The soybean is considered very ambiguous in our society. On the one hand, there is great uncertainty regarding the use of genetic engineering in soybean production. On the other hand, soy products are attached to the image of having a particularly great health benefit.
For example, soya is said to have a cancer-preventive effect and alleviate menopausal symptoms. In particular, the isoflavones occurring in the soybean, which belong to the group of phytochemicals, should be responsible for this. Because they exert a similar effect in the body as the estrogens, they are also referred to as phytoestrogens.
Does soy help against menopausal symptoms?
Typical menopausal symptoms are hardly known among traditional Japanese women. However, it is amazing that Japanese women who emigrate to western industrialized countries and adapt to the Western way of life and diet, suddenly suffer from complaints such as hot flashes. Due to the estrogenic activity of isoflavones, they are increasingly being used as an alternative to classical hormone replacement therapy. Thus, for example, phytoestrogen preparations based on soy or red clover extracts are available, which promise relief in menopausal symptoms.
To get to the bottom of this promise, a series of studies examining the effects of phytoestrogen preparations versus placebo (a dummy treatment) were conducted. The results showed no or at least no significant decrease in typical menopausal symptoms in the majority of studies.
Does soy prevent cancer?
It has long been recognized that hormone-dependent cancers, such as breast and prostate cancer, are far less common in Asian countries where soy is part of a traditional diet than in Western industrialized countries. In studies with isolated isoflavones, however, this effect has not yet been demonstrated. There is even evidence that growth in existing cancers could be promoted by the inclusion of high concentrations of isolated isoflavones.
Presumably, besides the consumption of soy products in Asian countries, other lifestyle factors are responsible for the different cancer risks. Possibly the timing of the supply also plays a role. Mammary tumors were found to be rarer in female rats when food rich in isoflavones was given before puberty, but not when fed until adulthood.
Is soya good for the heart?
In addition to the above points, the discussion also includes a reduction in the risk of cardiovascular diseases due to increased consumption of soy products. It is still unclear which ingredients should be responsible for this effect. However, it seems certain that it is not solely due to the content of isoflavones.
Studies have shown that use of intact soy protein but not isolated isoflavones reduces LDL cholesterol (so-called "bad" cholesterol), serum triglycerides and, in some studies, increases HDL cholesterol (so-called "bad cholesterol") "good" cholesterol). Also, a favorable influence on the elasticity of the blood vessels and the fluidity of the blood is attributed to the soybean.
The soybean provides high quality protein, vitamins and minerals. It has a favorable fatty acid composition and contains valuable phytochemicals, the isoflavones. Above all the last mentioned numerous health effects are awarded. This has led to increased availability of isoflavone supplements in the market in recent years.
To date, however, it is not clear whether isolated isoflavones can actually achieve the promised effects. Even opposite effects were reported. The Federal Institute for Risk Assessment (BfR) therefore warns that the long-term use of isoflavone-containing dietary supplements is not without risk, especially for women in and after the menopause. The soybean and products made from it are high quality foods that complement our diet. However, the use of isolated isoflavones still needs critical examination.