Soya not the cause of low sperm counts

The Soya Protein Association refutes your article (Soya-based foods may harm male fertility, say scientists, July 24). The study on which this article is based is incomplete and does not tell the full story. In the study by Dr Jorge Chavarro from the Harvard School of Public Health all participants presented themselves for semen evaluation. The estimate of the participants' soya foods intake was only based on a questionnaire of their recall of their previous soya foods consumption.

The study did not determine what other factors such as foods, medications, sexual activities or environmental factors may have directly affected the drop in sperm count. The study also did not find a negative relationship between soya and sperm mobility or sperm quality, both of which are key factors to fertility.

Several studies have been conducted into soya and fertility, including a study undertaken in 2001, where healthy young men where supplemented with soya during a two-month period. Ejaculated volume, sperm concentration, count and motility of sperm cells were not affected. No soya study with humans has ever shown a negative relationship between soya and sperm mobility and quality.

Generations of Asians have regularly consumed soya without fertility disorders, and Asian countries have prodigiously produced very healthy, highly functioning children for centuries.

Obesity may be the explanation. Dr Chavarro found that high soya food intakes are associated with lower sperm concentration but "the association was more pronounced among overweight men". Men with high levels of body fat are likely to produce more oestrogen.

Many other human clinical studies have shown that soya can lower cholesterol, may boost cognitive function and may protect against prostate cancer.
Nigel Duffin
Chair, Soya Protein Association