Birgit Reitz-hofmann
About 75 grams a day -- 2.6 ounces -- of walnuts a day provide healthful omega-3 fatty acids, vitamins such as folic acid and minerals important for sperm development such as zinc and selenium.
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NBC News
updated 8/17/2012 8:47:43 AM ET 2012-08-17T12:47:43

A couple of handfuls of walnuts a day can make a man’s sperm stronger, faster and prettier, researchers said -- and it’s possible the nuts could provide a natural solution for some men with fertility problems.

Tests on healthy, young men -- none of whom were infertile -- showed walnuts perked up their sperm considerably. Dr. Wendie Robbins and UCLA researchers want to test men with fertility problems next.

The nuts provide healthful omega-3 fatty acids, vitamins such as folic acid and minerals important for sperm development such as zinc and selenium, Robbins says.

“I don’t think we have paid enough attention to young men and their diet when they are ready to start a family,” Robbins said. “It’s all about the woman. There is not a lot that we know to tell men. This was really fun.”

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For the study published Thursday, the researchers recruited 117 healthy men, ages 21 to 35, who were eating normal Western diets. Half the men, 58 in all, got a batch of snack-sized packs of walnuts to eat every day on top of their normal diets, while the others just continued normally. The researchers tested their sperm at the beginning and after three months.

“The men who were eating the walnuts had more sperm that had normal shapes compared to men just on the regular diets,” Robbins says.

The dose of walnuts was important. Robbins settled on 75 grams a day -- about 2.6 ounces -- an amount that was shown to raise blood levels of omega-3 fatty acids, to lower cholesterol and, most importantly, not put weight on the men. “These were healthy, fit young men and they were concerned about their figures,” Robbins said.

This amount was equal to two and a half one-ounce snack packs of walnuts a day.

“We also gave them recipes,” Robbins said. The men were told they could sprinkle the nuts on cereal, salad or yogurt.

About 20 percent of the men had low sperm counts, although they hadn’t been diagnosed as infertile. The sperm of these men, it turned out, improved the most after eating walnuts every day for three months, Robbins reported in the journal Biology of Reproduction.

At least one study, done in Iran, showed that men who took fish oil supplements after visiting an infertility clinic had improved sperm quality. But Robbins didn’t want to use fish oil, even though it’s rich in omega-3s. And some people don't want to take a supplement.

"We wanted to look at a plant source of omega-3," she said. "Walnuts are a renewable resource, a little more than, say, fish. We are fishing out a lot of places."

Now Robbins wants to test the idea in men with fertility problems. She noted some studies that had raised fears that the sperm count of men living in Western societies was going down, although researchers do not agree on whether this is actually happening. “Some people suggested this could be due to the Western diet,” she said. “Diet is really powerful and much underrated.”

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