Effect of a phytoestrogen food supplement on reproductive health in normal males

Author: Mitchell JH, Cawood E, Kinniburgh D, Provan A, Collins AR, Irvine DS
Publication: Clin Sci (Lond). 2001 Jun;100(6):613-8

Isoflavones supplements are widely available over-the-counter. There’s some concern because animal studies have shown that the consumption of isoflavones can cause impaired fertility and reproductive tract disorders in some animals. The apparent decline in human sperm quality over recent decades may be related to increased exposure to environmental endocrine disruptors such as phytoestrogens.

The purpose of this study is to determine the effects of a short-term phytoestrogen supplement on semen quality, serum steroids and gonadotrophin levels in human males. Healthy volunteers were given isoflavones supplements: 40 mg daily during a period of 2 months. After respectively 2 and 4 months samples were taken of the blood and semen.

The semen was analysed for volume, sperm count, motility and morphology. The blood samples were analysed for sex hormones, gonadotrophin and isoflavones levels. The isoflavones supplement increased plasma genistein to 1 microM and daidzein concentrations to 0.5 microM. The other parameters (semen quality, sex hormone levels) did not change.

It can be concluded that the consumption of isoflavones supplements at the level of 40 mg daily had no effect on semen quality.