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New study ties egg and cholesterol consumption to heightened risk of heart disease

(Reuters Health) – After a raft of studies reassuring consumers that eggs are OK to eat, a new report associates an increasing risk of heart disease with the increasing consumption of eggs.

The report, combining data from six earlier studies, found a 6 percent increased risk of cardiovascular disease when the average number of eggs consumed per day went up by half an egg.

“The take home message is that individuals who consume higher levels of dietary cholesterol are at increased risk for the development of heart disease and mortality later in life,” said study coauthor Norrina Allen, an associate professor of preventive medicine at Northwestern University’s Feinberg School of Medicine in Chicago. “And in the U.S. diet, eggs are one of the top sources of cholesterol.”

Still, Allen isn’t ready to tell everyone to go cold turkey on eggs.

“I’m not advocating people take them completely out of their diets,” she said. “I’m just suggesting that people eat them in moderation.”

It can be hard to translate the association between eggs and heart disease into advice, Allen allowed. That’s because we don’t all deal with cholesterol in the same way, she said. “The amount of cholesterol you consume isn’t linked in a straightforward way with the amount found in your blood,” Allen explained. “That depends on a lot of factors including your genes and how you metabolize cholesterol.”

Allen’s team analyzed data pooled from six studies involving a total of 29,615 people who were followed for a median of 17.5 years, according to the report in JAMA. At the start, participants filled in questionnaires detailing the foods they ate. They were not asked about their diets again.

Over time, there were 5,400 cardiovascular-related adverse outcomes, including 2,088 fatal and non-fatal heart disease events, 1,302 fatal and non-fatal stroke events, 1,897 fatal and non-fatal heart failure events and 113 other cardiovascular disease deaths.

When they analyzed the data, the researchers found an association between egg consumption as reported at the start of the study and participants’ risk of developing cardiovascular disease. As their egg consumption rose, so did their risk.

The association was weakened to the point that it was no longer statistically significant when researchers accounted for total cholesterol consumption. That, Allen said, means the association between eggs and heart disease is explained by the cholesterol in the eggs.

Other experts weren’t entirely convinced that the study shows that eggs were causing heart disease.

Cholesterol’s role in the development of heart disease has been discussed for more than three decades, said Dr. Dennis Bruemmer, a cardiologist with the Heart and Vascular Institute and an associate professor of medicine at the University of Pittsburgh Medical Center. “The particular contribution of cholesterol derived from eggs has also been studied in several studies, with varying and discrepant results,” Bruemmer said. “This study does have clear limitations, including self-reporting at a single time point. This limits its validity.”

While eggs contain quite a bit of cholesterol – about 200 mg, the maximum daily amount recommended in current guidelines – “eggs in moderation are probably acceptable from a nutritional standpoint,” Bruemmer said in an email. Moderation, he added, is “less than one egg a day on average, including eggs in foods such as bread.”

Dr. Holly Anderson agrees that the study has “real limitations.”

“It’s not good science,” said Anderson, a preventive cardiologist and director of education and outreach at the Ronald O. Perelman Heart Institute at the NewYork-Presbyterian/Weill Cornell Medical Center and an associate professor of clinical medicine at Weill Cornell Medicine.

A big issue for Anderson is that fact that a lot of the egg-eating participants also appeared to be consuming “large amounts of meats and processed meats,” she said. “If you’re consuming a huge amount of processed meats, it doesn’t matter how many eggs you’re eating.”

Moreover, Anderson said, the study is observational, which means it can only show there’s an association between egg consumption and heart disease but it can’t prove eggs are the culprit. It may just be that the people eating a lot of eggs are also consuming a lot of bacon, Anderson said.

That said, the study does have the strength of large numbers, Anderson said. “More than 29,500 patients is a lot and the follow-up of 17.5 years is also a lot,” she added. “That means we should at least be looking at the conclusions.”

SOURCE: JAMA, online March 15, 2019.

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