Consuming fish oil supplements is positively associated with semen volume and total sperm count, larger testicular size, higher calculated free testosterone to luteinizing hormone (LH) ratio, and lower follicle-stimulating hormone and LH levels in young, healthy men, according to results from a study published in JAMA Network Open.
A team of investigators conducted a cross-sectional study in young Danish men to assess whether taking omega-3 fatty acid supplements — including fish oil— was linked to improved testicular function, measured by semen quality and reproductive hormone levels.
A total of 1679 men (median age, 18.9 years) completed the study questionnaire, which assessed vitamin and dietary supplement use within the prior 3 months: 1125 did not use any supplements, 210 used multivitamins, and 98 used fish oil supplements, 53 of whom reported consumption on 60 or more days.
The researchers assessed fasting blood samples from participants to assess reproductive hormone levels and semen samples to examine volume, total sperm count, and sperm motility. No differences in semen quality or reproductive hormones were observed among men who used vitamin C supplements, vitamin D supplements, or multivitamins compared with men who did not take any supplements.
With regard to fish oil supplements, the results differed: compared with men who did not take supplements over the 3-month period, participants who took fish oil supplements fewer than 60 days had a 0.38 mL higher semen volume and men who took fish oil supplements for 60 or more days had a 0.64 mL higher volume (P <.001 for trend).
Trends were similar for testicular size among the different cohorts, with men who took fish oil less than 60 days and men who took fish oil 60 or more days having 0.8 mL larger and 1.5 mL larger testicular size, respectively, compared with men who did not take supplements (P <.007 for trend). Sperm count also increased with increased frequency of use of fish oil supplements.
In addition, men who took fish oil supplements had 20% lower follicle-stimulating hormone levels, 16% lower LH levels, and 8% higher free testosterone to LH ratio compared with men who did not take supplements.
“As we found no clear associations of intake of other supplements with measures of semen quality, we believe that confounding by indication is not likely to explain our findings,” the investigators noted. “However, we did not obtain information about the actual content of [omega]-3 fatty acids in the supplements, and the study was cross-sectional, so we can only claim associations and not causation.”
“To our knowledge, [randomized controlled trials] on intake of fish oil supplements have only been performed among men with infertility, and our findings need to be confirmed in well-designed [studies] among unselected men or in large prospective cohort studies,” the investigators concluded.
Jensen TK, Priskorn L, Holmboe SA, et al. Associations of fish oil supplement use with testicular function in young men. JAMA Netw Open. 2020;3(1):e1919462.