A cohort study done by UK Biobank evaluated the associations between frequently taking fish oil supplements and all-cause mortality, cardiovascular disease (CVD) mortality, and CVD events, and found marginal benefit against CVD events among the general population.
Fish oil, an abundant source of long chain omega 3 fatty acids, has become popular in the UK and other developed countries; however, despite recent studies, there have been considerable gaps in identifying proven fish oil benefits for cardiovascular health, and some studies have shown conflicting results.
The study incorporated a total of 427,678 men and women between the ages of 40 and 69 who had not been diagnosed with CVD or cancer at baseline, between 2006 and 2010 and with follow-ups until the end of 2018.
Participants were evaluated using a questionnaire that inquired about their habits using various supplements, among them fish oil. The questionnaire also had participants respond to sociodemographic questions such as age, sex, assessment center, ethnicity, and household income; socioeconomic status questions using the Townsend Deprivation Index; lifestyle habit questions such as smoking status, alcohol consumption, BMI, physical activity, diet; and questions on their comorbidities, if applicable.
Analysis of the questionnaire data revealed that 133,438 (31.2%) of the participants habitually take fish oil supplements. Those who supplemented with fish oil were older and more likely to be female, non-smokers, physically active, and have lower rates of diabetes. The results also showed that fish oil users ate oily fish more frequently than those who didn’t take fish oil and had higher rates of hypertension and longstanding illness than non-users. Those who supplement with fish oil were additionally more likely to take antihypertensive drugs, aspirin, vitamin supplements, as well as mineral and other dietary supplements.
Overall, the findings indicated that habitual fish oil supplementation was associated with a 13% lower risk of all-cause mortality, a 16% lower risk of CVD mortality, and a 7% lower risk of CVD events among the general population.
The results of the study align with several other previous studies that claimed the benefits of fish oil supplements in lowering the risk of CVD events. According to the study authors, possible explanations for the conflicting results of previous studies may be due to their insufficient sample sizes, events, and dosage of fish oil.
Insufficient evidence remains on defining which component of omega 3 fatty acids (docosahexaenoic acid, eicosapentaenoic acid, or docosahexaenoic acid and eicosapentaenoic acid) provides benefits for CVD events or all-cause mortality, and UK Biobank has determined that future studies are needed.
1. Li Z, Zhong W, Liu S, et al. Associations of habitual fish oil supplementation with cardiovascular outcomes and all cause mortality: evidence from a large population based cohort study. BMJ. 2020;368. doi https://doi.org/10.1136/bmj.m456.