Associations of Fish Oil Supplement Use with Testicular Function in Young Men

Abstract

Importance: Many young men have poor semen quality, and the causes are often unknown. Supplement intake of ω-3 polyunsaturated fatty acid has been found to improve semen quality among men with infertility, but the association with semen quality among healthy men is unknown. Objective: To determine if intake of ω-3 fatty acid supplements is associated with testicular function as measured by semen quality and reproductive hormone levels among healthy men. Design, Setting, and Participants: This cross-sectional study included young Danish men from the general population recruited between January 1, 2012, and December 31, 2017, at compulsory examinations to determine their fitness for military service. Young unselected men were approached after the examination and invited to participate in a study of reproductive function, regardless of their fitness for military service. Data analysis was conducted from September 1, 2018, to June 30, 2019. Exposures: Intake of supplements, including fish oil, during the past 3 months. Main Outcomes and Measures: Semen quality, measured as volume, concentration, total sperm count, percentage of morphologically normal spermatozoa, and motility, and serum reproductive hormone levels, measured as follicle-stimulating hormone, luteinizing hormone, testosterone, free testosterone, and inhibin B levels. Results: Among 1679 young Danish men (median [interquartile range] age, 18.9 [18.7-19.4] years) recruited to participate, 98 men (5.8%) reported use of fish oil supplements during the past 3 months, of whom 53 (54.1%) reported intake on 60 or more days. After adjustment and compared with men with no supplement intake, men with fish oil supplement intake on fewer than 60 days had semen volume that was 0.38 (95% CI, -0.03 to 0.80) mL higher, and men with fish oil supplement intake on 60 or more days had semen volume that was 0.64 (95% CI, 0.15 to 1.12) mL higher (P for trend