

A Few Quick Serving Ideas:

Replace some of the wheat flour in your favorite baked goods recipe with soybean flour and increase the protein of your cookies, cakes, muffins and breads.

Mix sprouted soybeans into salads or use as toppings for sandwiches.

Frozen edamame is simple to prepare and makes a great snack or appetizer. Just add the soybean pods to slightly salted water and boil for approximately 15 minutes.

Add soybeans to vegetable stews and soups.

Use soymilk in place of cow’s milk as a beverage and cereal topper.

Safety

Allergic Reactions to Soybeans

Although allergic reactions can occur to virtually any food, research studies on food allergy consistently report more problems with some foods than with others. Common symptoms associated with an allergic reaction to food include: chronic gastrointestinal disturbances; frequent infections, e.g. ear infections, bladder infections; bed-wetting; asthma, sinusitis; eczema, skin rash, acne, hives; bursitis, joint pain; fatigue, headache, migraine; hyperactivity, depression, and insomnia.

Individuals who suspect food allergy to be an underlying factor in their health problems may want to avoid commonly allergenic foods. Soybeans are one of the foods most commonly associated with allergic reactions. Other foods commonly associated with allergic reactions include: cow's milk, wheat, shrimp, oranges, eggs, chicken, strawberries, tomato, spinach, peanuts, pork, corn and beef. 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.

Soybeans and Oxalates

Soybeans are among a small number of foods that contain any measurable amount of oxalates, naturally-occurring substances found in plants, animals, and human beings. When oxalates become too concentrated in body fluids, they can crystallize and cause health problems. For this reason, individuals with already existing and untreated kidney or gallbladder problems may want to limit soybean consumption. Oxalates may also interfere with absorption of calcium from the body. For this reason, individuals trying to increase their calcium stores may want to limit soybean consumption, or if taking calcium supplements, may want to eat soybeans 2-3 hours before or after taking their supplements.

Soybeans and Goitrogens

Soybeans contains goitrogens, naturally-occurring substances in certain foods that can interfere with the functioning of the thyroid gland. Individuals with already existing and untreated thyroid problems may want to avoid soybeans for this reason. Cooking may help to inactivate the goitrogenic compounds found in food. However, it is not clear from the research exactly what percent of goitrogenic compounds get inactivated by cooking, or exactly how much risk is involved with the consumption of soybeans by individuals with pre-existing and untreated thyroid problems.

Nutritional Profile

Introduction to Food Rating System Chart

The following chart shows the nutrients for which this food is either an excellent, very good or good source. Next to the nutrient name you will find the following information: the amount of the nutrient that is included in the noted serving of this food; the %Daily Value (DV) that that amount represents (similar to other information presented in the website, this DV is calculated for 25-50 year old healthy woman); the nutrient density rating; and, the food's World's Healthiest Foods Rating. Underneath the chart is a table that summarizes how the ratings were devised. For more detailed information on our Food and Recipe Rating System, please click here.

 

Soybeans, Cooked
1.00 cup
297.56 calories
Nutrient Amount DV
(%)
Nutrient
Density
World's Healthiest
Foods Rating
molybdenum 129.00 mcg 172.0 10.4 excellent
tryptophan 0.37 g 115.6 7.0 excellent
manganese 1.42 mg 71.0 4.3 very good
protein 28.62 g 57.2 3.5 very good
iron 8.84 mg 49.1 3.0 good
phosphorus 421.40 mg 42.1 2.5 good
dietary fiber 10.32 g 41.3 2.5 good
omega 3 fatty acids 1.03 g 41.2 2.5 good
magnesium 147.92 mg 37.0 2.2 good
copper 0.70 mg 35.0 2.1 good
vitamin B2 (riboflavin) 0.49 mg 28.8 1.7 good
potassium 885.80 mg 25.3 1.5 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%

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This page was updated on: 2005-09-02 22:29:14
© 2002 The George Mateljan Foundation