Written by Joyce Smith, BS. This study suggests that habitual use of fish oil is associated with a lower risk of all cause cardiovascular disease (CVD) and mortality and provides a marginal benefit against CVD events among the general population.
Fish oil supplements, rich in long-chain polyunsaturated omega-3 fatty acids, primarily eicosapentaenoic acid and docosahexaenoic acid 1, have been recommended daily for the prevention of cardiovascular disease (CVD) 2,3 and have received widespread use in developed countries 4; yet, conflicting study findings have obscured the role of omega-3s in the prevention of CVD. 5. A recent large VITAL (Vitamin D and Omega-3 Trial) randomized controlled trial 6 found that Omega-3 fatty acids significantly reduced myocardial infarction risk but not risks of CVD events, prompting Li and colleagues to examine data from the UK Biobank, a population-based cohort of 427,678 men and women from England, Scotland, and Wales. Included in their analysis were 427,678 participants (ages 40 – 69; 55% women) who were enrolled from 2006 – 2010 and followed up until the end of 2018, for a median of 8.1 years for CVD events and 9.0 years for mortality. 7 All participants filled out extensive questionnaires that included sociodemographic status, socioeconomic status, and lifestyle habit questions as well as use of fish oil supplements. All were CVD or cancer-free at baseline.
Analysis of the questionnaire data revealed that 133,438 (31.2%) of the participants habitually took fish oil supplements. Those who supplemented with fish oil were older and more likely to be female, non-smokers, physically active, and had lower rates of diabetes. The results also showed that fish oil users ate oily fish more frequently than non-users and had higher rates of hypertension and longstanding illness than non- users. In addition, fish oil users were more likely to take antihypertensive drugs, aspirin, vitamin supplements, as well as mineral and other dietary supplements.
Final analysis revealed significant inverse associations of fish oil use and risk of all-cause mortality and mortality from CVD events, myocardial infarcts and stroke (P< 0.05 for all). In multivariable adjusted models, the adjusted hazard ratios associated with fish oil use were 0.87 (95% CI 0.83 to 0.90) for all-cause mortality; 0.84 (0.78 to 0.91) for CVD mortality; 0.80 (0.70 to 0.91) for myocardial infarction mortality; 0.93 (0.90 to 0.96) for CVD; 0.92 (0.88 to 0.96) for myocardial infarction; and 0.90 (0.84 to 0.97) for stroke. However, researchers did not find a significant association between fish oil use and death from stroke (P=0.14). Subgroup analysis revealed stronger associations between fish oil and the risk of all-cause mortality among men (P for interaction=0.009) and current smokers (P for interaction = 0.009). For CVD events, the associations were stronger among those with existing hypertension (P for interaction=0.005)
Study limitations included the lack of detailed information on dose, formulation, and duration of fish oil use; the potential for confounding or reverse causality; and the difficulty in separating the effects of a healthy lifestyle from those of fish oil supplementation.
The present findings appear to contradict those of the Vital Trial, which failed to show that fish oil reduced major cardiovascular events. Li and team suggest that habitual use of fish oils can provide a marginal benefit for CVD outcomes in the general population, thus they support the use of fish oil for the prevention of mortality from all causes and CVD, and recommend future studies to determine the most clinically meaningful effective dose of fish oil supplements.
Source: Li, Zhi-Hao, Wen-Fang Zhong, Simin Liu, Virginia Byers Kraus, Yu-Jie Zhang, Xiang Gao, Yue-Bin Lv et al. “Associations of habitual fish oil supplementation with cardiovascular outcomes and all cause mortality: evidence from a large population based cohort study.” bmj 368 (2020).
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Posted April 29, 2020.
Joyce Smith, BS, is a degreed laboratory technologist. She received her bachelor of arts with a major in Chemistry and a minor in Biology from the University of Saskatchewan and her internship through the University of Saskatchewan College of Medicine and the Royal University Hospital in Saskatoon, Saskatchewan. She currently resides in Bloomingdale, IL.
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- Van de Werf F, Bax J, Betriu A, et al. Management of acute myocardial infarction in patients presenting with persistent ST-segment elevation: the Task Force on the Management of ST-Segment Elevation Acute Myocardial Infarction of the European Society of Cardiology. Eur Heart J. 2008;29(23):2909-2945.
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- Li ZH, Zhong WF, 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:m456.
