One hundred and fifty-six men suffering fertility problems had their diet as well as the shape and size of their sperm examined in a Harvard University study.
Researchers found that men who regularly ate processed meat had significantly lower amounts of normal sperm, compared with those who limited the amount of foods like bacon, sausages, hamburgers, ham and mince.
On average, those who ate the equivalent of less than a rasher of bacon a day had 30 per cent more normal sperm than those who ate higher quantities of processed meats. Meanwhile, those who ate a portion of white fish every other day had a similar edge over those who ate fish more rarely.
Dr Myriam Afeiche, from the Department of Nutrition at Harvard School of Public Health, said it was extremely difficult to accurately measure the size and shape of sperm. However, he said advice to eat less processed meat and more fish was good health advice, regardless.