Soy Saponins

Many health benefits of soybeans are attributed to their isoflavones but soy saponins, which are less studied, may also play an important role. Tempeh and other soy products, except soy protein extracted with alcohol, contain high levels of saponins. Raw soybeans contain between 2 and 5 g saponins per 100 g. Saponins are glycosides of steroids, steroid alkaloids or triterpenes found in many plants such as asparagus, soybeans, quinoa, olives, grapes and many herbs including ginseng and soapwort. When dissolved in water they form a stable soapy froth. This can easily be observed when you add water to soybean grits (see pictures above). Because of the presence of both a hydrophilic (sugar) and hydrophobic (steroid) they act as emulsifiers and foaming agents. Soy saponins are divided in 2 groups: group A saponins have and undesirable astringent taste, typical for some soy products, and group B saponins have the health promoting properties. The soybean germ contains most group A saponins, whereas group B saponins are found in the both the soybean germ and cotyledons. The soybean hulls, which are removed during the tempeh production, contain little saponins. Some types of saponins are poisonous but the ones found in soybeans and tempeh are eatable and actually possess health benefits.

Health Benefits of Soy Saponins

Soy saponins may contribute to cholesterol lowering by increasing bile secretion and may reduce the risk of colon cancer.

Cholesterol Reduction - Already in 1979 Potter et al discover the cholesterol lowering property of soy saponins. The ability of saponins to form emulsions or micelles with bile salt in the intestine probably explains their cholesterol lowering activity. Bile salt forms small micelles with cholesterol facilitating its absorption. Because soy saponins bind with bile salt, the absorption of cholesterol is reduced. Some saponins form insoluble complexes with cholesterol, resulting in inhibition of absorption cholesterol.

Anticancer - Scientific studies have illustrated that saponins can lower the risk of colon cancer. Cancer cells also need cholesterol to grow and saponins bind cholesterol rich cancer cell membranes, thereby limiting their growth. A study by Roa et al published in The Journal of Nutrition (1995, 125, 717s-724S) concluded that saponins may help to prevent colon cancer.

Inhibition of HIV - The Japanese study entitled "Inhibitory effect of glycosides like soy saponins on the infectivity of HIV in vitro" and published in AIDS (1989 Oct) concluded that soy saponins, especially saponin B1, may have inhibitory activity against HIV infection. It should be stressed that this was an in-vitro study using cultured cells and that the consumption of soy saponins is not a medicine to cure HIV.

Source : http://www.tempeh.info/health/soy-saponins.php

Health benefits of isoflavones

Research in several areas of healthcare has shown that consumption of isoflavones may play a role in lowering risk for disease. They can fight disease on several fronts. The following potential health benefits are attributed to isoflavones:

• Ease menopause symptoms - The benefits of soy go beyond reducing long-term cancer risk. Recent studies have found that soy isoflavones can reduce menopause symptoms such as hot flushes and increase bone density in women. Indeed, many menopausal and post-menopausal health problems may result from a lack of isoflavones in the typical Western diet. Although study results are not entirely consistent, isoflavones from soy or red clover may be helpful for symptoms of menopause. A study carried out by "Health Test" in 2004 investigated the prescription behaviour of 27 doctors for women with menopause symptoms. It showed that isoflavones were recommended twice (44%) as often as hormonal treatment (22%). The prescribed supplements were mainly based on the following plants: soy, black cohosh and hops.
  
  
• Reduce heart disease risk - Soy isoflavones also appear to reduce cardiovascular disease risk via several distinct mechanisms. Isoflavones inhibit the growth of cells that form artery clogging plaque. These arteries usually form blood clots which can lead to a heart attack. A review of 38 controlled studies on soy and heart disease concluded that soy is definitely effective for improving cholesterol profile. There is some evidence that isoflavones are the active ingredients in soy responsible for improving cholesterol profile.
  
  
• Protect against prostate problems - Isoflavones may be benificial for men's health because they may protect against enlargement of the male prostate gland. Studies show isoflavones slowed prostate cancer growth and caused prostate cancer cells to die. Isoflavones act against cancer cells in a way similar to many common cancer-treating drugs.
  
  
• Isoflavones improve bone health - Soy Isoflavones help in the preservation of the bone substance and fight osteoporosis. This is the reason why people in China and Japan very rarely have osteoporosis, despite their low consumption of dairy products, whereas in Europe and North America the contrary happens. Unlike estrogen, which helps prevent the destruction of bone, evidence suggests that isoflavones may also assist in creating new bone. Other studies are not entirely consistent, but evidence suggests that genistein and other soy isoflavones can help prevent osteoporosis.
  
  
• Reduce cancer risk - Isoflavones seem to be protect agains tumors because thet act against cancer cells in a way similar to many common cancer-treating drugs. Population-based studies show a strong association between consumption of isoflavones and a reduced risk of breast and endometrial cancer. Women who ate the most soy products and other foods rich in isoflavones reduced their risk of endometrial cancer by 54%.

Isoflavones are natural plant hormones

Isoflavones can be found in many foods but the best known source is the soy bean (Glycine max). The soy isoflavones are responsible for most of the soy health benefits. The Soy bean is a plant cultivated as foodstuff whose health properties have recently been discovered. Thorough studies have revealed that the consumption of the soy beans have favourable effects on people's health. Another source of isoflavones is red clover. As opposed to soy beans, red clover is normally not eaten but the isoflavones are extracted in industrial processes and used to make isoflavones supplements.

Isoflavones are natural antioxidants

A recent study has demonstrated that isoflavones have potent antioxidant properties, comparable to that of the well known antioxidant vitamin E. The antioxidant powers of isoflavones can reduce the long-term risk of cancer by preventing free radical damage to DNA. Genistein is the most potent antioxidant among the soy isoflavones, followed by daidzein.

Source : http://www.isoflavones.info/