There really is no good reason for people to take omega-3 supplements, given they offer only the slightest health benefits on the cardiovascular front but also are associated with a slight increase in prostate cancer among men, Medical News Today reports. Those are the collective findings of a pair of large-scale medical literature reviews of numerous studies examining omega-3 supplementation’s association with cancer and cardiovascular health outcomes.

Omega-3 fatty acids are polyunsaturated fatty acids (PUFAs), which are abundant in nature. Three types of omega-3s play key roles in human health: alpha-linolenic acid (ALA), which is found in plant oils, and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are found primarily in seafood.

The National Institutes of Health stresses that healthy adults in the United States essentially never have an omega-3 deficiency because such fatty acids, especially ALA, are found in a wide range of foods.

In other words, if you eat food, you’re going to be OK.

For one of the literature reviews, which was published in the British Journal of Cancer, researchers analyzed data from 47 randomized controlled trials that included over 100,000 participants. They studied the association between omega-3, omega-6 (another essential fatty acid) and total PUFA intake and the rate of cancer diagnosis.

It turned out that omega-3 and ALA intake had at most a small association with cancer risk. The most notable finding was that such supplementation could result in a small increase in the risk of prostate cancer.

The second review, published in the Cochrane Database of Systematic Reviews, looked at data from 86 trials that included over 160,000 participants. Researchers found that increasing EPA and DHA intake slightly lowered the risk of coronary death and coronary health events in the studies analyzed. However, such findings might not be applicable to the real world, meaning outside of a medical study. The researchers’ conclusion? Increasing EPA and DHA intake has little to no impact on deaths and cardiovascular-related health events and likely has little to no impact on cardiovascular-related death, stroke or heart irregularities.

To put these findings into perspective, the authors of the cancer review explain that if 1,000 males increased their omega-3 intake, it would result in three extra cases of prostate cancer, Medscape reports. Conversely, if 1,000 people increased their omega-3 intake through supplementation, three would avoid death due to coronary heart disease, six would avoid a coronary heart disease event and one would avoid arrhythmia.

Previous research has indicated that omega-3 supplements, including fish oils, do not lower rates of anxiety, depression, stroke, diabetes or death.

To read the Medical News Today article, click here. 

To read the cancer study abstract, click here.

To read the cardiovascular paper abstract, click here.

For related content, see “5 Things That Cause Cancer…and 5 Things That Probably Don’t.”