US scientists have found a possible link between low dietary folate levels and abnormal sperm in men. The findings, from the University of California (UC), Berkley, and the Lawrence Berkley National Laboratory, provide further evidence that healthy diets aid fertility.
Folate is a soluble B vitamin found naturally in foods such as citrus fruits, green leafy vegetables and pulses. The synthetic form, folic acid, can be taken in dietary supplements. The benefits for women of high folate levels are well established in preventing birth defects, but this is the first time a reproductive benefit for men has been shown. The normal recommended daily allowance (RDA) of folate for humans is 200 micrograms, and 400 micrograms for women trying to conceive and during pregnancy.
The study, published in the journal Human Reproduction, looked at samples from 89 healthy, non-smoking men aged between 22 and 80, and information about their diet and supplementary intake. They found that men who ingested high levels of folate - between 722 and 1150 micrograms per day - had 20-30 per cent lower levels of abnormal sperm than men with low folate intake.
The researchers were looking at forms of 'aneuploidy' in the sperm. Aneuploidy is an abnormal number of chromosomes in cells. If these abnormal sperm fertilise an egg, the resulting fetus can have the wrong number of chromosomes, something that can lead to chromosomal disorders such as Down's syndrome. Other risk factors also include miscarriage during pregnancy. The researchers targeted specific chromosomes - chromosomes 21, X chromosome and Y chromosome - as these are associated with the common types of aneuploidy in live births.
Brenda Eskenazi, professor of epidemiology and maternal and child health at UC Berkeley's School of Public Health, was the co-principal investigator of the study. She says: 'in previous studies, we and others have shown that paternal micronutrient intake may contribute to successful conceptions by improving the quality of the sperm. This study is the first to suggest that paternal diet may play a role after conception in the development of healthy offspring'.
The scientists warn that this is not conclusive evidence yet, and both men and women should take a serious look at their diet and lifestyle when trying to conceive. Smoking, drinking excessively and unbalanced diets are highly likely to affect fertility.
In the US, folic acid has been added to breads, flour, cereals and other grain products since 1998 to ensure women get their RDA of folate. A decision on whether folic acid should be added to bread and flour in the UK is due next year.