Lycopene – a nutrient found in tomatoes – may boost sperm quality, a study has suggested.
Healthy men who took the equivalent of two tablespoons of (concentrated) tomato puree a day as a supplement were found to have better quality sperm.
Male infertility affects up to half of couples who cannot conceive.
Fertility experts said more studies were needed involving men known to have fertility problems.
NHS advice for men experiencing fertility problems currently suggests they adopt a healthy lifestyle and wear loose-fitting underwear.
It also suggests reducing stress as much as possible and ensuring they have regular sex around the time their partner ovulates to maximise the chances of conception.
But the idea that certain nutrients could boost male fertility has been gaining ground for some time.
Lycopene, like vitamin E and zinc which have been the focus of previous research, is an antioxidant which means it prevents oxidation in cells, and therefore damage.
It has been linked to other health benefits, including reducing the risk of heart disease and some cancers.
The Sheffield team say they used a supplement because lycopene in food can be harder for the body to absorb and so they could be confident each man received the same amount each day.
The men would have needed to eat 2kg of cooked tomatoes each day to get the equivalent dose of lycopene.