Topical Area: Nutritional Epidemiology
Infertility affects ~8-12% of couples worldwide with ~40% attributed to male factors. Recent studies suggest a role for paternal diet in fertility. Walnuts contain a variety of nutrients essential in the development of spermatozoa. We conducted a randomized clinical trial (RCT) to determine if consumption of walnuts improves semen parameters and fertility in men seeking clinical care for male factor infertility.
This was a two arm, single blind, RCT. The comparison groups both received usual care for male factor infertility. One group added 42 gm/d walnuts to their diet, and the other group added a daily nutritional supplement recommended for male reproductive health. Participants (n=75) were enrolled at an infertility clinic located in a large metropolitan medical center. Eligibility was determined by history, physical exam, and lab tests collected as part of clinical care. Research measures included semen analysis and blood sample at baseline and 3 months; ASA24 dietary recall at baseline, 2 and 3 months; and fertility report at 3 months and 1 year.
Age range was 27 to 61 years (39.7 ± 7.0); BMI range 19.6 to 46.9 (26.8 ± 4.5); participant race was Asian 26.2%, White 44.3%, Hispanic White 16.4%, Black 8.2%, other 4.9%. Baseline sperm concentration was 39.4± 30 million per ml; sperm motility 31.1 ± 23.4%; and progressive motility 21.2 ± 15.8%. At 3 months, the walnut group demonstrated increased sperm motility and concentration, p = .04 and p = .07, respectively, whereas no significant changes from baseline were found in the nutritional supplement group. Both groups showed improved sperm morphology, p < .03. Preliminary data from the subset of men with 1-year follow-up data shows higher frequency of pregnancy in the walnut group compared to nutritional supplement, although not statistically significant, p = .09. We continue to follow the remaining participants until their 1-year fertility report.
This RCT demonstrated a beneficial effect of adding walnuts to the diet on sperm motility and morphology in men seeking care for infertility. Preliminary fertility data suggests walnuts may enhance the probability of pregnancy for men with male factor infertility.
Funding Sources :
Center for Occupational and Environmental Health, University of California, Los Angeles; California Walnut Commission