If you aspire
to fatherhood, it might not hurt to go a little nuts. Walnuts, that is.
Eating 2.5
ounces of walnuts a day -- a little more than half a cup -- for 12 weeks
improved sperm quality in healthy young men, researchers report. Their study is
part of a growing body of evidence that men’s dietary and lifestyle choices
might affect their fertility.
The new
study, funded in part by the California Walnut Commission, enrolled 117 men
aged 21 to 35 who ate a typical Western diet. Half the men were randomly
assigned to eat 2.5 ounces of walnuts a day, along with their usual diet. The
other men were told to continue their regular diet but not to eat any tree
nuts.
Walnuts are
the only nuts with appreciable levels of omega-3 fatty acids, which some
studies of male infertility have linked to better sperm quality, says
researcher Wendie Robbins, PhD, of the UCLA Fielding School of Public Health.
Animal and human studies have shown that omega-3 fats and other polyunsaturated
fatty acids “play critical roles in sperm maturation and membrane function,”
Robbins’ team writes.
Previous
research has shown that men with poor sperm counts saw improvement after taking
fish oil supplements high in omega-3 fats, Robbins says. And a study of men
attending a fertility clinic, published in May by the journal Human
Reproduction, found that high intake of omega-3 fats was linked to more
normal sperm size and shape, while high intake of saturated fats was related to
lower sperm concentration.
In the new
study, most of the walnut eaters snacked on the shelled whole nuts straight out
of the package, Robbins says. Others mixed them with applesauce and cinnamon in
a blender or chopped them up and added them to meatloaf, hamburger, and
spaghetti sauce. Before and after the experiment, the men’s semen quality was
analyzed by a researcher who did not know which ones had eaten walnuts. The
researcher looked at sperm concentration, vitality, ability to move, shape and
size, and chromosome abnormalities, all thought to be related to fertility.
Walnuts and
Sperm Quality
At the end of
the 12-week study, sperm quality improved only in the men in the walnut group.
And the walnut eaters whose sperm were the worst swimmers at the beginning of
the study saw the biggest improvement at the end, Robbins says.
In up to half
of couples having difficulty getting pregnant, at least part of the problem is
related to male reproductive issues, according to the American Urological
Association. Whether adding walnuts to the diet will improve men’s chances of
fathering children remains to be seen, but it couldn’t hurt, says Robbins, who
next plans to study walnuts’ effect on the sperm of men with reproductive
issues.
“I would say
that it’s time that we pay more attention to what the male eats around the time
of conception,” Robbins says. Robbins’ study appears online in the journal Biology
of Reproduction. "I think this highlights how important dietary
factors are in promoting fertility health," says John Petrozza, MD,
director of the Massachusetts General Hospital Fertility Center. He
was not involved with the study.
What has yet
to be determined is the optimal amount of walnuts for improving sperm quality,
he says. "This will come out with future papers. For now, the idea is to
eat healthy with a varied diet."
WebMD
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