Evidence suggests that sperm quality in males over the past 50-70 years has declined, likely due to a combination of dietary and lifestyle factors and exposure to endocrine-disrupting chemicals. For example, diets rich in processed meats, full fat dairy, and sugar-sweetened beverages are associated with poor sperm quality, whereas diets rich in vitamins, minerals, and unsaturated fats improve sperm quality and fertility. Results of a recent observational study demonstrate the effects of fish oil supplementation on sperm quality and testicular function in healthy young males.

Infertility affects 15 percent of couples, with male and female reproductive dysfunction contributing equally to infertility rates. Previous epidemiological research has revealed an association between fish consumption and better sperm quality in males seeking infertility treatment. Fish and fish oil supplements are an excellent source of omega-3 fatty acids, a type of polyunsaturated fat with numerous anti-inflammatory and health-promoting properties. Two previous randomized, controlled trials have reported increased antioxidant capacity and decreased DNA fragmentation in the sperm of males experiencing infertility who were supplemented with omega-3 fatty acids. However, the effects of supplementation in men without infertility is unknown.

The investigators recruited more than 1,600 male participants (average age, 19 years) who presented for a physical examination for military service in the Netherlands. Participants volunteered to provide a blood sample for the measurement of sex hormones and a semen sample. Finally, they answered a questionnaire about health, lifestyle, diet, and dietary supplement use over the previous three months.

Only 5.8 percent of the participants had consumed fish oil supplements in the previous three months and only 3.1 percent consumed fish oil supplements for more than 60 days over the previous three months. Participants who supplemented with fish oil less than 60 days had increased sperm volume and testicle size compared to those who did not supplement. Participants who supplemented for more than 60 days had even greater sperm volume and testicle size. Participants who supplemented with fish oil also had a 20 percent lower concentration of follicle-stimulating hormone and a 16 percent lower concentration of luteinizing hormone, an indication of better testicular cell function and greater capacity for sperm production.

The authors concluded that fish oil supplementation improves testicular function in males without infertility, even after taking into account the intake of other dietary supplements. Because this study did not take dose into account, randomized clinical trials are needed to further examine this relationship.

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