Soya is one of the oldest and most nutritious foods in the world. In the 11th century BC it was primarily consumed in Northern China, spreading to the west and the U.S.A. in the middle of the 18th century and only more recently to Europe. Soya is mainly used in industry and for animal feed despite the fact that it is the third most important crop world-wide today and less than 3% is consumed by humans.
What has most interested scientists in recent years is the discovery of phytochemicals and the profound benefits of Soya on human health. Soya has many nutritional advantages as it contains protein, fibre and isoflavones which have positive effects on cholesterol, bone density, menstrual and menopausal symptoms as well as preventing certain cancers. It is thought to be a wonder food by the Chinese who believe it can cure kidney disease, water retention, common colds, anaemia and leg ulcers.
In China, the soya bean has been cultivated and used in different ways for thousands of years. Soya was considered as one of the 5 holy crops, besides rice, wheat, barley and millet.
Soya beans contain high amounts of protein, including all essential amino acids (the only such vegetable source). Soya beans are also a rich source of calcium, iron, zinc, phosphorus, magnesium, B-vitamins,omega 3 fatty acids andfiber.
The cholesterol lowering effect of Soya milk and its role of heart disease was widely recognized in the mid 90s when the results of a meta-analysis of 38 clinical studies were published. The results demonstrated that a diet with significant Soya protein reduces Total Cholesterol, LDL cholesterol (the "Bad" cholesterol) and Triglycerides.
The average consumption in these studies was 47 grams per day of Soya protein, which is a considerable amount. One way to include this is to try a Soya protein beverage or powder that may add 20 grams preserving. Soya protein was effective even in people who were already following the American Heart Association's 30 percent-fat diet. Soya protein appears to lower triglyceride levels while preserving HDL cholesterol.
Researchers Erdman & Potter in 1993 reported in the American Journal of Clinical Nutrition a 12 percent drop in cholesterol when 20 to 25 grams of Soya protein and fiber were included in the diet. Soya beans contain soluble fiber, which is known to interfere with the absorption and metabolism of cholesterol.
As a result of these findings, in 1999, FDA authorized a health claim about the relationship between Soya protein and Coronary Heart Disease (CHD) on labelling of foods containing Soya protein.
A heart health claim can be found on qualified Soya products.Health Claim:
Diets low in saturated fat and cholesterol that include 25 grams of Soya protein a day may reduce the risk of heart disease. One serving of [name of produce] provides [amount]g of Soya protein.
A few recent studies released in 2005 found that Soya only had a modest effect on cholesterol levels. The American Heart Associationno longer recommends Soya for heart disease. FDA is currently reviewing its policy on Soya health claim. So what should you do? Enjoy your Soya foods like before. It may not lower cholesterol to an extent we originally thought, but it certainly does not harm our health!
Many Soya foods are naturally high in calcium (some fortified with calcium because it is a good source of a particular coagulating agent). In addition, Soya also contains magnesium and boron, which are important co-factors of calcium for bone health.
Isoflavones in Soya foods may inhibit the breakdown of bones. Daidzein, a type of isoflavone, is actually very similar to the drug ipriflavone, which is used throughout Europe and Asia to treat osteoporosis. One compelling study completed by Erdman in 1993 focused on post-menopausal women who consumed 40 grams of isolated Soya protein daily for 6 months. Researchers found that these subjects significantly increased bone mineral density as compared to the controls.
Another study published in the Archives of Internal Medicine in September 2005 also found that intake of Soya food was associated with a significantly lower risk of fracture, particularly among early post-menopausal women.
Alleviating menopausal symptoms
In Japan, where Soya foods are commonly consumed daily, women are only one-third as likely to report menopausal symptoms as in the United States or Canada. In fact, there is no word in the Japanese language for "hot flashes".
Current studies showed that Soya only helps some women alleviate menopausal symptoms. Indeed, Soya is more effective in preventing than alleviating hot flashes. Despite these findings, the North American Menopause Society in 2000 recommended that 40 - 80mg of isoflavones daily may help relieve menopausal symptoms.
Among all cancers, data on Soya and prostate cancer seems to be the most promising; many studies support its role in the prevention and possible treatment of prostate cancer.
While some studies showed Soya offers a protective effect against breast cancer, a few studies showed the estrogen-like effects in isoflavones may be harmful for women with breast cancer. American Institute for Cancer Research stresses that data on Soya and breast cancer are not conclusive, and more work is needed to be done before any dietary recommendations can be made.
What we know at this point is the phytoestrogens in Soya foods are "anti-estrogens". In other words, they may block estrogen from reaching the receptors - therefore potentially protecting women from developing breast cancer. Studies found that pre-menopausal women may benefit from eating Soya foods as their natural estrogen levels are high.
However, this may not be true to post-menopausal women. Studies found that Soya could become "pro-estrogen" in women with low levels of natural estrogen. In other words, concentrated Soya supplements may add estrogen to the body and hence increase breast cancer risk in post-menopausal women. Therefore, post-menopausal women should avoid taking concentrated Soya supplements until more is known. Eating Soya products, however, is not harmful.
Soya beans are very versatile: soya beans can be used as whole soya beans, soya sprouts, or processed as soya milk (Calcium-fortified Soya milk), soya nuts, edamame, tofu, tempeh, soya sauce or miso. Other products such as Soya patties, Soya cheese, Soya yogurt and breakfast cereal.
Although it is still inconclusive that Soya can prevent any diseases, many studies have shown promising results. Include Soya products in your diet and enjoy the possible health benefits they may bring.
With increasing public concerns regarding genetically modified foods, look for Soya products which use non-genetically modified Soya crops in their production.
Soya is also used as ingredient for non-food products, such as candle wax and biodiesel. Soy candles are becoming more popular because they burn longer and healthier.
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