Recent research on the dangers of egg consumption is misleading and unnecessarily alarming. The dangers of cholesterol are over-hyped, and we can't underestimate the value of unprocessed, high-mineral foods.ella novak/Flickr
What is the most heart-healthy diet? The answer to this much-debated question just became more controversial after a study in the forthcoming issue of Atherosclerosis reported that egg yolks are nearly as bad for your arteries as cigarette smoke. After years relegated to the do-not-eat list for fear of cholesterol-raising effects, the humble egg was finally making its way back into mainstream acceptance as a heart-healthy food full of healthy fats and protein. But it appears this latest study may indeed send us back to the days of egg-white omelets and Egg Beaters.
The study's authors surveyed more than 1,200 men and women, with an average age of 61.5, who were attending vascular prevention clinics. The author's claim that regular consumption of egg yolks is about two-thirds as bad as smoking when it comes to increased build-up of carotid plaque, a risk factor for stroke and heart attack.
But many believe there are issues with this study's methodology as well as the way the authors drew their conclusion. First, the study was based on recall questionnaires, which are notoriously unreliable. More importantly, the authors singled out one food from the patients' diets and determined this caused the trend towards atherosclerosis. They could have picked another food at random -- say the toast eaten with the eggs -- and drawn an associative relationship between toast and atherosclerosis.
"I think it's dangerous to look at just one food and deduce that the trend you see is caused by that food," MIT researcher and senior scientist Stephanie Seneff wrote to me in an email regarding the study.
Dr. Frank Hu, professor of nutrition and epidemiology at the Harvard School of Public Health, also wrote to me in an email, "[The study] did not measure or control other aspects of diet such as intakes of meats, fruits, or vegetables and did not control for lifestyle factors such as physical inactivity. The data could be useful for generating some hypotheses, but it is difficult to draw any causal conclusions."
Despite these flaws, the damage to the reputation of egg yolks may already be done. "It's very worrisome that these authors of the egg-yolk-is-bad article have managed to come up with a fairly simple and relatively compelling story which will scare a lot of people away from eating egg yolks," Seneff said.
The study has potentially serious consequences for people trying to improve their health and reduce their risk of stroke and heart disease -- and that's because most people should be eating more eggs, and particularly the yolks, not fewer. That's what Seneff told me in a recent phone interview. She and her team at MIT are working on some compelling new research about the role of dietary fat and cholesterol and our health. Her research is so counter to the current dietary dogma that it sounds shocking at first: Seneff believes that Americans are actually suffering from a cholesterol deficiency rather than excess. She's concerned that studies like these only serve to confuse the public more about the role of dietary cholesterol. Seneff believes that cholesterol has been wrongly vilified and in fact, foods that contain high amounts of cholesterol -- like egg yolks and other animal proteins -- are key to improving heart health, maintaining a healthy weight, and staving off many diet-related diseases.
Of course, not everyone agrees. There are conflicting studies to show that dietary cholesterol both does and does not affect our blood levels of cholesterol. "Much of the cholesterol in the blood is produced endogenously," Hu wrote. "However, dietary factors (fats and cholesterol) can influence serum cholesterol levels." An article about eggs on the Harvard School of Public Health's website reads, "While it's true that egg yolks have a lot of cholesterol -- and so may weakly affect blood cholesterol levels -- eggs also contain nutrients that may help lower the risk for heart disease, including protein, vitamins B12 and D, riboflavin, and folate."
The picture becomes even more complicated because elevated cholesterol levels do not necessarily mean one is at greater risk for a heart attack. More than 60 percent of all heart attacks occur in people with normal cholesterol levels and the majority of people with high cholesterol never suffer heart attacks. Many studies now show that high LDL (the so-called "bad cholesterol") and heart disease are not linked. In 2005, the Journal of American Physicians and Surgeons reported that as many as half of the people who have heart disease have normal or desirable levels of LDL. Also in 2005, researchers found that older men and women with high LDL live longer.
Dr. J. David Spence, the first author of the egg yolk study and professor of neurology and clinical pharmacology at Western University, told me in an interview that serum cholesterol is "not the be all, end all of vascular risk." He's more concerned about what happens to our cholesterol levels after we consume cholesterol-containing foods, rather than our fasting cholesterol levels, which is what's checked at the doctor's office. "Egg yolks only raise fasting cholesterol by about ten percent," he said. "But four hours after you eat a high cholesterol meal you get inflammation in the arteries, there's increased oxidative stress, the increase in oxidized LDL cholesterol--which is the most harmful form or cholesterol -- is almost 40 percent, and you have impairment of the function of the artery lining."