Omega-3 polyunsaturated fatty acids (PUFA) and omega-6 PUFA are considered essential fatty acids. However, most Americans appear to meet their need for omega-3s from a typical Western diet, which contains at least 1 to 2g of omega 3s (1). However, most of the omega-3 PUFA in modern diets comes from the shorter ALA from plants and especially vegetable oils like canola and soybean. It has long been speculated that the longer chain omega-3s (i.e. EPA and DHA) found in fish and fish oil may have additional beneficial metabolic effects that may help in the prevention and treatment of cardiovascular disease (CVD).

Eskimo Study Lead to the Theory that Omega-3s Help Prevent CVD

The idea that long-chain omega 3s might help reduce CVD started when it was reported that Greenland Inuits had very little CVD despite a diet high in fat and cholesterol. It was a study by Drs. Bang and Olaf published in the June 1971 edition of The Lancet that first suggested a possible connection between higher fish oil consumption and better heart health. This study analyzed the plasma-lipid pattern of 130 Greenland Inuits. The team determined the concentrations of plasma lipids, cholesterol, and triglycerides in both men and women age 30 or older and compared them to the levels in a Danish control group. In nearly all categories, lipid concentrations were significantly lower among Inuits than Danes. The average difference also tended to increase with age. These authors believed the high omega-3 fatty acid content of the Inuit diet may account for their lower blood lipid values. Data about Inuit health back then reflected very few deaths from heart attacks. The beneficial effects of omega-3s were suspected to be from not only lower blood lipids but also reduced inflammation, less tendency to form blood clots, and a reduced risk of heart rhythm problems.

Cochrane Review Finds Omega-3s Don’t Reduce CVD

However, a recent review article by the Cochrane group this past July examined 79 randomized trials with well over 112,000 subjects that failed to find any significant reduction in subjects taking omega-3 fish oils or a placebo (2). This review article looked at a variety of subjects, some with and some without known CVD. The proponents of fish oil still suggest that they might help certain people such as those with type 2 diabetes mellitus (DM) because they often have elevated serum triglycerides, and fish oils do lower serum TGs although they do not appear to lower serum cholesterol levels. However, we now know that contrary to what the early Eskimo studies suggested, omega-3s do not lower serum LDL-C and may raise LDL-C a bit on average. The fish oil proponents also suggest fish oil supplements may take five or more years to show a benefit.

This past August 26, 2018, the data from the long-running ASCEND study on the impact of omega-3 fatty acid supplementation on CVD in patients with diabetes were published. Since those with type 2 DM frequently have elevated serum TG levels and more inflammation and a 2-3-fold increased risk of CVD they seemed a group most likely to benefit from omega-3-rich fish oil supplements. The results of this large double-blind randomized controlled clinical trial on the efficacy of omega-3 supplementation were reported by Louise Bowman, MD, of the University of Oxford in England, at the annual congress of the European Society of Cardiology. The results of this ASCEND study were also published the same day online in the New England Journal of Medicine (3).

The ASCEND subjects all had diabetes (n=15,480) at the start of the study. Patients were randomized to daily 1 gram capsules of either omega-3 fatty acids or a similar capsule containing olive oil. Result showed after 7+ years of follow up that those taking the omega-3 supplements had the same odds of non-fatal heart attack or stroke, transient ischemic attack, or cardiovascular death as peers who got the olive oil placebo (8.9% versus 9.2%, RR 0.97, 95% CI 0.87-1.08).

Consideration of arterial revascularization in addition to serious vascular events still yielded no significant difference between groups (11.4% versus 11.5%, RR 1.00, 95% CI 0.91-1.09). No difference was seen for all-cause death either (9.7% versus 10.2%, RR 0.95, 95% CI 0.86-1.05). Additionally, the omega-3 and placebo groups shared similar rates of non-fatal serious adverse events (most commonly surgical/medical procedures). The results add to the growing literature that omega-3 consumption makes no difference in cardiovascular health, despite the fact that some clinical guidelines continue to recommend taking fish oil supplements to reduce the risk of congestive heart failure, coronary heart disease, ischemic stroke, and sudden cardiac death.

"Our results would suggest that current guideline recommendations should be reconsidered," Bowman said in a press conference. As it currently stands, many patients have been led to believe that taking fish oil pills will help prevent CVD events and some may ignore proven dietary advice for lower serum cholesterol and blood pressure because they think the fish oil supplements will protect them.

Bottom Line: The results of the ASCEND study and the recent Cochrane review add to the growing body of research that shows taking omega-3 supplements is of no help for treating or preventing CVD and will not reduce the risk of congestive heart failure, coronary heart disease, ischemic stroke, and sudden cardiac death. People taking these supplements need to know that fish oil supplements are likely a waste of money and might be harmful if people take them believing that these pills will protect them from future CVD events.

By James J. Kenney, PhD, FACN

References: 

1. https://ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/
2. https://www.bmj.com/content/362/bmj.k3149
3. https://www.nejm.org/doi/full/10.1056/NEJMoa1804989?query=main_nav_lg

One Last Note from Dr. Jay: It seems like every few years they come up with some new super supplement that will prevent and cure numerous ills and then after decades of research we realize it was 99% hype. Perhaps the "experts" will now admit they got another one wrong and stop with the fish oil supplement nonsense. Only people who can be helped with supplements are people who are deficient in the supplemented nutrient. Mega-doses of some nutrients might occasionally have a drug-like benefit but then they come with side effects that can largely negate whatever benefit they have. Just eat a largely whole foods, plant based diet and avoid foods rich in saturated fat, cholesterol, salt, and refined carbs and stay active and get enough sleep and you will likely live a lot longer and healthier life than most Americans.