Eating about half a serving a day of soya-based foods could lower a man's sperm count. To look at the relationship between semen quality and a plant form of the female sex hormone oestrogen known as phytoestrogen, which is plentiful in soya-rich foods, researchers from Britain analysed the intake of 15 soya-based foods in 99 men. They were asked how much and how often in the prior three months they had eaten soya-rich foods. The researchers divided the men into groups according to soya consumption levels. Men in the highest group on average ate half a serving per day. It was found that men in the highest intake category had 41 million sperm per milliliter less than men who ate no soya foods. A normal sperm count ranges from 80 million and 120 million per milliliter, and a sperm count of 20 million per milliliter or below is considered low. The association between soya foods and lower sperm count was stronger in overweight men. This was attributed to the presence of higher levels of androgen-produced oestrogen in overweight or obese men. The findings suggest that soya foods could affect the male reproductive system, especially sperm production. However, more studies are needed to check whether soya food could cause infertility.
Human Reproduction
July 2008