About 15 percent of all male-female couples run into fertility issues, and up to half the time the man’s reproductive health is the problem. Often, there’s no clear explanation for his low fertility (Ricci et al, 2017).

But it’s clear from looking at other species that chemicals in our environment are a possible cause. Pet dogs, farmed mink, Florida alligators and fish living downstream from wastewater plants are all showing signs of male fertility issues (Ford et al., 2021).

The spread of the typical Western diet, high in carbs and seed oils, appears to be another factor.

Transparent matte red gel capsules of vitamin and oil on gray concrete background
There’s evidence that fish oil supplements can support male reproductive health.

For years, research has found clues that more traditional diets rich in fish and the omega-3 fatty acids they contain are linked to better sperm counts (Salas-Huetos et al., 2017).

On the diet front, there’s now stronger evidence, for the first time drawing from a large pool of men who were not known to have fertility problems. It suggests that fish oil supplements boost a variety of measures of male reproductive health.

What the researchers did

The new work came from a collaboration of Danish and Harvard researchers. The volunteers, 1679 young Danish men, were recruited for a large ongoing study when they showed up to be evaluated for military service. About a hundred of them, close to six percent, said they’d taken fish oil supplements during the past three months.

It turned out that the men who took fish oil had improved markers of reproductive health across the board, including higher sperm counts. They also had more “free testosterone”; that is, a larger percentage of testosterone that is not bound to proteins. That’s positive, as free testosterone boosts fertility.

More than half of this group had taken fish oil for 60 days or more. Their results were better than those for men who had taken fish oil but for fewer days, which strengthens the case that the fish oil was doing the job. When it comes to any intervention – whether its dietary, pharmaceutical or lifestyle - it’s always more convincing to see a dose-dependent relationship (Priskorn et al., 2020). 

Of course, young men taking any kind of supplements are health-minded. Not surprisingly, in this pool they were less likely to smoke and reported better health and physical fitness than men who didn’t take any supplements. So, although the team controlled for age, alcohol intake, smoking, sexually transmitted diseases, diet and other factors, it couldn’t entirely rule out unmeasured factors that might go along with taking fish oil.

Most of the men who took fish oil also took a multivitamin. However, no other supplement alone, including multivitamins, vitamin C, and vitamin D, had any measurable impact.

Because not all the men answered questions about how much fish they ate, this study didn’t control for the whole-fish-consumption factor. In general, the group as a whole and the Danish population don’t eat much fish, the study reported.   

How fish oil boosts sperm

The membrane of a sperm cell is rich in fatty acids, and is important in several steps of fertilization. As sperm matures in its life cycle, the membrane accumulates fatty acids, especially the omega-3 docosahexaenoic acid, or DHA (Lenzi et al., 2000).

Readers of this newsletter know that these fatty acids can’t typically be synthesized in sufficient quantity by the body, but must come from food sources such as seafood or fish oil. The best source of DHA is seafood. Earlier research directly linked a diet rich in fish oil with more DHA in sperm membranes (Safarinejad, 2011) and other work going back more than a decade ties sperm membrane DHA to measures of sperm health: motility, shape and concentration (Jensen et al., 2020). 

Eating fish helps

In a study of 150 male infertility patients at Massachusetts General Hospital, researchers found that men who ate the most fatty dark-flesh fish - including salmon, bluefish and tuna - had a 51 percent higher sperm count than those who ate the least amount of dark-meat fish. Eating white-flesh fish, such as cod or halibut, also appeared to improve fertility.

Chomping down bacon, hot dogs or salami every day appeared to be measurably bad for sperm, but chicken and unprocessed red-meat intake was unrelated.

Man holding wooden box of fresh farm vegetables
Along with plenty of seafood, healthy habits including eating fruit and vegetables and low-fat dairy can boost reproductive health, research shows.

This suggests your best move is to replace processed meats with fish, according to this small study, which found a man could in theory boost his sperm count by an astounding 60 percent (Afeiche et al., 2014).

An overview of research including both men at fertility clinics and other men concluded that diets high in fruit and vegetables with fish or low-fat dairy as the main protein may help boost male fertility (Ricci et al., 2017). A separate overview came to a similar conclusion (Salas-Huetos et al., 2017).

What else can men do to protect or boost their fertility?

Basically, mind the usual rules for good health. Quit smoking, lose extra pounds, don’t overdrink alcohol, and ask your doctor if any medications you take are linked to fertility (Sharma et al., 2013).  

Also, do your best to avoid dangerous chemicals. Though it’s difficult; a new study found that nearly 2,500 chemicals in ordinary items may be toxic (Wiesinger et al., 2021). 

Is this a big problem?

In a word, yes. If epidemiologist Shanna Swan is correct (see her new book, “Countdown”) a man reading this article has half the sperm count, on average, of his grandfather.

If that continues, men won’t be reproducing as of 2060.

The “countdown” is an average drop of one to two percent a year documented between 1973 and 2011. She predicts that most couples will need artificial help by 2045. Also possibly linked to low sperm counts are an increase in miscarriages (Ford et al., 2021).

Bottom line: Before we poison ourselves out of existence with modern “wonders” like chemical pollutants and hyperprocessed food, let’s use that same inventive intelligence to find a way back to the fertile past.

Fish, it appears, can help us get there.   



Afeiche MC, Gaskins AJ, Williams PL, et al. Processed Meat Intake Is Unfavorably and Fish Intake Favorably Associated with Semen Quality Indicators among Men Attending a Fertility Clinic. OUP Academic. https://academic.oup.com/jn/article/144/7/1091/4615605?login=true. Published May 21, 2014.

Ford A, Hutchison G. Male fertility: how everyday chemicals are destroying sperm counts in humans and animals. The Conversation. https://theconversation.com/male-fertility-how-everyday-chemicals-are-destroying-sperm-counts-in-humans-and-animals-158097. Published April 15, 2021.

Jensen, T. K., Priskorn, L., Holmboe, S. A., Nassan, F. L., Andersson, A. M., Dalgård, C., Petersen, J. H., Chavarro, J. E., & Jørgensen, N. Associations of Fish Oil Supplement Use With Testicular Function in Young Men. JAMA network open3(1), e1919462 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6991322/  Published January, 2020.

Lenzi A, Gandini L, Maresca V, et al. Fatty acid composition of spermatozoa and immature germ cells. Mol Hum Reprod. https://pubmed.ncbi.nlm.nih.gov/10694269/ Published March, 2000.

Martínez-Soto JC, Domingo JC, Cordobilla B, et al. Dietary supplementation with docosahexaenoic acid (DHA) improves seminal antioxidant status and decreases sperm DNA fragmentation. Syst Biol Reprod Med. https://pubmed.ncbi.nlm.nih.gov/27792396/ Published January, 2016.

Safarinejad MR. Effect of omega-3 polyunsaturated fatty acid supplementation on semen profile and enzymatic anti-oxidant capacity of seminal plasma in infertile men with idiopathic oligoasthenoteratospermia: a double-blind, placebo-controlled, randomised study. Andrologia.  https://pubmed.ncbi.nlm.nih.gov/21219381/ Published February, 2011.

Ricci E, Al-Beitawi S, Cipriani S, et al. Dietary habits and semen parameters: a systematic narrative review. Wiley Online Library. https://onlinelibrary.wiley.com/doi/full/10.1111/andr.12452. Published December 20, 2017.

Salas-Huetos A, Bulló M, Salas-Salvadó J. Dietary patterns, foods and nutrients in male fertility parameters and fecundability: a systematic review of observational studies. Hum Reprod Update. https://pubmed.ncbi.nlm.nih.gov/28333357/ Published July, 2017.

Siedenburg J. Do we really face a human fertility cliff-edge? Science offers hope. The Conversation. https://theconversation.com/do-we-really-face-a-human-fertility-cliff-edge-science-offers-hope-82022. Published March 18, 2021.

Sharma R, Biedenharn KR, Fedor JM, Agarwal A. Lifestyle factors and reproductive health: taking control of your fertility. Reprod Biol Endocrinol. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3717046/ Published July 16, 2013.

Wiesinger H, Wang Z, Hellweg S, Author. Deep Dive into Plastic Monomers, Additives, and Processing Aids. Environmental Science & Technology. https://pubs.acs.org/doi/10.1021/acs.est.1c00976. Published June 21, 2021.