March 10, 2021 -- People with heart disease who regularly ate fish had fewer heart attacks, strokes, and were less likely to develop heart failure or die compared with similar individuals who didn't eat fish, according to a new analysis.

Researchers analyzed data from four previous studies that included more than 191,000 people from 58 countries who answered a survey about their diets. They found no beneficial link from eating fish among people without heart disease.

"There is a significant protective benefit of fish consumption in people with cardiovascular disease," summed up Andrew Mente, PhD, a senior investigator on the study, published in JAMA Internal Medicine, and an epidemiologist at McMaster University in Hamilton, Canada.

"This study has important implications for guidelines on fish intake globally. It indicates that increasing fish consumption and particularly oily fish in vascular patients may produce a modest cardiovascular benefit," he said in a statement released by McMaster.

A little over a quarter of those included in the new study had a history or were at high risk for heart disease. Among these about 51,000 people, those who consumed on average at least two servings of fish weekly had a 16% lower rate of major cardiovascular events including heart attacks, strokes, diagnoses of congestive heart failure and cardiac-related sudden deaths during a median follow-up of about 7.5 years. These events occurred in 17% of people with heart disease or at high risk for it.

The rate of death from any cause was a 18% lower among people with heart disease who ate two or more portions of fish each week compared with those who didn't. During follow-up, death from any cause occurred in 13% of the people who had heart disease or were high risk.

The researchers saw no additional benefit when people regularly ate greater amounts of fish.

’A Large Body of Evidence‘ to Benefit the Heart

Given the potential benefit and limited risk, "I think everyone should aim to eat two servings of fish each week, preferentially oily fish. That's very solid," says Dariush Mozaffarian, MD, DrPH, a cardiologist and dean of the Tufts Friedman School of Nutrition Science, in an interview with JAMA Internal Medicine that accompanies his commentary.

Oily, dark fishes include salmon, tuna steak, mackerel, herring, and sardines. Species such as these contain the highest levels of long-chain omega 3 fatty acids.

"If there is benefit from fish it's from the omega 3s, and all-in-all the evidence supports this," Mozaffarian says, though he notes the evidence is primarily observational, so it can only show linkage and cannot prove causation. Mozaffarian has received personal fees from food companies and drug companies developing or selling omega-3 pills.

The investigators did not have adequate data to compare diets with oily fish vs less oily fish.

For people who either can't consume two fish meals a week or want to ensure their omega 3 intake is adequate, "it's very reasonable for the average person to take one over-the-counter fish oil capsule a day," Mozaffarian adds.

He acknowledges that several studies of fish oil supplements failed to show benefit, but several others have. "It's a confusing field, but the evidence supports benefit from omega 3s," he concludes.