Health benefits of soy have been fairly well established in epidemiological and observational studies. Its wide-ranging benefits include protection from heart disease,obesity,diabetes,high blood pressure,osteoporosis,certain types of cancer and perhaps menopausal symptoms. Yet,not many are aware of how much is beneficial,and many have concerns regarding its safety and recommendations with regard to children.
The protective benefits of soybean arise largely from its plant protein,isoflavones,and a special class of fatty acids known as omega-3 fatty acids.
Research shows that soy protein,when included in a low-fat and low-cholesterol diet,could lower blood total cholesterol and low-density lipoprotein cholesterol (LDL or bad) cholesterol levels,without adversely affecting high-density lipoprotein or good cholesterol levels. In 1999,the US Food and Drug Administration announced that incorporating 25 grams soy protein a day in the diet helps fight coronary heart disease.
Scientists have identified several potential anti-cancer substances in soybeans,isoflavones (phytoestrogens) especially genistein,has caught the attention. Studies have shown that when genistein is added to different types of cancer cells growing in laboratory test tubes,the growth of these cells stops. More than 100 studies have demonstrated the effectiveness of genistein as an anti-cancer substance.
However,there are concerns with regard to certain kinds of cancers which are estrogen-sensitive like breast,colon and prostate cancer i.e. cancers which grow when exposed to estrogen. Soy phyto-estrogens are chemical relatives of the human hormone estrogen and may weakly mimic or oppose the hormones effects. The age at which soy is introduced affects the results. A high soy intake during childhood and adolescence seems to reduce the risk for hormone-related cancers including breast cancer in women before menopause; soy intake by adults may or may not reduce this risk and more research is needed to clarify these relationships.
As for menopause,no consistent findings indicate that soy phyto-estrogens (isoflavones) can eliminate hot flushes. Some evidence does suggest that soy phyto-estrogens may help preserve womens bone density after menopause,but more research is needed to confirm or refute these findings. Awareness of this research has led increasing numbers of consumers to use isoflavone supplements. Phytoestrogen supplements sold as natural hormonal therapy are unproven and may pose health risks. The opposing action of phyto-estrogen should raise a red flag against taking supplements,especially by people who have had cancer or whose close relatives have had cancer. The American Cancer Society recommends that breast cancer survivors and those under treatment for breast cancer should consume only moderate amounts of soy foods and should not intentionally ingest very high levels of soy products. Soy phyto-estrogens may interfere with drugs used in breast cancer treatment. Pregnant women are advised against any unproven soy supplements.
Isoflavones in doses below 2 mg/kg body weight per day through natural foods should be considered safe for most population groups. This accounts for approximately 100 mg of isoflavones and 25gms of soy protein for most. Currently,there is no general formal recommendation for either a minimum or maximum level of isoflavone intake,therefore,there is a need for guidance regarding appropriate isoflavone intake levels.
The dietary guidelines recommend consumption of six servings (three cups) of beans per week for the general population including young adults. A serving is equal to 1/2 cup soaked soybeans,tofu,textured vegetable protein or tempeh,or 1 cup soy milk. This may be a lot of soy,i.e. more than half the daily protein intake should come from soy. As little as one serving of soy,3-4 times a week can still be protective.
Ishi khosla is a former senior nutritionist at Escorts. She heads the Centre of Dietary Counselling and also runs a health food store. She feels that for complete well-being,one should integrate physical,mental and spiritual health. According to her: To be healthy should be the ultimate goal for all.