Should I Take Fish Oil?

In 1971, a team of Danish researchers found that an Inuit population in Greenland had lower cholesterol levels and incidence of heart disease than Danes and Inuits who lived in Denmark. A theory arose: The indigenous people’s high marine-fat diet gave them heart protections.

Since then, fish oil and omega-3 fatty acids — the health-boosting star component of fish oil — have been the subject of tens of thousands of papers exploring their health benefits.

Today, the “Eskimo theory” has been largely discredited. “We really don’t know if the Eskimos got heart disease or not,” said Malden C. Nesheim, an emeritus professor of nutrition at Cornell University, who chaired an Institute of Medicine committee assessing the risks and benefits of seafood in the early 2000s, in a 2018 interview with The New York Times. “I’ve been an omega-3 skeptic since doing this study.”

What do proponents of fish oil say it will do for you?

Fish oil is said to: improve arthritis; reduce ADHD; reduce the likelihood of heart attack and cancer; improve high-density lipoprotein (HDL, the so-called good) cholesterol.

Should I try fish oil supplements?

For healthy individuals, fish oil supplements are unnecessary. It’s better to eat a few servings of fish a week, instead.

The largest study — called the Vital study — done by Brigham and Women’s Hospital, an affiliate of Harvard Medical School, followed more than 25,000 people since 2010 and focused on whether taking daily dietary supplements of vitamin D or omega-3 fatty acids reduced the risk of cardiac events or cancer in otherwise healthy individuals.

It found that omega-3 supplements didn’t reduce the risk of major cardiac events in a usual-risk population, but did reduce the risk in a subset of people with low fish intake by 19 percent. The study is considered the medical gold standard.

African-Americans benefited regardless of fish intake, showing a 77 percent lower risk of heart attack. “This could be a chance finding,” said Dr. JoAnn Manson, a director of the study and the chief of the Division of Preventive Medicine at Brigham and Women’s Hospital. “We do plan to pursue it in greater detail and try to replicate it in a separate trial because if this can be reproduced, that would be a very dramatic benefit to African-Americans.”

Because there is still more research to be done, experts don’t necessarily recommended that African-Americans take omega-3.

If you have some history of heart disease or high triglycerides (an estimated 25 percent of adults in the United States do, according to data from the National Health and Nutrition Examination Survey in 2015), it may be a good idea to take omega-3.

The potential downside, because supplements are not regulated, is that production isn’t standardized so we don’t know what’s in them, according to Dr. Pieter Cohen, of Cambridge Health Alliance, who is an associate professor of medicine at Harvard Medical School.

He said that supplements are expensive and that money could alternatively be spent on a healthier diet. As an internist, Dr. Cohen has seen negative behavioral effects in some of his patients who take supplements.

“I have many patients who are like, ‘I’ll take my supplement and then I won’t worry about eating healthfully during the day,’” Dr. Cohen said. “That’s really misguided. Because in this case we have absolutely no evidence that replacing a healthy meal of fish with an omega-3 supplement is better.”

Does more omega-3 equal healthier?

Not necessarily. The impact of omega-3 has been studied as it relates to the nervous system and brain health and in conditions like ADHD, Alzheimer’s disease and autoimmune diseases, for example.

But so far, the results have been inconclusive and inconsistent. “We need large-scale trials with very rigorous assessment of end points to understand the effects,” Dr. Manson said. Within the next several months, she and her team who worked on the Vital study will be reporting results on several ancillary studies of omega-3 on areas like cognition, depression, autoimmune disorders, kidney function and respiratory health.

How do I consume more omega-3 without pills?

• Eating fatty fish lowers LDL and triglycerides.

• Wild sockeye salmon tends to be low in pollutants and high in omega-3s, said Paul Greenberg, the author of “The Omega Principle,” which explores the health impacts of omega-3 and the environmental impact of its production.

• As an alternative, you can eat small fish like sardines, anchovies and herring.

• Flax seed oil is a plant-based source of omega-3, Dr. Manson said.

• If you want a pill supplement, look for a label from the United States Pharmacopeia, a nonprofit that establishes standards for medicines and supplements. “If a product has the U.S.P. label, it’s saying it’s abiding by the U.S.P. standards and can be legally held to those standards,” said Craig Hopp, of the National Center for Complementary and Integrative Health.

If I want to take omega-3 supplements anyway, will they hurt me?

No, but if you take excessive amounts in supplement form, you could get an upset stomach. There is also some evidence that certain omega-3s contribute to prostate cancer, although the findings are still coming together.

“The caution always with supplements is that unfortunately, there are many examples of what’s on the label is not what’s in the pill,” Dr. Hopp said. “There can be things missing. Not having the amount of EPA and DHA that’s specified. Or there can be things added to them.”

Where does fish oil come from?

It’s derived from cold-water fish, like salmon, sardines and mackerel. “The interest in them is they contain certain fatty acids,” Dr. Hopp said. Side note: The fish don’t produce omega-3 fatty acids internally; they get them from the tiny plants, plankton (and other stuff) they eat.

Am I destroying the environment by taking fish oil supplements?

Maybe? The way the pills are created contributes to the destruction of marine life balance, according to Mr. Greenberg, who explored this in his book. He explains that the reduction industry, which produces supplements and also feed for animals, including farmed fish, gobbles up 25 million metric tons of small fish a year to “boil them down to oil and meal.”

This leaves a hole in the food chain, where larger fish, marine mammals and seabirds are missing small fish, like the Peruvian anchoveta (one of the most highly fished fish in the world, with most of it going to the reduction industry), to eat.

“If you don’t have those little fish in between the planktonic level of life and the higher levels of life, there’s no way to translate the solar energy that hits the ocean from the planktonic level to higher life-forms,” Mr. Greenberg said. “The argument goes that if you left more of this little fish in the water, there’d be a lot more big fish out there to eat, populate the ocean, and to make it a more abundant place.”

To discourage this cycle, he suggests taking a supplement like a vegan, algae-based omega-3 that is sustainably sourced and doesn’t involve the reduction industry.