Did a study claim there’s no link between eggs and cholesterol? It might be biased

You’ve probably read at some point a news story or research claiming eggs don’t actually raise cholesterol levels. But those findings may have been biased because of faulty industry-funded research, according to a new review.

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A group of researchers from the Physicians Committee for Responsible Medicine looked at all the research studies from 1950 to March 2019 that assessed the effect of eggs on blood cholesterol levels. They studied funding sources and if they influenced the findings.

The results, published in the American Journal of Lifestyle Medicine, showed that before 1970 the industry didn’t have a role in cholesterol research. But industry-funded studies increased over time, from none in the 1950s to 60% in 2010-2019 — and industry-funded studies are well known to be associated with biases.

“In decades past, the egg industry played little or no role in cholesterol research, and the studies’ conclusions clearly showed that eggs raise cholesterol,” said study author Neal Barnard. “In recent years, the eggindustry has sought to neutralize eggs’ unhealthy image as a cholesterol-raising product by funding more studies and skewing the interpretation of the results.”

As a whole, more than 85% of the studies the researchers looked at, no matter if they were funded by the industry or not, found that eggs have negative effects on blood cholesterol. But those industry-funded downplayed the findings, the researchers claimed.

That means that when the data showed cholesterol levels increased because of egg consumption, the conclusions focused on something else. Almost half of the industry-funded studies had conclusions that didn’t match with the actual study results, compared to 13% of the non-industry funded studies.

For example, a 2014 study, associated the addition of two eggs at breakfast five days a week over 14 weeks to mean LDL cholesterol. Despite the results, the investigators said that an extra 400mg per day of dietary cholesterol didn’t affect blood lipids.

Such studies didn’t just cause misleading headlines, there have also been implications in policies. Back in 2015, the U.S. Dietary Guidelines Advisory Committee said that “available evidence shows no appreciable relationship between consumption of dietary cholesterol and serum cholesterol.”

Nevertheless, after looking at the evidence, the US government didn’t carry that statement forward in the final guidelines, which called for eating “as little dietary cholesterol as possible.”

“The egg industry has mounted an intense effort to try to show that eggs do not adversely affect blood cholesterol levels,” added Dr. Barnard. “For years, faulty studies on the effects of eggs on cholesterol have duped the press, public, and policymakers to serve industry interests.”

There have been many meta-analyses that concluded that egg consumption does raise cholesterol levels. A 2019 study showed that eating an egg each day raises low-density lipoprotein (LDL, or “bad”) cholesterol by about nine points. The study found that every 100 milligrams of added dietary cholesterol raised LDL cholesterol levels by about 4.5 mg/dL.

The report published in the American Journal of Lifestyle Medicine analyzed 153 studies, 139 of which showed eggs raise blood cholesterol — and not a single one of them reported a significant net drop in cholesterol concentrations associated with egg consumption.

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