Daily Intake of Soya Lowers Sperm Count in Men

Men who have a daily consumption of half a serving of soy food on average may have lower sperm concentrations than men who do not eat soy foods, says a new research.

The same effect was found to be much more pronounced in men who were overweight or obese.

Led by Dr Jorge Chavarro, a research fellow in the department of nutrition at Harvard School of Public Health, Boston, USA, this was the largest study in humans to examine the relationship between semen quality and phytoestrogens (plant compounds that can behave like the hormone, oestrogen).

The researchers found that men who ate the most soy food had 41 million sperm per millilitre less than men who did not consume soy products. (The "normal" sperm concentration for men ranges between 80-120 million/ml).

Soy beans and soy-derived products mainly contain Isoflavones (daidzein, genistein and glycitein), which are plant-derived compounds with oestrogenic effects. The high consumption of isoflavones has been linked with infertility in animals, but so far there has been little evidence of their effect in humans.

After analysing the intake of 15 soy-based foods in 99 men who had attended a fertility clinic with their partners to be evaluated for sub-fertility between 2000 and 2006, the researchers asked them how often and how much they had eaten in the previous three months. The foods included tofu, tempeh, tofu or soy sausages, bacon, burgers and mince, soy milk, cheese, yoghurt and ice cream, and other soy products such as roasted nuts, drinks, powders and energy bars.