Fish oil may not prevent heart disease after all

Fish oil capsules. (Bigstock) Fish oil capsules. (Bigstock)

In 1968, an anonymous editorial in the Danish Medical Society’s weekly journal laid bare a puzzling pattern of disease among Inuit in Greenland. Coronary artery disease (CAD), the most common type of heart disease, was strangely uncommon among the Inuit. The author called on Danish researchers to study the tribes “before it was too late” — before globalization trampled their way of life.

A young Danish researcher named Jorn Dyerberg read the article with interest. So in 1970, he and another scientist, as later explained to Whole Foods Magazine, made the first of five expeditions to Greenland. The trips led to the finding that Inuit were substantially less susceptible to heart disease because of their unique diet, which consisted largely of seal and cold-water fish and few vegetables. Translation: Consumption of omega-3 fatty acids — fish oil — reduced the chance of developing CAD.

That striking conclusion in part helped spark what is today a $1.1 billion fish oil industry. Nutritional guidelines in Canada, the United States and Europe urge the weekly consumption of fish — preferably oily fish such as salmon — to prevent heart disease. Many foodies and nutritionists agree: Fish oil is good for you.

But what if the original study was flawed?

Last month, an article published in the Canadian Journal of Cardiology posited just that. The study, authored by four scientists led by George J. Fodor, alleged that the original research was not only deeply flawed but “very soft,” as Fodor told CBC News. The new study said Inuit communities are, in fact, afflicted with CAD just as frequently as non-Inuit communities. What’s more, Inuit, who have a life expectancy 10 years shorter than Danes, are particularly vulnerable to strokes.

“The alleged absence of CAD in Greenland Eskimos is a paradoxical finding, given that this is a population mainly sustained on a diet high in animal fat, absence of fruits and vegetables and other important nutrients,” the study said. (The study used the terms “Eskimo” and “Inuit” interchangeably.) “In other words, a diet which violates all principles of balanced and heart-healthy nutrition.” Then this: “Considering the dismal health status of Eskimos, it is remarkable that instead of labeling their diet as dangerous to health, a hypothesis has been construed that dietary intake of marine fats prevents CAD and reduces” clogged arteries.

The new findings do not discredit decades of research that show fish oil is part of a healthy diet. But they do raise questions about Dyerberg’s early research, which ultimately included analysis of blood fats, as well as the founding hypothesis of the fish oil industry.

At least nine studies referenced Dyerberg’s work in the last decade, Fodor found. And both Whole Foods and Omegold, a major producer of fish oil, have touted the original Greenland study. “Worldwide attention was first drawn to the amazing properties of the long chain omega-3 fatty acids when … two Danish researchers went to study the [Inuit] of Greenland,” claimed Omegold. “To their astonishment, [they] had a much lower incidence of cardiovascular disease.”

“Publications still referring to Bang and Dyerberg’s nutritional studies as proof that Eskimos have low prevalence of CAD represent either misinterpretation of the original findings or an example of confirmation bias,” Fodor’s study said.

The problem: Dyerberg’s research was conducted in Umanak, a town of 1,300 nestled 310 miles north of the Arctic Circle and 100 miles from the nearest hospital. “Although the studies of these two Danish investigators are routinely quoted in connection with the alleged low occurrence of CAD in Greenland Eskimos, the fact is that [they] did not examine the cardiovascular status of Greenland Eskimos or those living in and around the small community of Umanak.”

Instead, Fodor’s study said Dyerberg, who could not be immediately reached for comment, allegedly relied on state data which reported that CAD killed about 12 percent of Inuit. Those facts, however, were unreliable. Roughly 20 percent of death certificates were completed without a doctor. And if doctors were present, they had “limited diagnostic facilities.” Fodor said the Danish researchers’ “study population was widely scattered with few possibilities of communication…therefore, the reported data are likely an underestimation.”

Most striking: Other studies have found Inuit have a high risk of heart disease. One appeared in 1940. Another appeared in 2003, calling the scientific evidence “weak,” hinging on “uncertain mortality statistics.”

But despite those findings, the fish oil industry has continued to grow, as has research into its benefits. “To date,” the study concluded, “more than 5,000 papers have been published … not to mention the billion dollar industry producing and selling fish oil capsules [that are] based on a hypothesis that was questionable from the beginning.”

It’s unclear how the study will affect the industry or future research, but some across the world are already turning against fish oil.

On Thursday, news broke that a Chinese man named Feng Changshun was suing a Chinese fish oil producer — and its spokesman, former NBA star Yao Ming — for exaggerating the benefits of fish oil capsules. “I am angry because it has delayed my medical treatment,” he said. “It feels like I have been used as a lab mouse.”

Terrence McCoy covers poverty, inequality and social justice. He also writes about solutions to social problems.
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