Fish Oil: Looking for Proof to Tip the Scales


Millions of Americans take fish oil supplements every day in hopes of preventing heart disease, depression, and even premature birth. It is one of the most popular nutritional supplements in the US

There has been a myriad of research into fish oil supplements, but questions remain about their benefits.

Many studies so far indicate that the dietary supplements do not offer the benefits that marketers are touting. A recent large, randomized clinical trial found that fish oil at a dosage found in many supplements does not reduce the incidence of heart disease or cancer, the main benefits it is associated with.

However, scientists are continuing to investigate the possible effects on heart health, including some other results in the large study recently conducted. They also delve deeper into potential effects that have been less well studied: on depression, cognition, autism, and other disorders.

“We really don’t have a jury yet,” said Joann Manson, director of preventive medicine at Brigham and Women’s Hospital at Harvard, who led the recent study on fish oil, heart health and cancer.

Despite the debate, sales of fish oil supplements rose 1.8% to around $ 1.2 billion in 2017, according to the Nutrition Business Journal.

The main components of fish oil, two polyunsaturated fatty acids known as eicosapentaenoic acid or EPA, and docosahexaenoic acid or DHA are found in the membranes of cells throughout the body. Although these fatty acids are essential for cell function, the human body has difficulty producing them itself and therefore has to get them from food. EPA and DHA are found in high amounts in oily fish such as salmon.

In the 1970s, researchers discovered that Inuit, whose diet consisted primarily of the fish they caught in the ocean, had minor cardiovascular problems. That finding spawned thousands of studies on the potential benefits of omega-3 fatty acids, a recommendation by the American Heart Association that people eat fish at least twice a week to help prevent heart disease, and an industry of fish oil supplements manufacturers.

Today the recommendation is to eat more fish. So far, fish oil supplements “cannot replicate these benefits,” says Craig Hopp, associate director of the extramural research division at the National Center for Complementary and Inclusive Health, a branch of the National Institutes of Health that conducts scientific research into health practices and products outside of the world Funded conventional medicine. NCCIH is currently funding studies to determine whether omega-3 fatty acids may increase the effects of antidepressants, reduce inflammation, and help children with autism spectrum disorders.

The problem is the same when trying to reproduce the benefits of fruits and vegetables with vitamins or supplements, he says. Trying to understand exactly what “is responsible for these benefits in a diet is hard to pinpoint,” he says, noting that “it is probably not just a thing.”

Researchers have identified several benefits. High doses of fish oil can reduce triglycerides, a type of fat in the blood that can increase your risk of heart disease. Some high triglyceride patients take prescription medications, the dosages and ingredients of which are different from over-the-counter supplements.

A recent study found that increasing intake of omega-3 fatty acids, particularly EPA and DHA, reduced the risk of premature birth – a finding that could give fish oil supplements a boost as many pregnant women worry about contaminants in fish, said Duffy MacKay, senior vice president of scientific and regulatory affairs for the Council for Responsible Nutrition, a trade association representing nutritional supplement manufacturers. (Industry standards limit contaminants like heavy metals in fish oil supplements and how they can be tested and filtered out, he says.)

Ultimate Omega from Nordic Naturals.


Nordic Naturals

Dr. Manson-conducted study, which was funded by multiple NIH institutes and tracked 25,871 men aged 50 and over and women 55 and over for more than five years, found that one gram of fish oil per day did not reduce the risk of heart disease or invasive cancer. However, the researchers also found a 28% lower risk of heart attack in participants who took fish oil. The benefit was even greater – a 40% reduction – for participants who took fish oil and ate less than 1.5 servings of fish per week.

The results were the focus of the study and need further investigation, warns Dr. Manson. Still, she says, “We believe there is a promising signal of cardiac health benefit.”

“There is tantalizing evidence that there might be something there,” says Pieter Cohen, an associate professor at Harvard Medical School and the Cambridge Health Alliance who studies nutritional supplements. He says they should be studied further, but they also need to be linked to many previous studies that show no benefits for heart disease. “If someone comes up to me and says I’m worried that I don’t have enough omega-3s, I would say I’m eating fish instead of taking a supplement,” he says.

The finding that omega-3s can help prevent premature birth should also be approached with caution, he says. “The ideal would be to follow these women and their babies so we can have more information,” he says.

Using data from the same large study led by Dr. Manson, the researchers are analyzing the effects of the fish oil regime on depression, cognition, diabetes, chronic pain and other disorders, says Dr. Manson. Results are expected in the next six months to a year, she says.

Olivia Okereke, director of geriatric psychiatry at Massachusetts General Hospital who leads analysis on depression, hopes she will provide answers that previous, smaller, and shorter observational studies don’t have. The researchers analyze participant data for diagnoses of depression as well as self-reported mood symptoms and how they differ over time, she says.

The alpha and omega-3 on fish oil supplements

The judges are still unsure whether fish oil supplements have benefits for a variety of health conditions. If you are taking supplements, here are some things to know.

  • Check how much eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) a supplement contains. These are the long chain omega-3 fatty acids that are the key components of a fish oil supplement. Avoid products that don’t state exactly how much EPA and DHA they have.
  • There is no government recommended daily value. The U.S. dietary guidelines recommend eating seafood in amounts equivalent to 250 milligrams of EPA and DHA per day. The Food and Drug Administration says that supplement labels should recommend no more than 2 grams of EPA and DHA daily, although doctors may prescribe more for patients who need to lower their triglycerides. Everyone’s needs are different. So speak to your doctor. You can have a blood test to see how much EPA and DHA are in your blood.
  • Fish oil supplements shouldn’t smell or taste fishy. Good quality fish oil is processed to prevent oxidation, which causes the fats to break down and smell.
  • Side effects of taking fish oil supplements are rare, but they can include heartburn, nausea, or diarrhea. Patients taking fish oil and blood-thinning medications such as warfarin should be monitored by their doctors, as high doses of the fish oil can increase the risk of bleeding.

Write to Betsy McKay at

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