LOS ANGELES—Eating about two handfuls of walnuts a day may significantly improve sperm parameters in men and boost their fertility, according to a new study published in the journal Biology of Reproduction. The findings suggest a-linolenic acid, a natural plant source of omega-3 found in walnuts, may be responsible for the improvements.
Researchers at the UCLA School of Nursing conducted the study to investigate the effects of a plant source of omega-3 on sperm. Statistics from the American Society for Reproductive Medicine show that one in six couples is infertile, with about 40% of these cases due to a male factor.
The 12-week study involved 117 men between ages 21 and 35, who were divided into two groups. One group added 75 grams of whole-shelled walnuts to their diet daily; the other group continued their usual diet but avoided eating tree nuts. Both groups ate a typical Western-style diet.
"We found a significant improvement in sperm parameters in the group that consumed the walnuts," said Wendie Robbins, a professor at the UCLA School of Nursing and UCLA's Fielding School of Public Health and lead author of the study. "The men who ate no tree nuts saw no change."
While dietary habits and essential nutrients that promote successful reproductive outcomes for women have been identified, the habits and nutrients that can improve men's reproductive fitness are less clear, the researchers said. In particular, evidence is limited for men who routinely consume Western-style diets that may lack optimal nutrients needed for health, sperm and fertility.