Yellow and orange-coloured fruit and vegetables improve men's fertility, but the carrot produced the best all-round results, a new study reveals.
The sperm-boosting qualities come from chemicals called carotenoids, which give such foods their familiar colour.
These include beta-carotene, which the body can make into the antioxidant vitamin A.
Antioxidants help to neutralise free radicals, destructive groups of atoms made as a by-product of metabolism that can damage cell membranes and DNA.
An international study led by Harvard University in the US found other similar hued foods such as sweet potato and melon can also enhance the quantity and quality of sperm by up to 10 per cent.
It comes amid concern that both the quantity and quality of male sperm appears to be declining in western countries, with some studies showing average sperm counts have fallen by over half.
Estimates suggest around 30 per cent of men in couples seeking IVF treatment are subfertile, and two per cent are 'totally' infertile.
In the latest study almost 200 healthy, young college-age men took part in the tests in which they were given a variety of fruit and veg to see what effect it had on sperm.
Yellow and orange foods helped make the sperm stronger and red fruits, like tomatoes, helped produce fewer "abnormal" swimmers.
But carrots gave men the edge in trying to conceive because they were found to improve sperm performance by between 6.5 and 8 per cent.
Carrots helped sperm "motility" - a term used to describe their ability to swim towards an egg, says a report in the journal Fertility and Sterility.
Carrots have long been prized for their vitamins and fibre, and the proven ability to help improve night vision.
Red fruit and veg, particularly tomatoes which contain the anti-cancer chemical lycopene were associated with fewer abnormally shaped sperm.
They contributed to between 8 and 10 per cent more "normal" sperm, said the research, which could make a significant difference in couples having problems conceiving.
"In a population of healthy young men, carotenoid intake was associated with higher sperm motility and, in the case of lycopene, better sperm morphology," the report said.
"Our data suggest that dietary carotenoids may have a positive impact on semen quality."
A previous study from Harvard shows men eating diets containing most saturated fat had the lowest sperm counts and poorer quality sperm.
However, men who ate more 'good' fats - including omega-3 fatty acids found in fish and some plants - had better quality sperm than those eating less.
- DAILY MAIL