The soybean is viewed very ambivalently in our society. On the one hand, there is great uncertainty regarding the use of genetic engineering in soy production. On the other hand, soy products have the image of having particularly high health benefits.
Among other things, soy is said to have a cancer-preventing effect and to alleviate menopausal symptoms. The isoflavones found in soybeans, which belong to the group of secondary plant compounds, are said to be responsible for this. Since they exert a similar effect in the body as estrogens, they are also called phytoestrogens.
Does soy help with menopausal symptoms?
Typical menopausal symptoms are hardly known among Japanese women with traditional lifestyles. However, it is surprising that Japanese women who emigrate to Western industrialized countries and adapt to the Western lifestyle and diet suddenly suffer from complaints such as hot flashes. Due to the estrogenic activity of isoflavones, they are also increasingly used in this country as an alternative to classic hormone replacement therapy. For example, phytoestrogen preparations based on soy or red clover extracts are available that promise relief from menopausal symptoms.
To get to the bottom of this promise, a number of studies were conducted to investigate the effect of phytoestrogen preparations in comparison to placebo (dummy drug). In the majority of studies, the results showed no decrease, or at least no significant decrease, in typical menopause symptoms.
Does soy prevent cancer?
It has long been known that hormone-dependent cancers such as breast and prostate cancer occur far less frequently 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 are even indications that the growth of already existing cancers could be promoted by the intake of high concentrations of isolated isoflavones.
Presumably, other lifestyle factors besides the consumption of soy products in Asian countries are responsible for the different cancer risks. It is also possible that the timing of intake plays a role. For example, tumors of the mammary glands occurred less frequently in female rats when an isoflavone-rich diet was given before puberty, but not when fed only in adulthood.
Is soy good for the heart?
Under discussion, in addition to the above, is a reduction in the risk of cardiovascular disease through increased consumption of soy products. It is still unclear which ingredients are supposed to be responsible for this effect. However, it seems certain that it is not solely due to the isoflavone content.
Studies showed that the use of intact soy protein, but not of isolated isoflavones, led to a reduction in LDL cholesterol (so-called “bad” cholesterol), serum triglycerides and, in individual studies, to an increase in HDL cholesterol (so-called “good” cholesterol). Soybeans are also thought to have a beneficial effect on the distensibility of blood vessels and the fluidity of blood.
Conclusion
Soybean provides high-quality protein, vitamins and minerals. It has a favorable fatty acid composition and contains valuable secondary plant compounds, the isoflavones. Especially the latter are said to have numerous health effects. This has led to an increased availability of isoflavone-containing dietary supplements on the market in recent years.
To date, however, it has not been clarified whether isolated isoflavones can actually achieve the promised effects. Even opposite effects have been reported. The German 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 menopause. The soybean and products made from it are high-quality foods that are a good addition to our diet. However, the use of isolated isoflavones still needs critical evaluation.
