02 April 2007
ByAppeared in BioNews 401
Recent research published in the journal Human Reproduction found that men whose mothers had eaten a lot of beef during pregnancy were three times more likely to have a sperm count so low that they could be classed as sub-fertile.
The study, carried out at the University of Rochester Medical Centre in New York, US, aimed to examine the relationship between semen quality and the long-term effects of growth hormones and other chemicals used in the production of beef.
In 1988, Europe banned the beef industry from using growth-promoting chemicals to increase yield, but while some growth promoters were banned in the US, others, such as the sex hormones testosterone and progesterone, are still in use.
The study focused on data from partners of 387 pregnant women in five US cities between 2000 and 2005, and on the mothers of the fathers-to-be. Of the 51 men whose mothers remembered eating the most beef, 18 per cent had sperm counts classified by the World Health Organisation as sub-fertile. However, while the study revealed a significant link between the lowest sperm counts and mothers who were the highest beef consumers (seven or more beef meals per week), researchers could not pinpoint hormones, pesticides or other environmental chemicals as a direct cause.
'What we are really doing here is raising an issue', said Shanna Swan, director of the Centre for Reproductive Epidemiology at the University of Rochester and lead author of the study. 'The average sperm concentration of the men in our study went down as their mothers' beef consumption went up. But this needs to be followed carefully before we can draw any conclusions'.
All 387 men in the study were able to conceive a child, so although sperm counts were low in some cases, none of the men were actually infertile. However, there is some concern that high beef consumption by pregnant women may alter sperm production of the male fetus in utero, particularly at the end of the first trimester during the critical period for testicular development. Swan pointed out that several explanations for the findings were possible, such as pesticides and other contaminants in cattle feed, as well as lifestyle factors during pregnancy that may correlate with greater beef consumption.