Who isn’t concerned about heart health? More people are focusing on eating a heart-healthy diet and some take supplements in hopes of lowering their risk of cardiovascular disease. One of the most popular supplements people take for heart health is fish oil supplements. Fish oil is rich in long-chain omega-3 fatty acids called EPA (eicosatetraenoic acid) and DHA (docosahexaenoic acid). Fish oil supplements have become popular since several studies showed that long-chain omega-3s reduced the risk of dying from heart disease and stroke.
Recent studies, however, did not find that fish oil or long-chain omega-3s lowered the risk of cardiovascular disease. The death rates from cardiovascular disease and stroke were similar between groups who took fish oil and those who did not. These results are a disappointment for people who take a fish oil supplement each day. This was a large, randomized controlled study involving 13,000 people, called the STRENGTH trial.
Research doesn’t stop with a single study and sometimes studies contradict one another. Another trial called the REDUCE-IT trial also looked at the value of omega-3 fatty acids from fish oil on cardiovascular risk. The findings were quite different. In this trial, omega-3s lowered the risk of dying of cardiovascular causes. In this trial, taking 2 grams of purified EPA two times per day reduced the risk of heart attack and stroke relative to taking a placebo. Both were large well-conducted studies. Why the discrepancy?
The difference is the formulation of fish oil they used. STRENGTH used an omega-3 supplement that contained DHA and EPA, while REDUCE-IT used pure, high-dose EPA. The REDUCE-IT trial was the first to investigate high-dose EPA without DHA. The conclusion? Based on these findings, fish oil supplements that contain high dose EPA and little or no DHA may offer more benefits than a combination EPA and DHA supplement.
Could Fish Oil Be Harmful to Heart Health?
A more recent study raised further concerns about taking a combination of DHA and EPA fish oil supplements. This study found that people who took more than 1 gram per day of a combination fish oil supplement had a higher risk of developing an irregular heart rhythm called atrial fibrillation.
Atrial fibrillation is a common rhythm abnormality where the heart rate becomes “irregularly irregular”. The upper chamber of the heart beats erratically, throwing off the heart rhythm. Although medications help control atrial fibrillation, people who have it are at a higher risk of developing strokes. For this reason, some people with it must take blood thinners. Atrial fibrillation is more common in men and becomes more prevalent with age. Other risk factors for atrial fibrillation include:
- A history of heart disease
- Hypertension
- Consuming excessive alcohol
- Obesity
- An overactive thyroid gland
- Sleep apnea
- Metabolic syndrome
Some studies also link long periods of intense exercise, like running marathons, with atrial fibrillation in men. However, moderate amounts of exercise appear to lower the risk of this common heart rhythm abnormality.
In the study, subjects who consumed more than a gram of fish oil per day had a higher likelihood of developing atrial fibrillation. Most people who take a fish oil supplement take between one and three grams daily. Are these people placing themselves at higher risk for atrial fibrillation? It’s still not clear.
The Bottom Line
Despite these findings, the American Heart Association still recommends consuming two servings of fatty fish per week for heart health. Omega-3s have anti-inflammatory benefits, and they help balance the omega-6 fatty acids that most people get too much of. In ancestral times, humans got a ratio of omega-3s to omega-6s of around 4 to 1. In modern society, it’s closer to 15 to 1.
Getting a higher quantity of omega-3s to omega-6s, toward the 4 to 1 end, may help reduce inflammation. Since inflammation is damaging to the inner walls of blood vessels, an anti-inflammatory diet may lower the risk of cardiovascular disease. For example, studies link the Mediterranean diet with a reduced risk of heart attack and stroke. Long-chain omega-3s also help reduce blood triglycerides, and that’s beneficial for heart health.
Until we know more about long-chain omega-3s and what form is best, you’re best off getting long-chain omega-3s from fatty fish rather than fish oil supplements. When you get your omega-3s this way, you also get the protein and other nutrients in the fish.
It may turn out that taking a supplement that’s mostly EPA offers heart health benefits while the combination of DHA and EPA doesn’t. Then there’s atrial fibrillation risk, another issue that needs sorting out. Until then, get omega-3s from food sources, unless your doctor recommends taking a fish oil supplement.
Are fish oil supplements more hype than science? That remains to be seen, but fatty fish is a nutrient-dense source of protein and long-chain omega-3s. Until then, food might be the safest way to get omega-3s.
References:
- “Omega-3 fatty acids and the heart: New … – Harvard Health.” 24 Mar. 2021, health.harvard.edu/blog/omega-3-fatty-acids-and-the-heart-new-evidence-more-questions-2021032422213.
- N Engl J Med 2019; 380:11-22. DOI: 10.1056/NEJMoa1812792.
- “New Cochrane health evidence challenges belief that omega ….” 18 Jul. 2018, cochrane.org/news/new-cochrane-health-evidence-challenges-belief-omega-3-supplements-reduce-risk-heart-disease.
- “Omega-3 Fatty Acids – Health Professional Fact Sheet.” //ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/.
- Nicholls SJ, Lincoff AM, Garcia M, Bash D, Ballantyne CM, Barter PJ, Davidson MH, Kastelein JJP, Koenig W, McGuire DK, Mozaffarian D, Ridker PM, Ray KK, Katona BG, Himmelmann A, Loss LE, Rensfeldt M, Lundström T, Agrawal R, Menon V, Wolski K, Nissen SE. Effect of High-Dose Omega-3 Fatty Acids vs Corn Oil on Major Adverse Cardiovascular Events in Patients at High Cardiovascular Risk: The STRENGTH Randomized Clinical Trial. JAMA. 2020 Dec 8;324(22):2268-2280. doi: 10.1001/jama.2020.22258. PMID: 33190147; PMCID: PMC7667577.
- “Fish oil – Mayo Clinic.” 08 Dec. 2020, https://www.mayoclinic.org/drugs-supplements-fish-oil/art-20364810.
- “How the Mediterranean diet lowers risk of cardiovascular ….” 11 Dec. 2018, https://www.nhlbi.nih.gov/news/2018/how-mediterranean-diet-lowers-risk-cardiovascular-disease.
- Delgado-Lista J, Perez-Martinez P, Garcia-Rios A, Perez-Caballero AI, Perez-Jimenez F, Lopez-Miranda J. Mediterranean Diet and Cardiovascular Risk: Beyond Traditional Risk Factors. Crit Rev Food Sci Nutr. 2016;56(5):788-801. doi: 10.1080/10408398.2012.726660. PMID: 25118147.
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