The controversy over eating eggs and the impact they have on blood cholesterol, cardiovascular disease, and mortality have been raging since 1968. At that time, the American Heart Association recommended that people should consume no more than 300 mg of dietary cholesterol a day and no more than three whole eggs a week. Hu et al. published the first large, long-term study in 1999 that disputed current beliefs at that time of causation of cardiovascular disease and egg consumption, and several meta-analyses have confirmed the findings. When the Dietary Guidelines for Americans 2015-2020 was published in 2015, they dropped the dietary cholesterol and egg restrictions as had most health promotion agencies worldwide.
Today, the debate continues with the publication by Zhong et al. of their study in the Journal of the American Medical Association (JAMA). The authors sought to determine the "associations of dietary cholesterol or egg consumption with incident CVD and all-cause mortality." According to CNN, the researchers analyzed the data from six U.S. study cohorts that followed over 29,000 people for an average of 17½ years. During that time, there were a "total of 5,400 cardiovascular events with 1,302 fatal and nonfatal strokes, 1,897 incidents of fatal and nonfatal heart failure and 113 other heart disease deaths; an additional 6,132 participants died of other causes." The key takeaway point from this study was that, among U.S. adults, a "higher intake of dietary cholesterol or eggs was significantly associated with a higher risk of incident CVD and all-cause mortality in a dose-response manner."
Since previous studies did not consider that egg consumption may be related to other unhealthy behaviors including lack of physical activity, smoking, an unhealthy diet, and that cholesterol-containing foods are usually high in saturated fat, Zhou wrote that "In contrast, the current study included comprehensive assessment of these factors."
The CNN article quoted Richard Eckel, MD, from the University of Colorado School of Medicine, "The association of egg consumption and dietary cholesterol with [cardiovascular disease], although debated for decades, has more recently been thought to be less important." However, compared with previously published analyses, the new report "is far more comprehensive, with enough data to make a strong statement that eggs and overall dietary cholesterol intake remain important in affecting the risk of [cardiovascular disease], and more so the risk of all-cause mortality."
As stated by Victoria Taylor, a senior dietitian with the British Heart Foundation, "this type of study can only show an association, rather than cause and effect, and more research is needed for us to understand the reasons behind this link." Apparently, the debate over this topic is not over.