Recent decades have seen a dramatic decline in sperm counts among men in industrialized countries. In the US, both female and male factors are found to contribute to infertility in 35% of cases, and a male factor is the only identifiable cause in approximately 8% of cases. Couples who struggle with infertility may seek invasive and expensive procedures to find the root cause(s) of their failure to conceive. Finding ways to support healthy reproductive function naturally may offer an alternative in cases where lower-level interventions may be successful. One nutritional consideration that has support in the scientific literature involves the beneficial application of omega-3 fatty acids. While essential fatty acids, in particular DHA, exhibit positive effects in women, research also highlights the value of omega-3 supplementation for men seeking to support optimal fertility. One such example comes from a recent study whose results suggest that fish oil supplementation may play a role in supporting healthy sperm production.

The study was conducted in Denmark, using young male subjects who reported for compulsory medical evaluations to determine fitness for military service. Among a total of 1679 subjects (age range 18.7-19.4 years), 98 (5.8%) reported having used fish oil supplements during the previous three months. Out of these 98 young men, 53 (54.1%) reported taking fish oil for 60 or more days out of those previous three months. Measurements assessed included semen quality (volume, concentration, and total sperm count), percentage of morphologically normal sperm and motility, plus serum levels of select reproductive hormones: follicle stimulating hormone (FSH), luteinizing hormone (LH), total and free testosterone, and inhibin B levels.

Compared to young men taking no supplements, those who reported supplementing with fish oil had significantly greater semen volume and testis size. There were also slight increases in sperm concentration and percentage of morphologically normal sperm, but these did not reach significance. Men who supplemented had lower FSH and LH, and higher ratios of free testosterone to LH. Changes in inhibin B were not significant. (Inhibin B is believed to be a marker for spermatogenesis.)

Regarding these findings, researchers wrote:

“The association of intake of fish oil supplements with lower FSH levels but not with a difference in inhibin B levels indicates a potential benefit of ω-3 fatty acid on spermatogenic capacity and testicular function. This finding is compatible with our finding of higher sperm count among men with fish oil supplement intake. Thus, fish oil supplement use may be associated with increased FSH sensitivity of the Sertoli cells. Similarly, the lower LH level and higher free testosterone to LH ratio indicate a better Leydig cell capacity in line with a positive association with fish oil supplement intake.”

Overall, the findings support a beneficial role for fish oil supplementation in promoting healthy sperm production and function, which echoes earlier research that found n-3 supplementation results in higher sperm count and enhanced sperm motility and morphology. There appeared to be a dose-response relationship between fish oil intake and total sperm count: 147 million for men with no supplement intake, 159 million for those with supplement intake other than fish oil, 168 million for men supplementing with fish oil on fewer than 60 days, and 184 million for men taking fish oil on 60 or more days. 

Fewer men who’d used fish oil supplements had semen parameters below World Health Organization reference levels compared to men with no supplement intake. Moreover, compared to men with no supplement intake, those who’d taken fish oil on 60 or more days had 0.6mL larger semen volume, 1.5mL larger testis, and a 15% higher free testosterone to LH ratio—a difference researchers noted “should be considered of clinical relevance.”

Compared to men with no supplement intake and after stratification according to supplement intake (only multivitamins, only fish oil, or both), men taking only fish oil had the highest semen volume, cubic root transformed sperm concentration, cubic root transformed total sperm count, and proportion of morphologically normal spermatozoa. Since significant differences were not seen in semen quality or reproductive hormones in men taking other supplements, this decreases the possibility that results could be explained by other nutrients, and also reduces the likelihood of the “healthy user bias”—where those who choose to take nutritional supplements may have an overall healthier lifestyle which would include other factors that may be responsible for the positive impact on testicular function and sperm quality.  

The study does have limitations. Among the most glaring are that no information was gathered with regard to the doses of n-3 fatty acids—neither the total amount nor the specific amounts of EPA and DHA—and that blood or tissue levels of n-3 were not measured. So, the study reported only the frequency of fish oil supplementation but not the dose/concentration, and there are no data regarding associations between n-3 status in the body and sperm quality. 

For men looking for natural ways to support fertility beyond fish oil, another potentially beneficial supplement or dietary factor is lycopene, an antioxidant found in several foods, of which tomatoes are the most recognized. Lycopene is known to support prostate health and recent research indicates lycopene supplementation improves sperm motility and morphology in healthy young men. Zinc is another nutrient that supports healthy testicular function and is crucial for male fertility.

By Amy Berger, MS, CNS