Middle-aged and older men who get enough antioxidants in their diets, through eating foods such as broccoli and tomatoes, may have better-quality sperm than men who don't get as much of the nutrients, according to a US study.
Researchers found that among men aged 45 or older, those who got the most vitamins C and E, folate and zinc tended to have fewer DNA-strand breaks in their sperm, according to a report in the journal Fertility & Sterility.
Strand breaks are a measure of the genetic quality of sperm, which is known to decline as a man ages, though the findings do not prove that antioxidants themselves directly improve sperm quality or boost the chance of a healthy pregnancy.
"People who eat well are probably doing a bunch of other healthy things too," said senior researcher Andrew Wyrobek, of the Lawrence Berkeley National Laboratory in California.
But it wasn't overall nutrition that was linked to older men's sperm quality but the antioxidants specifically, he added in an interview.
This doesn't mean that men should start taking supplements for the sake of their sperm. The men in the study with the best quality sperm just got the recommended amounts, through food or pills.
The study included 80 healthy, non-smoking men between the ages of 22 and 80. They filled out a questionnaire on diet and supplement use, and gave sperm samples.
Among men ages 45 and up, those who got the most vitamin C had 20% less DNA damage than those who took in less of the vitamin. Men in that high-intake group typically got about 700 milligrams of vitamin C a day. The recommended amount for men is 90 mg, but an intake as high as 2,000 mg is considered safe.
The findings were similar with vitamin E, zinc and folate, though the differences in sperm DNA damage were smaller. Again, older men in the high-intake groups typically got more of each nutrient than is recommended, but were still well within the safe ranges.
The recommended daily intake for vitamin E is 15 mg and no more than 1,000 mg, while for zinc it's 11 mg and no more than 40. For folate, it's 400 mg and no more than 1,000 mg.
There was no link between antioxidant intake and sperm quality in younger men.
Wyrobek speculated that in younger men, the body may be under less "oxidative stress," or it may be more efficient at neutralizing that stress.
All of the men in the study were free of fertility problems, and Wyrobek said the findings should not be taken to suggest that downing antioxidants could cure infertility.
Still, Wyrobek said the findings support what's recommended for overall health: getting a nutritious, oxidant-rich diet.
Foods rich in vitamin C include citrus fruits, red and green peppers and tomatoes. Vitamin E is found in certain vegetable oils, nuts such as almost and green vegetables like spinach and broccoli, while zinc sources include seafood, red meat, beans, nuts and dairy.