Fish oil supplements may cause harm to the heart, study finds

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Daily fish oil supplements are widely embraced for their heart-healthy omega-3 fatty acids, particularly among adults over 60, who make up about 20% of users in the United States. However, a recent study suggests that contrary to expectations, regular consumption of these supplements may elevate the risk of first-time stroke and atrial fibrillation in individuals with good cardiovascular health. Atrial fibrillation, characterized by irregular heartbeats, poses concerns about the efficacy and safety of fish oil supplementation. Cardiologist Dr. Andrew Freeman from National Jewish Health in Denver highlights the need for a critical reevaluation of the widespread use of over-the-counter fish oil supplements, which are not endorsed by medical guidelines despite their popularity.

Fish Oil Benefited Individuals Only with Pre-existing Heart Disease

The research, examining data from over 415,000 individuals aged 40 to 69 in the UK Biobank study, revealed that nearly a third of participants, tracked for an average of 12 years, reported regular fish oil supplement usage. Among those without pre-existing heart conditions, consistent use of fish oil supplements was linked to a 13% higher likelihood of developing atrial fibrillation and a 5% increased risk of experiencing a stroke, as detailed in the BMJ Medicine journal on Tuesday. Dr. Freeman highlighted concerns regarding the quality and purity of over-the-counter fish oil, noting potential issues with consistency, contaminants, and heavy metal content like mercury.

“In addition, studies over the last 10 years have not been very positive for over-the-counter fish oil,” he added. “Fish oil was either having no benefit or in some cases it may harm, such as with stroke and AFib. So that’s not new.”

The new study did find that individuals with existing heart disease at the beginning of the research had a 15% lower risk of progressing from atrial fibrillation to a heart attack and a 9% lower risk of progressing from heart failure to death when they regularly used fish oil.

Prescription versions of fish oil, such as Vascepa and Lovaza, are used to counter risk factors like high triglycerides in people with cardiovascular disease, Freeman said.

“But even in the prescription strength, highly purified versions of fish oil, the risk for AFib and sometimes stroke has also been present and doctors are cautious about that,” Freeman noted.

“Overall, I would say that the days where people just go to the store and buy buckets of fish oil pills to keep them well should be over, but fish oil may still have a role in people who are already sick.”

Opt for Food Sources of Omega-3s Instead

When it comes to fish oil, “the devil is in the details,” says Dr. Richard Isaacson, an Alzheimer’s preventive neurologist and director of research at the Institute for Neurodegenerative Diseases in Boca Raton, Florida. He emphasizes the importance of testing for omega-3 fatty acid levels before taking supplements, as not everyone needs them.

Isaacson recommends obtaining omega-3s from food sources, with sardines and wild-caught salmon being the best options due to their high levels of healthy unsaturated fats and lower mercury content. He advises against farm-raised salmon due to water impurities. Other good sources include lake trout, mackerel, herring, and albacore tuna, though he suggests limiting albacore tuna to twice a week due to mercury levels.

Nonfish sources of omega-3s include algae, seaweed, chia seeds, edamame, flaxseed, hempseeds, and walnuts. However, these plant-based omega-3s are a different form than those found in fish, and studies indicate they may be harder to metabolize in people with higher levels of omega-6s, another type of unsaturated fat primarily found in vegetable oils.

If supplements are needed

Prescription omega-3 fatty acids are considered superior to over-the-counter options due to their purity and quality. However, prescribed supplements can be expensive. For those opting for over-the-counter omega-3s, Dr. Richard Isaacson offers these tips to his patients:

First, ensure the freshness of the fish oil. Isaacson advises against purchasing from online or retail superstores like Amazon or Costco. “We recommend buying from only a handful of reputable companies, directly from their specific websites,” he says. The quality difference between fish oil stored in a hot warehouse near expiration and fresh fish oil sent directly from the company and kept in a home refrigerator is significant.

The US Food and Drug Administration does not regulate the supplement industry to ensure each product contains what it claims on the label or test for contaminants such as bacteria, heavy metals, pesticides, plastic residues, and other impurities.

However, some organizations have taken on this role by testing various supplements and some pharmaceuticals. Look for their labels before purchasing. The nonprofit organization US Pharmacopeia (USP) sets widely accepted standards for supplements, but ConsumerLab.com and NSF International also conduct third-party testing.