"Eggs, especially the yolk, are a major source of dietary cholesterol," wrote Victor Zhong, lead author and a postdoctoral fellow in the Department of Preventive Medicine at Northwestern University Feinberg School of Medicine in Chicago. In a study published Friday in the medical journal JAMA, he and his colleagues noted that a single large egg contains about 186 mg of cholesterol.
The researchers studied the data from six US study groups including 29,000 people and followed by 17 years on average. Over the period of their follow-up, around 5,400 cardiovascular events happened, including 1,897 incidents of fatal and nonfatal heart failure, 1,302 fatal and nonfatal strokes, and 113 other heart disease deaths. An additional 6,132 participants died of other causes.
Consuming 300 mg dietary cholesterol per day was linked with a 3.2% higher risk of heart disease and a 4.4% higher risk of early death, Zhong's study of the data showed. And each additional half an egg consumed per day was associated with a 1.1% higher risk of cardiovascular disease and 1.9% higher risk of early death due to any cause.
A suspected reason for inconsistent results in the past was the fact that other data did not take into account that eating eggs may be related to other unhealthy behaviors, such as smoking, drinking, low physical activity, and an unhealthy diet. Also, cholesterol-containing foods are usually rich in saturated fat and animal protein.
"In contrast, the current study included a comprehensive assessment of these factors," wrote Zhong and his co-authors.
Dr. Robert H. Eckel from the University of Colorado School of Medicine wrote that this topic is important to health professionals and the public.
"The association of egg consumption and dietary cholesterol with [cardiovascular disease], although debated for decades, has more recently been thought to be less important," wrote Eckel, who was not involved in the research. 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," he wrote.
Victoria Taylor, a senior dietitian with the British Heart Foundation, told Science Media Centre that "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.
"Eggs are a nutritious food and, while this study focuses on the amount we're eating, it's just as important to pay attention to how the eggs are cooked and to the trimmings that come with them," said Taylor, who was not involved in the research. "Eating healthily is all about balance."
