Soy are rich in protein, oil, carbohydrates, vitamins, minerals and fiber. They have been grown in China for at least 5000 years, mainly in the northern and north-eastern part of the country. The soya bean became a staple of the Chinese people diet and continues to be used in many forms including soya milk, tofu, soy sauce, bean sprouts, soy oil, soy flour and so on. They can also be dried to prolong their nutritional value.

The ideal level of cholesterol is 180 milligrams or less, per 10 milliliters of blood. Chances of getting coronary heart disease and stroke increase with cholesterol level that exceeds this. Since soy protein can effectively reduce the cholesterol level, a soy protein diet can help prevent these conditions. According to Dr. James Anderson, even a 10 to 15% reduction in blood cholesterol level can result in a 20 to 30% reduction in the risk of coronary heart disease.

Animal studies suggest that soy/isoflavones inhibit the development of breast and prostate tumors. These studies are consistent with the low rates of breast and prostate cancer in Asian countries. (Source: Dr. Mark Messina at the Talk on " Health Benefits of Soya Beans", July 10, 1999, Hong Kong)

The University of Kentucky metabolism research team, headed by James Anderson, M.D. reported in the August 3, 1995 issue of The New England Journal of Medicine that after a review of 38 clinical studies, it was found that soy can effectively reduce the cholesterol level. In this research, an average of 47 gram of animal protein intake was substituted by soy protein daily. After just one month, it was found that the cholesterol level had been reduced by 23 milligrams per 100 milliliters of blood. This equals approximately 9% of the body's total cholesterol. For those who had a high cholesterol level at the beginning of the testing, the reduction was even more significant at about 20%. The most important finding was that only the low-density lipoprotein (LDL) cholesterol or "bad cholesterol", which contributes to atheroclerosis, was reduced. The high-density lipoprotein (HDL) cholesterol or "good cholesterol" which protects against heart disease was unaffected.

Health Benefits of Soybeans

" Presented by Dr. Mark Messina at the Talk on "The Cow of China", Oct 18, 2003."

Introduction

Soyfoods provide excellent nutrition, they are low in saturated fat and without cholesterol and the quality of soy protein is equal to the quality of animal protein. Recognition of the high quality of soy protein led the U.S. Department of Agriculture in 2000 to allow soy protein to replace 100% of the animal protein in the National School Lunch Program.

Soybeans contain a number of biologically active components but unquestionable it is the isoflavones that have received the most attention and which are most often implicated as the constituents responsible for the hypothesized health benefits of soyfoods. Isoflavones are quite different from estrogen and have a variety of non-hormonal properties that are especially relevant to cancer prevention and treatment.

Coronary Heart Disease

The cholesterol lowering effects of soy protein were first demonstrated in humans in 1967. In 1999, the U.S. Food and Drug Administration (FDA) approved a health claim for soy protein for cholesterol reduction and in the following year the American Heart Association endorsed the use of soyfoods for people with elevated cholesterol. In 2002, the United Kingdom approved its version of a health claim for soy protein under the Joint Health Claims Initiative (JHCI).

Soy protein may also be hypotensive as a recent review found that two-thirds of the better designed trials reported decreases in blood pressure. Lowering systolic blood pressure from just 2 - 5 mmHg has been estimated to reduce stroke and CHD risk by 6-14% and 4-9%, respectively. Furthermore, isoflavones may have independent coronary benefits. For example, isoflavones have been shown to increase the flexibility of the large arteries, and isoflavone-rich soy protein may enhance arterial reactivity and inhibit LDL-cholesterol oxidation.

Breast Cancer

Early life factors are thought to play in the etiology of breast cancer. For example, breast feeding, parity, and early pregnancy, are thought to reduce risk of breast cancer. There is an exciting and intriguing hypothesis that has both animal and epidemiologic support is that early soy intake is also one of these early life protective influences.

Consistent with the animal studies in the United States are the results from two case control studies, one conducted in Shanghai and the other in the United States that involved women of Asian ethnicity. In the former study, soy consumption (11 g soy protein/day) during the teenage years reduced risk of developing breast cancer by 50%. Soy consumption during adulthood had no bearing on these findings. In the latter study, soy consumption throughout life reduced risk by 35% whereas soy consumption only during adulthood was not protective.

Initial interest in the role that soy might have in reducing breast cancer risk was based on three early observations: (1) low breast cancer rates in Asia; (2) animal research showing adding soybeans to the diets of rats inhibited mammary cancer; and (3) data showing that weak estrogen-like compounds such as isoflavones can exert antiestrogenic effects under some experimental conditions. It is also widely recognized that isoflavones have potentially important non-hormonal effects relevant to cancer prevention and treatment.

Osteoporosis

The skeletal effects of both soy protein and the soybean isoflavones are being investigated. Numerous short-term clinical trials dating back to the 1980s have shown that soy protein decreases urinary calcium excretion when replacing animal protein. This advantage of soy protein is quite attractive considering most women do not meet dietary calcium requirements. Various studies have also suggested that isoflavones may inhibit bone loss in much the same way that estrogen does.

Menopausal symptoms

Messina and Hughes recently reviewed 19 trials involving over 1700 women that examined the effects of soyfoods and isoflavone supplements on menopausal symptoms. Six trials were excluded from their analysis, two involving breast cancer patients, two which reported data on severity but not hot flush frequency, one that was not blinded, and one that did not include a control group. They found among the remaining 13 trials that there was a statistically significant relationship between initial hot flush frequency and treatment efficacy. More specifically, the correlation indicates that hot flush frequency will decrease about 5% (above placebo or control effects) for every additional initial hot flush/day in women whose initial hot flush frequency is 35/day.

Thus, soy and isoflavones have modest beneficial effects but only in women with frequent hot flushes. In practical terms this means that in theory a women with eight hot

flushes per day who experienced a typical placebo response of 25% would experience a 40% improvement by consuming soy or isoflavones; thus, hot flushes would decrease from eight per day to 4-5 per day.

Cognitive Function

Dementia rates in East Asia where soyfoods are consumed, are lower than those in Europe and rates of dementia and AD are reportedly higher among Japanese men living in Hawaii compared to native Japanese in Japan. Additionally, maintaining a more Japanese lifestyle is associated with better cognitive function among Japanese women living in the West.

Three clinical trials have found isoflavones enhance some aspects of cognition and memory.

Prostate Cancer

Worldwide, cancer of the prostate is the fourth most common cancer and sixth most common cause of cancer death in men. There are striking differences in prostate cancer rates among regions in the world, however. Compared to Western rates, prostate cancer incidence and mortality in China and Japan is extremely low; in fact, they are as low as the breast cancer rates in those countries. The low rates in soyfood consuming countries provided initial motivation for investigating the impact of soy intake on prostate cancer risk.

In vitro, the main soybean isoflavone genistein inhibits the growth of testosterone-dependent and independent prostate cancer cells. It also reduces the ability of prostate cancer cells to metastasize independent of cell growth inhibition. In addition, in a dose-dependent manner genistein decreases the growth of human-patient benign prostatic hypertrophy tissue and prostate tumors in histoculture. Although the epidemiologic literature is limited, studies in Hawaii, California, and China, have recently found soy intake to be associated with a reduced risk of prostate cancer.