Center for Occupational and Environmental Health, Fielding School of Public Health, University of California Los Angeles, Los Angeles, CA 90095-1772
School of Nursing, University of California Los Angeles, Los Angeles, CA 90095-6919
David Geffen School of Medicine, Center for Human Nutrition, University of California Los Angeles, Los Angeles, CA 90095-1742
We tested the hypothesis that 75 gm of whole-shelled walnuts/day added to a Western-style diet of healthy young men would beneficially affect semen quality.
A randomized, parallel two-group, dietary intervention trial with single-blind masking of outcome assessors, was conducted with 117 healthy men, age 21 – 35 years, who routinely consumed a Western-style diet. Primary outcome evaluated was improvement from baseline to 12 weeks in conventional semen parameters and sperm aneuploidy. Secondary endpoints included blood serum and sperm fatty acid (FA) profiles, sex hormones, and serum folate.
The group consuming walnuts (n=59) experienced improvement in sperm vitality, motility, and morphology and the group continuing their usual diet but avoiding tree nuts (n=58) saw no change. Comparing differences from baseline between the groups, significance was found for vitality p=0.003, motility p=0.009, and morphology (normal forms) p=0.04. Serum FA profiles improved in the walnut group with increases in omega-6 (p=0.0004) and omega-3 (p=0.0007) but not the control group. Only the plant source of omega-3, alpha-linolenic acid (ALA), increased (p=0.0001). Sperm aneuploidy was inversely correlated with sperm ALA, particularly sex chromosome nullisomy (-0.41, p=0.002). Findings demonstrated that walnuts added to a Western-style diet improved sperm vitality, motility and morphology.
*More research is needed to determine if adding walnuts to the diet will improve birth outcomes for men within fertility clinic populations or in the general population.