Regular Consumption of Soy Low Sperm Concentrations, Study Finds
The daily consumption of half a serving of soy products reduces sperm concentrations and may affect fertility in men, particularly if they are obese, according to a study published in the journal Human Reproduction.
“There has been much interest in estrogen and isoflavones in particular and their potential relationship to fertility and other reproductive disorders,” said lead researcher Jorge Chavarro, Department of Nutrition at the School of Public Health at Harvard.
Chavarro co-authored the book “The Fertility Diet,” focusing mainly on women, and recommends a specific diet to increase the chances of pregnancy.
In the new study, Chavarro says is not very clear the relationship between soy and sperm count, but speculate that soy increases estrogen activity, a hormone that can have a negative effect on sperm production.
Animal research has shown that isoflavones and estrogen can have a negative effect on reproduction, Chavarro said, adding that there was little evidence of the manner in which these findings apply to humans.
His new research, he said, supports the assumptions of how the results of the animal studies could be applied to humans. Chavarro still believes its findings are preliminary and inconclusive.
“It is too early to say that food should not be used soybean (…) We do not have to worry about whether you are eating too much soya. Not enough information to indicate conclusively that,” he said.
For the study, Chavarro and his colleagues collected data on 99 men who attended for assessment at a fertility clinic. Those men were asked how much they consumed soy foods 15 in the last three months.
The list includes tofu, tempo, tofu or soy sausages, bacon and soy burgers, soy milk, cheese, yogurt, ice cream and other soy products like roasted beans.
Chavarro team found that the men who ate more soy foods had at least 41 million sperm per milliliter of sperm than men who ate no soy.
The standard account of semen is between 80 million and 120 million per milliliter.
In addition the researchers found that the link between soy and sperm concentration was strongest in men who are overweight and obese, as they produce more estrogen than thinner men, and soy may increase those levels even more estrogen, the scientists said
