Eating walnuts on a daily basis seems to improve the quality of men's sperm, show study findings.
Men who consumed walnuts each day in addition to their usual diet showed improvements in sperm vitality, motility, and morphology, say Wendie Robbins (University of California, Los Angeles, USA) and team.
The improvements were associated with increases in serum levels of omega-6 fatty acids and the plant source of omega-3 (a-linolenic acid [ALA]), but not with other omega-3 fatty acids, reports the team.
The team's 12-week study of 117 individuals (aged 21-35 years) showed that eating walnuts (75 g/day) in addition to their usual diet significantly increased the men's serum levels of omega-6 and omega-3 fatty acids from baseline, whereas levels remained the same in those who did not add walnuts to their diet.
In addition, the mean change from baseline in sperm vitality was significantly greater in the walnut group, by 5.5%, than in the control group, by 0.5%. Similarly, sperm motility and morphology (normal forms) were also significantly improved, by 5.7% versus 0.53%, and 1.1% versus 0.1.%, respectively.
Further analysis showed that the difference in changes from baseline between the groups were significant for omega-6 and omega-3 fatty acids. However, among the omega-3 fatty acids, the between-group difference was only significant for ALA.
Furthermore, sperm aneuploidy was significantly decreased in the walnut group but not in the control group. And sperm ALA was inversely correlated with the proportion of sperm missing a sex chromosome and the percentage of sperm with any numerical chromosomal abnormality.
Writing in Biology of Reproduction, the researchers say that although food has been linked with reproductive success in women, evidence is somewhat lacking for a link with paternal reproductive fitness. "Evidence is particularly limited for men who routinely consume Western-style diets that may lack optimal nutrients and PUFA [polyunsaturated fatty acids] profiles needed for healthy sperm and fertility," they say.
"These findings are consistent with literature showing a distinct change in FA [fatty acid] profiles during sperm maturation and differentiation that are key to cellular functions such as phagocytosis of residual bodies by Sertoli cells affecting sperm morphology and provision of fluidity to sperm membrane for motility," notes the team.
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