For men who find that their required ... contribution, shall we say... to starting a family lacks a little zest, scientists think they've found a possible remedy. And, somewhat appropriately, the secret ingredient is nuts -- walnuts, that is.

In a paper published in the journal Biology of Reproduction on Wednesday, UCLA researcher Wendie Robbins and her team describe how 75 grams of walnuts a day improved the quality of semen in healthy young males in their experiments.

Robbins and her colleagues recruited 117 men that tended to eat a "Western-style diet," meaning lots of red meat and few fish or vegetables. This kind of diet is low in omega-3, a protein involved in sperm development, and previous studies have shown that fish oil, a source of omega-3, can improve sperm performance.

Researchers were curious as to whether a plant-based source of omega-3 would confer similar benefits. They split their subjects into two groups: 59 were given 75 grams of walnuts every day for 12 weeks, and 58 were told to eat normally and avoid consuming tree nuts over 12 weeks.

In the walnut-eating group, "what we saw was an increase in the number of sperm that were viable -- meaning alive in the ejaculate -- plus increased vitality and increased motility. Not only were more sperm able to move, but more were able to move in a linear fashion," Robbins said in a telephone interview.

Men who had weaker-performing sperm saw the most gains from the walnut treatment, Robbins says.

One limitation of the study is that none of the subjects were actively trying to treat infertility problems, but the researchers hope to conduct future experiments to address this.

"We're going to see if we can see the same positive effects in males attending infertility clinics," Robbins says.

Walnuts can confer other benefits to men, Robbins says. They contain the mineral selenium, which plays a role in the production of antioxidants, and the vitamin folate.

And while every expectant or (expecting to be expectant) mother is exhorted to take a medicine cabinet's worth of vitamins and stay at least 25 miles from a sushi restaurant, there isn't as much of the same guidance pounded into would-be father's heads.

"We know exactly what to say to women in terms of 'you should be eating this,' but we haven't spent the same energy on men and their diet," Robbins says.

She points to a crop of studies in animals that suggest that a father's diet impacts not only the health of his children, but that of his grandchildren as well.

"There are things going on with the sperm cell and the message that it carries that can be affecting future generations," Robbins says.

SOURCE: Robbins et al. "Walnuts Improve Semen Quality in Men Consuming a Western-style Diet: Randomized Control Dietary Intervention Trial." Biology of Reproduction published online 15 August 2012.