Prevailing health science regarding eggs recently became a bit more complicated, when a new report in the Journal of the American Medical Association linked the popular breakfast food with an increased risk of heart disease. These new findings contradict a 1999 study published in the same journal that showed no link between egg consumption and the risk of cardiovascular disease, a study that subverted the then-common theory posited in the 1970s that eggs did, in fact, cause heart disease.
The new research, conducted by scholars from Northwestern University's Feinberg School of Medicine, pooled the results of six studies covering nearly 30,000 participants. The researchers found that consuming three to four eggs per week was linked to a six percent higher risk of cardiovascular disease; consuming two eggs per day was associated with a 27 percent higher risk of heart disease.
The “take-home message” of the study, according to co-corresponding study author Norrina B. Allen Ph.D., is “really about cholesterol, which happens to be high in eggs and specifically yolks.”
"Our study," she says, "showed if two people had [the] exact same diet and the only difference in diet was eggs, then you could directly measure the effect of the egg consumption on heart disease."
Some experts note that observational studies such as these must be interpreted with caution, as they do not fully account for the effects of other behaviors that may be associated with eating more eggs. Increased consumption of breakfast meats like bacon and sausage, for example, has been associated with a greater risk of heart disease.
The study also does not account for possible changes in the participants' diets over time, as they were only asked about their diets once.
"We hope that in future studies we can look at how changes in diet over the long term may be impacting this risk for heart disease," Allen says.
Current American dietary guidelines impose no limit on daily egg consumption; until 2015, the limit was set to less than two large eggs per person, per day.
"I do think that guideline committees will have to take the evidence into account when they're trying to understand what a healthy — or a moderate — amount of cholesterol would be," Allen tells NPR.
According to the USDA, the average American consumes 280 eggs per year.
Heart disease is the leading cause of death in the United States, according to the Centers for Disease Control and Prevention.
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