Soyfoods May Damage Male Fertility

A new study by Harvard University researchers has shown a strong link between consumption of mega amount of soyfood products and lower sperm count in men, especially in obese men.

The study, published in the journal Human Reproduction, suggests that consuming half a serving of soy food a day reduces a man's sperm count, and may play a role in male infertility. The link between the two isn’t clear so far, but scientists think this is perhaps because of the presence of some chemicals, isoflavones, which closely match female hormonesdefine, in nearly all soy-based foods.

"There have been a lot of interest in estrogen and isoflavones in particular and a potential relationship to fertility and other reproductive disorders," said lead researcher Dr. Jorge Chavarro, a research fellow in the department of nutrition at the Harvard School of Public Health.

To reach their findings, Chavarro and fellow researchers collected data on 99 men who attended a fertility clinic for evaluation. The researchers then monitored the soy consumption of the study subjects. They were asked about how much of 15 soy-based foods they ate in the past three months. The soy-based food products included in the study were tofu, tempeh, tofu or soy sausages, bacon, burgers, soy milk, cheese, yogurt, ice cream and other soy products like roasted nuts and energy bars.

After tracking the data, the researchers found that those who consumed the most soy-based foods a week had 41 million fewer sperm per millilitre of semen than men who had never eaten soy food.

"Our findings suggest that the greater the soy food intake, the lower the sperm concentration, compared with men who never consume soy food," said Dr Chavarro.

Although, the evident fall in sperm count is not likely to make healthy men infertile, but some experts think it could have a considerable impact on those already with lower than average sperm counts.

The "normal" sperm concentration for a man is between 80 and 120 million per milliliter. And, the men who produce fewer than 20 million sperm per millilitre are regarded as clinically subfertile.

In addition, Chavarro's team found that the link between soy and sperm concentration was stronger among overweight and obese men. In obese and overweight men, the researchers, though, witnessed a negative effect of soy products on the sperm count, but it was not the direct equivalent of reduced fertility.

Echoing the work of Harvard researchers, infertility expert Dr. Hossein Sadeghi-Nejad, an associate professor of urology at UMDNJ New Jersey Medical School and Hackensack University Medical Center, said that soy may be one factor affecting fertility, especially in men who are either overweight or obese.

"When patients are overweight, the fat tissue converts male hormones to more female hormones," Sadeghi-Nejad said. "So, it is possible that the combination of this estrogenic source [soy] and the extra internal estrogen that is caused by the conversion of androgen to estrogen through the fat has a more deleterious effect in that group of patients."