Food has been linked with human reproductive success throughout history. Dietary habits and essential nutrients to promote successful reproductive outcomes have been identified for use during the period from before conception. Resent research reveals evidence that men who routinely consume western-style diets lack optimal nutrients and PUFA (polyunsaturated fatty acids) profiles needed for healthy sperm and fertility. Best known sources of dietary PUFAs for persons consuming a Western-style diet include fish and fish oil supplements, flax seed, and tree nuts. Nuts provide a rich source of α-linolenic acid (ALA), a natural plant source of omega-3. Of popular tree nuts, walnuts are particularly rich in ALA, omega-6 fatty acids, anti-oxidants and micronutrients including folic acid. Thus researchers elected to conduct a study based on the use of walnuts and allow the resulting data to speak for itself. “Whether adding walnuts to the diet will go beyond the shifts in sperm parameters, as the study will show, to improving birth outcomes for men within fertility clinic populations or in the general population is not yet known and will require further research.
Young, healthy men who added a daily dose of walnuts to their usual diet had improved semen parameters, a randomized trial showed.
After 12 weeks, those who ate walnuts had better sperm vitality, motility, and morphology compared with those who avoided tree nuts altogether (P≤0.03 for all), according to Wendie Robbins, PhD, of the University of California Los Angeles, and colleagues.
Walnuts also were associated with improvements in serum omega-6 and omega-3 fatty acids, the researchers reported online in Biology of Reproduction.
“Whether adding walnuts to the diet will go beyond the shifts in sperm parameters as seen in this study to improving birth outcomes for men within fertility clinic populations or in the general population is not yet known and will require further research,” they wrote.
In the current study we tested the hypothesis that 75 gm of whole-shelled walnuts/day added to a Western-style diet would beneficially affect semen quality.
The study found that 75gm of walnuts per day added to a Western-style diet improved sperm vitality, motility, and morphology (normal forms) in a group of healthy young men when compared to a control group of men consuming usual diet but avoiding tree nuts. Improved semen quality was associated with increases in blood serum omega-6 FA and in the plant source of omega-3 (ALA) but not with other omega-3s. These findings are consistent with a literature showing a distinct change in FA 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.
Both the Safarinejad RCT with EPA and DHA omega-3 supplements and our RCT that enriched usual diet with ALA omega-3 through eating walnuts found improved sperm motility and morphology (normal forms). In this study, the walnut dietary intervention resulted in a changed serum FA profile for ALA but not EPA and DHA suggesting the beneficial omega-3 effects on sperm from walnuts were related to the plant source of omega-3, ALA. Safarinejad reported changes in sperm DHA and EPA associated with DHA/EPA supplements, however, in our study a significant increase in serum ALA for the walnut group (p=0.0001) was not reflected as a significant change in sperm ALA (p>0.05).
In the case of healthy young men eating walnuts, the intervention improved sperm parameters of vitality, motility, morphology (normal forms), and sperm aneuploidy on a heterogeneous background of semen parameters for men of unproven fertility.
So when it’s said that nuts can improve your nut, what this really means is that walnuts can improve the quality of your sperm.
The study was funded through a grant from the California Walnut Commission and the UCLA Fielding School of Public Health, Center for Occupational and Environmental Health.