For the past several decades, individuals with heart disease or at high risk for the development of heart disease have been advised to consume <200 mg/day of dietary cholesterol, whereas healthy adults are advised to consume <300 mg/day. Such recommendations are based on the assumption that dietary cholesterol produces harmful increases in blood cholesterol, which increases risk for developing atherosclerosis.
However, this simplistic thinking of A (i.e., dietary cholesterol) increases B (i.e., blood cholesterol) which increases C (i.e., heart disease risk) has been challenged in recent years as advances in diet and cardiovascular disease (CVD) research have revealed that the story is not that straight forward . We now know that there are other risk factors that influence heart disease risk potentially as much as or more so than elevated blood cholesterol (e.g., inflammation, vascular function, etc.). And with regards to blood cholesterol, not all types of “bad” cholesterol (LDL-cholesterol) may be atherogenic. Finally, dietary patterns may be more important for influencing CVD risk markers than isolated components, like dietary cholesterol. And dietary cholesterol may not adversely affect CVD risk factors to the same degree as was previously thought.
Consistent with this thinking is a recently published paper by Dr. David Katz from the Yale University School of Medicine. His laboratory evaluated 32 patients with documented coronary artery disease who consumed one of three daily breakfast treatments for 6 weeks each: 2 eggs/day; ½ cup of Egg Beaters/day; high-carbohydrate meals such as a bagel, waffles, pancakes, and cereal with milk. Each treatment period was separated by a 4-week washout.
A number of different cardiovascular risk markers were measured before and after each 6-week intervention period. Compared to the high-carbohydrate condition, 2 eggs/d did not adversely affect flow-mediated dilatation (an indicator of vascular function), blood cholesterol, blood pressure, or body weight. Further, there were no differences between the 2 egg/day and Egg Beaters conditions. This despite the fact that cholesterol intake was 742 mg/d in the egg group versus ~200 mg/d in the Egg Beaters and high-carbohydrate breakfast conditions.
This is the first clinical intervention study to evaluate the effects of cholesterol/egg intake on multiple cardiovascular risk markers, including endothelial function, in patients with diagnosed CVD. The investigators state in the paper that, “Excluding eggs from the diets of patients with CVD as per the AHA dietary recommendations could potentially lead to alternate choices high in starch and sugar, potentially associated with increased CVD morbidity and mortality.”
Although this study was small and relatively short in duration, the results certainly challenge the current thinking around cholesterol restrictions for those with CVD. As is always the case in nutrition science, additional research is needed to better understand the role of dietary cholesterol in disease risk and progression.