Health/Nutrition information
Soyfoods are a source of high-quality protein. In addition, consumption of soy protein provides health benefits that may help prevent or treat certain chronic diseases. Currently, a great deal of research is being conducted to investigate possible health benefits of soy.
Isoflavones
Soyfoods are the richest dietary source of isoflavones. These compounds are being studied intensively because they exert physiological effects that may help reduce risk for certain diseases. Phytochemicals are plant compounds that exert biological effects in the animals or humans who consume them. One type of phytochemical is isoflavones. These are found in varying amounts in legumes, but the only significant source in the human diet is soybeans. Isoflavones are phyto-serms (selective estrogren receptor modulators) and have some estrogen-like qualities, but they are very different from estrogen and have nonhormonal properties as well.
When consumed by animals or humans, isoflavones exert weak estrogen-like effects, but they fall into the same category as tamoxifen. The two primary isoflavones in soybeans are genistein and daidzein, and their glycosides. In fact, most isoflavones occur in soybeans in the form as glycoside (genistein and daidzein). Foods made from soybeans have varying amounts of the isoflavones, depending on how they have been processed.
Soyfoods such as tofu, soymilk, soy flour, and soynuts have isoflavone concentrations of 1.3 to 3.8 mg/g or about 37 to 108 mg per ounce. Concentrations are lower in foods made from a combination of soy and grains. Soy sauce and soybean oil have virtually no isoflavones.
Soy products that are used as additives, such as isolated soy protein and soy protein concentrate, likewise have varying amounts of isoflavones, depending on how they were processed.
Epidemiological studies have indicated that populations that regularly consume soyfoods (as in Asia) have lower incidences of breast, colon, and prostate cancers. The incidence is particularly low for the hormone-dependent cancers. This fact has led researchers to investigate the possible effects of phyto-serms on cancer risk.
Heart Disease
Soybeans have a favorable nutrient profile for heart health, and have other properties that may help lower risk for heart disease. The FDA has authorized the use of health claims about the role of soy protein in reducing the risk of coronary heart disease (CHD) on the labeling of foods containing soy protein. The soy health claim is based on the FDA's determination that 25 grams of soy protein per day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease by reducing blood cholesterol levels. Recent clinical trials have shown that consumption of soy protein compared to other proteins can lower total and LDL-cholesterol levels. Soyfoods are an excellent choice for a heart-healthy diet.
Menopause & Osteoporosis
The hormonal changes that occur during menopause can cause a variety of symptoms and increase risk for heart disease and osteoporosis. Soyfoods, which contain phyto-serms, are being studied for possible efficacy in decreasing the negative effects of menopause.
During peri-menopause, women experience fluctuations in estrogen levels. This can cause uncomfortable symptoms such as hot flashes, night sweats, insomnia, vaginal dryness, or headaches. Changes in estrogen levels have surprisingly wide-ranging effects throughout the body.
Hormone replacement therapy (HRT) is commonly prescribed to help prevent the negative health effects of menopause. However, many women do not want to take HRT because of the possible increased risk for breast cancer. Can soyfoods provide the same kinds of health benefits as HRT, without the risks? Scientists don't have the answer yet, but evidence is accumulating for several health benefits of soy.
Soy contains phyto-serms in the form of the isoflavones, genistein and daidzein. These are known to have estrogen-like qualities, but are very different from estrogen and have nonhormonal properties as well when consumed by animals and humans. Researchers are studying the physiological effects of the isoflavones to find out whether they can serve some of the same functions as physiological estrogens and thereby decrease the health risks associated with menopause. A cross-cultural study of menopause found that women in Japan rarely reported the symptoms of peri-menopause that are common in the West. Post-menopausal Japanese women also have lower rates of osteoporosis and heart disease, and a longer life expectancy.
These facts have fueled an interest in research designed to clarify the relationship between soy consumption and health.
Cancer
Soyfoods fit the dietary guidelines for reducing cancer risk, and they contain anticarcinogens that may prove to be protective. Epidemiological studies show that populations which consume a typical Asian diet have lower incidences of breast, prostate, and colon cancers than those consuming a Western diet. The Asian diet includes mostly plant foods, including legumes, fruits, and vegetables, and is low in fat. The Japanese have the highest consumption of soyfoods.
On the other hand, the typical Western diet includes lesser amounts of legumes, fruits and vegetables, is lower in fiber and complex carbohydrates, and is high in fat. Soyfoods are dietary staples in the Orient but are not commonly included in the Western diet. Japan has a very low incidence of hormone-dependent cancers. The mortality rate from breast and prostate cancers in Japan is about one-fourth that of the United States.
There is evidence that suggests the difference in cancer rates is not due to genetics but rather to diet. Migration studies have shown that when Asians move to the United States and adopt a Western diet, they ultimately have the same cancer incidence as Americans.
The American Cancer Society has created guidelines designed to help reduce the risk for cancer. Their recommendations include: * Choose most of the foods you eat from plant sources; * Limit your intake of high-fat foods.
Soyfoods fit these guidelines for a health-promoting diet. Soybeans contain high-quality protein. Soyfoods and soy products are amazingly versatile and can easily be incorporated into a varied diet.
Allergies
Though uncommon, food allergies can have serious consequences. Only 1 in 3,000 adults is estimated to be allergic to soy protein. This estimate is much lower than is commonly perceived. However, the incidence of true food allergy among adults is quite low, and soy is much less allergenic than are many commonly consumed foods. Also, the reaction to soy protein is typically less severe than is the case for many other foods.
Soyfoods often take the place of the more allergenic foods, such as cow's milk and eggs. However, some people are also allergic to soy. Those who are allergic to soy may be able to tolerate some soyfoods but not others. It is important for these people to read food labels and familiarize themselves with the ingredients.
If a person has a food allergy, alternative foods must be found to provide the missing nutrients. Identifying alternative foods is especially crucial in the case of young children because they are in a phase of rapid growth and development. Soy-based infant formulas have been used for decades to feed infants with cow's milk protein allergies.
Today's soy formulas are equivalent to cow's milk formulas in digestibility, nutrition profile, and acceptability. In healthy infants, soy formulas promote normal growth, nutritional status, and bone mineralization.
Diabetes & Kidney Disease
There is some research evidence that soyfoods may help with blood sugar control in diabetics. It is interesting that the use of soyfoods for diabetes control was one of the first health benefits noted for soy.
Soy may also help lower risk for some of the complications of diabetes, such as kidney disease. Legumes, especially soybeans, have a very low glycemic index and are valuable foods to include in a diabetic diet.
Regardless of source, the total amount of carbohydrate in the diet needs to be within the patient's recommended limit. Blood sugar control may also be improved by choosing carbohydrates that are high in soluble fiber. Some researchers believe that fiber has no measurable benefit unless it is added to the diet in very large amounts.
Supplemental soy fiber may also help by slowing absorption of sugars. In kidney disease, a soy-based diet may be preferable to the traditional low-protein diet for decreasing renal damage. Soy provides high-quality protein without stimulating hyperfiltration and proteinuria. It may also help prevent kidney damage by lowering serum LDL cholesterol levels