Supplementation of folic acid in the diet may boost the quantity and quality of sperm in men who suffer partial infertility, says a leading toxicologist.

Speaking at the World Life Science Forum in Lyon, Professor Bruce Ames of the University of California said that yet to be published research reveals the importance of folic acid in the diet of men with high sperm counts.

He suggests that folic acid appears able to prevent breaks in the chromosomes, which makes sperm weaker.

The vitamin is recognised as being beneficial for pregnant women as a precaution against birth defects but this is the first time that the substance has been seen to be helpful to male fertility.