A study of young California men suggests that eating walnuts may be a simple way to boost male fertility. Men who added 75 grams (about two handfuls) a day of walnuts to their diet showed a significant improvement in their sperms' vitality and mobility.

The substance responsible for walnuts' virile power is alpha-linolenic acid, a fatty acid that the human body is not capable of manufacturing.

The finding could be good news for the roughly 70 million couples worldwide who suffer from infertility or poor fertility. Estimates are that 30-50% of these cases can be attributed to the male partner.

The study looked at 117 healthy California men, age 21-35, all of whom had been eating a typical Western-style diet and none of whom had any known fertility problems. For 12 weeks, half added 75 grams of whole walnuts to their diet. The other half continued eating as they had been, with the one condition that they would avoid eating walnuts or any other tree nut. After 12 weeks, blood and semen samples were taken from both groups and compared.

Not only did the walnut group show improvements in their sperm quality, they also gained no weight and showed no increase in BMI. The further good news is that supplementing a conventional diet with nuts rarely leads to weight gain. Research has found that only a fairly small percentage of the full caloric value of a handful of nuts appears to be metabolized by the body.

Still, it probably makes sense for anyone considering adding nuts to their diet to keep close tabs on their weight. Adding 75 grams a day of walnuts to your diet is adding about 485 extra calories by conventional calorie count, with about 85% of these calories coming from fat.

Other benefits of nut consumption can include lowered cholesterol and decreased risk of metabolic syndrome.

While the current study did not test walnuts on men with known fertility issues, it does suggest that walnuts can help make sperm less sluggish. This is in line with other studies suggesting that championship sperm need championship nutrition.

An article detailing the study was published online by Biology of Reproduction and will also appear in a future print edition of the journal. The study was partially funded by the California Walnut Commission.