Are Fish Oil Supplements Too Good To Be True? Here's What a New Study Found

A recent cohort study looked at the long-term effects of regular use of the supplements and its association with cardiovascular disease.

Vitamins and supplements, close-up
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Fish oil supplements are a daily staple for millions of Americans, with the US market for them currently worth billions of dollars. These products are high in omega-3 fatty acids, which the body needs for muscle activity and cell growth. Some research has also suggested these dietary supplements could prevent cardiovascular disease. But a recent cohort study looked at the long-term effects of regular use of the supplements and its association with cardiovascular disease. The results suggest it could increase the risk of first time heart disease, at least among those who have good heart health.

The study, published Tuesday in BMJ Medicine, used a sample of 415,737 UK Biobank study participants who were between the ages of 40 and 69. The survey lasted from 2006 to 2010. Researchers asked participants about their dietary intake of non-oily fish and fish oil supplements, among other things. Nearly a third regularly used fish oil supplements. Usage also tended to be higher in women, older adults, and White participants.

The participants were then followed until March 2021 or death, to assess the long term effects of fish oil use, specifically in respect to cardiovascular disease. Over the monitoring period, 18,367 participants reported atrial fibrillation (irregular heart rates), 22,636 had a heart attack/stroke or heart failure, and 22,140 died.

The participants who were in good cardiovascular health at the start of the study were more likely to develop heart issues like atrial fibrillation and strokes. Interestingly enough, those who started the survey with cardiovascular disease had a lower risk of developing heart issues. That is, the fish oil appeared to help those with existing heart disease.

Researchers also analyzed how age, sex, smoking, and other factors played a role in such associations. Women and non-smokers who regularly used fish oil supplements had a higher risk of developing cardiovascular issues.

This study was purely observational, so it’s unclear if fish oil itself caused the heart issues, or were indeed protective in the participants who already had cardiovascular disease. It also wasn’t completely controlled — the participants were not all taking the same doses or formulations of fish oil supplements.

“Further studies are needed to determine the precise mechanisms for the development and prognosis of cardiovascular disease events with regular use of fish oil supplements,” the authors write in the conclusion.

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