When I Was Young

From TODAY, World, HEAL TH WATCH
Friday July 25, 2008

A diet high in soya may water down those little swimmers and lower fertility: Study

IN THE biggest human study into the effects of soya on fertility, a link between soya-rich diets and lower sperm counts has been detected.

The study, by Dr Jorge Chavarro at Harvard School of Public Health in Boston, showed that men who consumed more than two portions of soya-based foods a week had, on average, 41 million fewer sperm per millilitre of semen than men who had never eaten soya products.

The apparent fall in sperm count is unlikely to make healthy men infertile, but some experts said it could have a significant impact on those already with lower-than-average sperm counts.

A sperm count of between 80 million and 120 million per milliliter is regarded as normal, while men who produce fewer than 20 million sperm per millilitre are regarded as clinically subfertile.

The study builds on previous research in animals and on human tissues that has suggested certain ingredients in soya could harm sperm production.

Male fertility has been in decline in the West for several decades now, with about 20 per cent of young Europeans having a low sperm count, while levels of soya have risen steadily in the Western diet since the 1940s because it is a cheap source of protein.

Soya-based products are now found in two-thirds of manufactured food including biscuits, sweets, pasta and bread, according to the Institute of Food Research in Norwich.

In the study, Dr Chavarro and colleagues at Massachusetts General Hospital recruited 99 men who had visited a fertility clinic between 2000 and 2006.

The men answered a questionnaire which asked them about the amounts of 15 different soya foods they had eaten over the previous three months.

The researchers then put the men into four groups according to the levels of chemicals called isoflavones in their diets.

Isoflavones are ingredients in soya products that mimic the female sex hormone, oestrogen. Each man then provided a sperm sample for testing.

Dr Chavarro found that men who consumed at least half a portion of soya food a day had the lowest sperm counts.

“Our findings suggest that the greater the soya food intake is, the lower the sperm concentration, compared with men who never consume soya food,” said Dr Chavarro.

THE GUARDIA N