Pros and Cons: Fish Oil Supplements

Fish oil supplements are among the most popular dietary supplements taken by Americans as nearly 8% of adults — roughly 19 million people — take them. And why? The pills contain omega-3 fatty acids that have been associated with a variety of health benefits, including helping with arthritis, cardiovascular disease, lower cholesterol and triglycerides (a type of fat found in the blood), and even depression.

But is all the hype surrounding fish oil pills backed up by scientific evidence? And are there any side effects that are concerning with the use of them?  There is no doubt that omega-3s are absolutely necessary for human health, and much research has been done on whether the supplements offer any real benefits, but studies often yield conflicting or inconclusive results.

Before examining the pros and cons of fish oil pills, it’s important to start with an understanding of the different kinds of omega-3s, how they work in the body and what studies have been conducted to either support or undermine the supposed health benefits of the supplement.

Why the Fish Oil Craze?

The popularity of fish oil has grown along with the large body of research linking a wide array of health benefits, especially lowering blood pressure, triglycerides, and cholesterol, with omega-3 fatty acids. The main types of omega-3s are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are found mainly in seafood, and alpha-linolenic acid (ALA) which is found in flaxseed and vegetable oils, walnuts, and leafy vegetables. Fish oil supplements often contain a combination of EPA and DHA.

Omega-3s are found in the membranes of every cell in the body. “There are lots of omega-3 fatty acids in cell membranes of the brain and the nervous system in general, as well as in the heart, and they affect how different transmitter systems act,” says Jeppe Hagstrup Christensen, MD, a clinical professor at Aalborg University Hospital in Denmark who has conducted multiple studies on the topic. “Omega-3s are incorporated into these tissues when ingested, and their concentration increases. You can actually measure the increase of the fatty acids in different tissues after supplementation.”

The body requires omega-3 fatty acids for proper brain development and functions like blood clotting, digestion, fertility, and cell and muscle activity.

“Omega-3 fatty acids are essential fats — they must be consumed for normal body functions, and they are not manufactured by the body,” says Jonathan Fialkow, MD, chief clinical integration officer of Baptist Health South Florida and medical director of the Cardiovascular Research Center of South Florida. They are needed in order for the body to make various substances that regulate inflammation and blood clotting, and there is evidence that they “protect our cells from oxidative stresses that can otherwise lead to cell damage.”

What Are Some of the Purported Benefits?

Omega-3 supplements have been associated with a range of mental and physical health benefits. In a study published in the Journal of Nutrition, for example, a small, daily dose of fish oil led to a reduction in blood pressure after eight weeks. Some findings suggest that fish oil consumption may lower cholesterol in menopausal women, and in patients with metabolic syndrome particularly when combined with olive oil. And at amounts available by prescription, fish oil can lower triglycerides.

Multiple studies have shown improvements in rheumatoid arthritis (RA) symptoms when patients add omega-3s to their therapy. In a study of 60 people with RA published in the Global Journal of Health and Science, researchers gave half of the group omega-3 capsules and the other half a placebo. All of the patients were on standard RA drug therapy, including three doses per day of  prescription nonsteroidal anti-inflammatory drugs (NSAIDs) for pain. After 12 weeks, 72% of those taking fish oil were able to reduce or discontinue taking their pain meds. Patients on the placebo were not able to cut back on their pain meds.

In a review of 23 studies of fish oil for RA symptoms, researchers determined that there was a consistent, though modest, benefit of fish oil on joint swelling and pain, duration of morning stiffness, disease activity, and the use of NSAIDs. Published in the British Journal of Nutrition, the analysis also noted that in almost all the trials patients also reported that it took longer for them to get fatigued, and they experienced an increase in grip strength.

Numerous studies have also linked fish oil supplementation with reduced symptoms of ADHD (attention deficit hyperactivity disorder) in children, and others have found that children whose mothers consumed fish oil supplements during pregnancy had lower rates of allergic diseases such as eczema and food allergies in the first 12 months of life. Other research has found a connection between omega-3 supplementation and a decrease in depression symptoms.

People suffering from depression are often deficient in omega-3 fats, which help regulate mood, explains Taz Bhatia, MD, an integrative medicine expert at CentreSpringMD in Atlanta.

But Does It Really Work?

While these studies point to many benefits of fish oil supplements, findings have generally been correlational (as compared to causative), and in some cases, other research shows conflicting results. Although a number of studies have indicated that omega-3 supplementation may help prevent heart disease, for instance, most have not observed this effect.

However, there is substantial evidence to suggest that supplements could help individuals who already have an elevated risk of heart disease. In a review that Fialkow published in the American Journal of Cardiovascular Drugs, he reports that omega-3 products have demonstrated reductions in triglycerides and total cholesterol — two factors that influence heart health — in high-risk patients.

Here’s the catch, though: Those heart-helping benefits are likely to come only from prescription versions of omega-3s, not the kind sold over the counter — and many physicians may not even know that.

One prescription version, Vascepa (icosapent), was FDA approved in 2012 to reduce triglyceride levels when taken along with a healthy diet. The drug was indicated for people with severely high triglyceride levels — at least 500 mg/dL.

In December 2019 Vascepa received additional approval to reduce the risk of heart attack, stroke and other cardiovascular events in people with triglycerides of at least 150 mg/dL when taken along with the highest dose of statins that the person can tolerate. Benefits of the drug were shown in a five-year study of 8,179 patients with high triglycerides who were taking statins. The new approval applies to people who have established cardiovascular disease or diabetes and at least two additional risk factors for cardiovascular disease.

The active ingredient in Vascepa is the omega-3 fatty acid eicosapentaenoic acid. Fialkow explains that different fatty acids compete with each other in cell membranes, and a diet that is rich in one particular kind of fat — like omega-6 fatty acids, which are found in foods like fats and oils, cereal products, meat, and poultry — may replace the benefits of another type of fat, like omega-3s.

“Dietary supplements do not have a concentration of omega-3 sufficient to reliably raise your omega-3 level compared to other fats, which are contained in the supplements as well,” he explains.

“In addition, as a poorly regulated industry, many dietary supplement fish oils don’t contain the amount of omega-3 promoted on the label and may have impurities in their manufacturing which may inhibit the ultimate omega-3 benefit,” Fialkow added. Indeed, an analysis by scientists at Purdue University, published in the Journal of the Science of Food and Agriculture,  discovered that over 70% of supplements tested did not contain the full amount of EPA or DHA stated on the label. (For more on problems with label claims in the supplement industry, see MedShadow’s Fish Oil or Snake Oil? The Problem With Supplements.

In a 2017 American Heart Association (AHA) science advisory, a committee of cardiology experts says that the clinical evidence falls short of recommending that the general public take fish oil pills to curb the risks of developing cardiovascular disease.

“People in the general population who are taking omega-3 fish oil supplements are taking them in the absence of scientific data that shows any benefit of the supplements in preventing heart attacks, stroke, heart failure or death for people who do not have a diagnosis of cardiovascular disease,” David Siscovick, MD, MPH, chair of the writing committee, said of the new advisory, published in the journal Circulation. The committee reviewed randomized clinical trials that looked at whether fish oil pills were effective at preventing cardiovascular disease. The 2017 advisory updated a

2002 AHA advisory, which stated that the supplements are beneficial for people who have recently had a heart attack. The new advisory adds that people with heart failure may also benefit from fish oil.

A 2019 science advisory from the American Heart Association (AHA) agrees with Fialkow’s assessment. The AHA says that 4 grams a day of prescription omega-3s can lower triglycerides by 20% to 30% in most people with high triglycerides. However, the AHA does not recommend OTC omega-3 supplements for high triglycerides because they are not FDA-regulated and therefore their potency, quality, and efficacy are not assured. In 2019 the Food and Drug Administration (FDA) approved the use of qualified health claims for high blood pressure and coronary heart disease in the labeling of fish oil supplements and foods. After reviewing 717 publications presented by an omega-3 industry group, the FDA determined that the evidence didn’t meet the “significant scientific agreement” standard required for an authorized health claim. However, it did meet the “credible evidence” standard.

What this means is that the FDA doesn’t object to fish oil supplement labels stating that EPA and DHA may help lower blood pressure, and thus reduce the risk of coronary heart disease. But this claim must be followed by a disclaimer that evidence for these benefits is inconsistent and inconclusive. For more on potential problems with marketing claims of fish oil benefits, see MedShadow’s The Troubling Marketing Behind a Prescription Fish Oil Pill. In a large study known as VITAL, researchers followed nearly 26,000 people over age 50 for more than five years to determine if fish oil could prevent cardiovascular events (heart attack, stroke, or death from cardiovascular causes) or invasive cancer of any type. Study participants, who were considered at usual risk for these diseases, took either 1 gram per day of prescription fish oil or a daily placebo.

Published in 2018 in the New England Journal of Medicine, the study reported that fish oil supplements did not reduce the risk of cancer or major cardiovascular events. However, in people who ate less than 1 ½ servings (one serving was 3 to 4 ounces) of fish per week, the risk of cardiovascular events was reduced by 19%. And when heart attack and stroke were looked at separately from overall cardiovascular events, fish oil appeared to reduce the risk of heart attack by 28%, and fatal heart attack by 50%.

In a 2018 review of studies to assess fish oil’s ability to reduce cardiovascular risk, researchers collected data from 10 trials, which consisted of 77,917 people who were around 64 years old and had a high risk of heart disease.

After analyzing the large trials, which lasted for nearly 4 ½  years, the team concluded that omega-3 supplements failed to reduce coronary heart disease and other major heart conditions in people who have or are at high risk of developing cardiovascular disease. Writing in JAMA Cardiology, the group also says that there is a lack of evidence supporting the use of fish oil in the general population to prevent cardiovascular disease. The results “provide no support for current recommendations,” the researchers write.

In another 2018 study, published in the New England Journal of Medicine, fish oil pills did not help to prevent cardiovascular problems in people with diabetes. People with diabetes were randomized and given one of four treatments: fish oil and aspirin, fish oil and placebo, aspirin and placebo fish oil (olive oil); or two placebos. Participants were followed for an average of 7 ½  years. Overall, 8.9% of those who took a fish oil supplement had a serious cardiovascular event, such as a heart attack or stroke, compared to 9.2% of those given the fish oil placebo, a difference not considered statistically significant. During the study, 9.7% in the fish oil group died, compared to 10.2% taking the olive oil placebo, also statistically about the same.

Another 2018 review of clinical trials found that omega-3 supplements do not provide any benefit in reducing the risk of cardiovascular disease.

The Cochrane review examined 79 trials and more than 110,000 participants. Results found that increasing intake of EPA and DHA, the two main types of omega-3 fatty acids, made little or no difference in reducing cardiovascular death or events, stroke or other heart irregularities. Omega-3 fatty acids, however, did tend to reduce triglycerides and increase HDL, better known as “good cholesterol.” There was also low-quality evidence that ALA may slightly reduce the risk of cardiovascular disease events, death from chronic heart disease and irregular heartbeats.

What Are the Risks?

There are very few risks associated with omega-3 supplements. They can cause gastrointestinal symptoms like diarrhea or indigestion in some people, and they may be unsafe for people with seafood allergies.

Because of the anti-clotting properties of these supplements, people taking blood-thinning medications or NSAIDs such as over-the-counter pain relievers should consult a healthcare provider before supplementing with omega-3 products.

While previous evidence suggested a connection between omega-3 supplementation and the risk of prostate cancer, a more recent review reported in Integrative Cancer Therapies concludes that such data is weak and requires further investigation.

The Bottom Line: Just Eat It

Although the downsides appear to be minimal, that may be beside the point. The bigger picture takeaway is this: Most people do not even need omega-3 supplements — they simply need to eat more foods rich in omega-3s.

“For people with healthy diets and normal metabolism, there should be no reason to take omega-3 supplements or prescriptions,” says Fialkow. Fatty fish like salmon, tuna and sardines are especially good sources of omega-3s, and the American Heart Association recommends that people eat at least two servings per week. Algal oil may be a good source of DHA for vegetarians, and vegans can get omega-3s from nuts, chia seeds and flaxseeds or flaxseed oil.