Don’t take regular fish oil capsules to prevent heart disease

2. Don’t take regular fish oil capsules to prevent heart disease

Cost: It costs roughly 1 to 3 yuan per day, or 400 to 1000 yuan per year. Taking it requires no extra time at all.

In plain terms: Two large trials enrolled 26000 and 15000 people with diabetes respectively. For those who took 1 gram of fish oil daily, the rates of major cardiovascular events and death were identical to those who did not take it. The fact that eating fish is beneficial does not mean fish oil capsules are equally helpful. Skipping them saves you 400 to 1000 yuan each year.

Benefit: The VITAL trial included 25871 participants who took 1 gram of fish oil daily for a median follow-up of 5.3 years. No difference emerged between groups in terms of major cardiovascular events or death. The hazard ratio for major cardiovascular events was 0.92 (a hazard ratio of 1 indicates no difference); its 95% confidence interval of 0.80–1.06 also confirms no meaningful difference. The hazard ratio for all-cause death was 1.02 (0.90–1.15). The ASCEND trial involved 15480 diabetic patients who took the same daily dose for an average of 7.4 years, and again no significant differences were observed: the relative risk for serious vascular events was 0.97 (0.87–1.08) and for all-cause death it was 0.95 (0.86–1.05). The perception that fish oil is worthwhile stems from many people mistakenly equating the health benefits of eating fish with those of fish oil capsules.

Evidence grade: A

Sources: Manson JE et al. (2019). Marine n-3 Fatty Acid Supplements and Prevention of Cardiovascular Disease and Cancer. NEJM. <https://doi.org/10.1056/NEJMoa1811403>; ASCEND Study Collaborative Group (2018). <https://doi.org/10.1056/NEJMoa1804989>; Bhatt DL et al. (2019). Cardiovascular Risk Reduction with Icosapent Ethyl for Hypertriglyceridemia. New England Journal of Medicine. <https://doi.org/10.1056/NEJMoa1812792> (note the high-purity prescription fish oil trial)

Notes: Controversy: One trial did produce positive results. The REDUCE-IT trial enrolled 8179 participants with existing cardiovascular disease or diabetes, who were already taking statins and had elevated triglyceride levels (135–499 mg/dL). They took 4 grams of prescription-grade pure EPA daily, which lowered their risk of adverse events to 17.2% from 22.0%. This represents roughly a quarter reduction in risk (hazard ratio 0.75, 0.68–0.83). However, this was a high-dose prescription medication given to high-risk patients, not ordinary over-the-counter fish oil supplements. Eating fish itself is not covered by these findings.