What adverse effects do isoflavones have?
Side effects of soy isoflavones
Soy isoflavones or isoflavonoids are plant substances with a chemical structure similar to the female hormone estradiol, found in soybeans, and especially in their fermented derivatives such as tempeh.
In recent decades, supplements with isoflavones have been developed, which have a higher amount and bioavailability of isoflavones than any food with soy.
Does soy have side effects?
Soy has no side effects, but soy isoflavone supplements can have them.
What side or adverse effects can soy isoflavones have?
Supplements with soy isoflavones have a hormonal effect. Although they are sold without a prescription as a food supplement, they are not exempt from contraindications and it is recommended not to take them without medical advice. These precautions are due to the fact that the safety of these supplements is doubtful.
Theoretically, the main adverse effect that can be produced by ingesting an isoflavone overdose is the feminization or appearance of physical traits typically promoted by estrogenic hormones, such as breast augmentation in men (male gynecomastia).
However, only two cases have been described in the medical literature on the subject and these possible effects have not been scientifically proven.
Does soy produce breast augmentation in men?
An article published in 2008 in the medical journal Endocrine Practice reported on a case in which a 60-year-old male patient had developed gynecomastia. The case reported that the person consumed a wide variety and quantity of soy products, specifically soy drink with isoflavones (750ml daily). Upon abandoning the consumption of this product, there was a significant reduction in the size of his breast tissue.
Adverse effects of isoflavones in babies
Exceptionally, in Asia, young children who drink a lot of soybeans can have hormonal imbalances, with the consequent increase in breasts in men. This alteration could be due to the fact that Asian children have a genetics adapted to metabolize soybeans, and therefore their excessive consumption can produce hormonal alterations, temporarily and reversibly.
Until a few years ago, a bottle of soybeans was given to babies with a food allergy to cow’s formula milks. It has been observed that soy bottles greatly increase blood concentrations of these components and, on the other hand, are likely to cause allergy to babies, so they are not recommended.
With current evidence, it can be affirmed that soy does not produce feminization or increase the size of the breasts normally consumed in the western diet.
There is still much to investigate on the effect of isoflavones. At the moment no study is conclusive and therefore it is not recommended to take supplements with isoflavones.
Isoflavone supplements should not be confused with the real and beneficial effects of consuming soy and its derivatives.
More information on isoflavones
9 December, 2019