Egg Study Not All It’s Cracked Up To Be

Aug 16, 2012 8:00am
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A new study says eggs may be on par with cigarettes when it comes to heart health, but doctors and media critics say it’s not a fair comparison.

Researchers at Western University in Canada surveyed 1,200 patients about their egg and cigarette consumption and used ultrasound to measure the plaque in their arteries. They then concluded in the study, which was published in the journal Atherosclerosis, that people who ate more eggs over time had more plaque in their arteries, and equated eating eggs to smoking cigarettes.

The study’s lead researcher, Dr. David Spence, said in a press release that his study has shown that yolks make plaque build up more quickly in the arteries, “about two-thirds as much as smoking,” adding, “in the long haul, egg yolks are not okay for most Canadians.”

But cardiologists say the study shouldn’t be taken so seriously because the research is flawed.

“This is very poor quality research that should not influence patient’s dietary choices,” said Dr. Steven Nissen, who chairs the department of Cardiovascular Medicine at the Cleveland Clinic Foundation, in an email. “It is extremely important to understand the differences between ‘association’ and ‘causation’.”

Nissen said the researchers relied on patients to recall how many eggs they consumed, but asked them once and assumed it remained constant, which isn’t reliable. He said the way researchers measured patients’ plaque has come under “considerable criticism,” and that researchers failed to adjust for other dietary factors.

Dr. David Frid, a cardiologist at the Cleveland Clinic, told ABCNews.com he doesn’t think smoking should be equated with eating eggs because eggs have an indirect rather than direct impact on heart disease. The eggs have to first increase cholesterol to create plaque build-up. The impact of smoking on heart disease is direct because smoking causes arteries to become inflamed, which prompts the body to respond with plaque.

He said the study fails to take exercise or other dietary habits into account. Study participants could have consumed more salt, or they could have been on cholesterol-reducing drugs, too.

“It may be that people who consume a lot of eggs also consume a lot of other fatty foods,” Frid said, adding that how the egg is prepared should also be taken into account.

Dr. Jorge Plutzky, the Director of the Vascular Disease Program at Brigham and Women’s Hospital, said that the study authors explained the limitations of their study, which includes the potential for other variables to mask results and errors inherent in having patients self-report their egg consumption.

He said what the study really does is generate “a clue or suggestion” that needs to be revisited. It is not conclusive.

Still, the good headline potential was too tempting for several media outlets to ignore and the story ran widely, and in some cases without any comment from outside experts

Dr. Tom Linden, a medical journalism professor at the University of North Carolina,said journalists should exercise caution when writing about studies like this. He said they should put the studies into context by explaining the caveats and consulting experts.

“The danger here is headline writers who aren’t necessarily science writers may go way overboard in headlining the story,” Linden said.

Linden said his bottom line is that journalists and readers should be cautious when they interpret study results. Studies need to be put in context beyond the snappy headline or lead.

“They are interesting, they are provocative, but by no means are they the final word on this,” he said.

Dr. Richard Besser, the Chief Health and Medical Editor, of ABC News, spoke about the egg study on Good Morning America Wednesday morning.

“Eggs keep getting a bum rap,” Besser said. “First they’re really good for you, and then they’re bad for you, and this is another one where they’re bad for you.  But there are a number of things that affect your cholesterol that they didn’t look at that people can really pay attention to.”

Besser suggested exercising, reducing saturated fats, and maintaining a healthy weight. He said an egg a day is fine, unless you have heart disease, in which case limiting consumption to four eggs a week is a good idea.

“Eggs are a great source of balanced protein and many vitamins,” he said. “If you do it in moderation, it’s a great part of your diet.”

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