A fistful of walnuts a day may help keep the fertility doctor away, new research suggests.
Eating 75g of the nuts daily was found to improve the health of sperm in men aged 21 to 35.
Scientists in the US split 117 healthy volunteers into two groups, one of which had walnuts added to their diet.
The nuts are rich in a natural plant source of omega-3, a type of fatty acid thought to be critical to sperm development.
Researchers tested various indicators of the quality of participants' sperm.
At the end of three months, men consuming walnuts had significantly increased levels of omega-6 and omega-3 fatty acids in their blood.
Their sperm also showed improvements in concentration, vitality, motility and morphology (shape). Walnut-eaters also had fewer chromosomal abnormalities in their sperm.