According to a recent study performed by Harvard University researchers, eating half a serving of soy products per day can lower sperm concentration and may play a role in male infertility problems. This appears to be especially the case for those men who are overweight or suffer from obesity.
The findings of the study were published in a July 2008 press release issued by the European Society for Human Reproduction and Embryology and involved data collected from a group of 99 men attending a fertility clinic.
For the study, men were asked how much and how often they had eaten 15 soy-based foods over the previous three months. The foods included tofu, tempeh, tofu or soy sausages, bacon, burgers, soy milk, cheese, yogurt, ice cream and other soy products like roasted nuts, drinks and energy bars.
"Men in the highest intake group had a mean soy food intake of half a serving per day: in terms of their isoflavone content that is comparable to having one cup of soy milk or one serving of tofu, tempeh or soy burgers every other day"
- Men who ate the most soy food had on average 41 million fewer sperm per ml (milliliter) of semen compared with those who did not consume any soy products. (Normal sperm counts for men range between 80 million and 120 million per ml).
- The relationship between sperm concentrations and soy consumption was greatest among overweight and obese men.
- The link between soy products and sperm concentration was more pronounced in men with originally higher sperm concentrations.
Although the link between soy and sperm count isn't clear, researchers suspect that soy may increase estrogen activity which can negatively affect sperm production and interfere with hormonal signals. Soy beans and other soy-derived products contain a plant compound called isoflavones which has estrogen-like qualities.
This may become further compounded in men who are overweight since fat tissue converts male hormones (androgen) to more female hormones leading to even greater levels of estrogen in the body. Why men who have normal or high sperm counts may be more susceptible to soy products than those with lower sperm counts remains a mystery.
Before giving up on soy, it should be noted that these findings are both preliminary and inconclusive. Additional research and further trials are certainly necessary. You may however wish to consult with your physician if you happen to have a high soy intake and are experiencing abnormal sperm concentrations and/or infertility issues.
Posted by PRS
Wednesday, July 30th, 2008