The idea that dietary cholesterol increases circulating cholesterol levels and the risk for coronary heart disease (CHD) has been a topic of heated debate for decades
This theory has been justified by early epidemiological studies that reported correlations between cholesterol intake and CHD and by feeding trials of short duration that showed dietary cholesterol to moderately increase circulating total and LDL cholesterol levels.
Until recent years, the American Heart Association and the Dietary Guidelines for America recommended that healthy adults limit dietary cholesterol intake to 300mg/day.
Recent evidence from epidemiological studies and meta-analyses, however, challenges the theory that dietary cholesterol contributes to CHD.
In light of this evidence, the 2015 Dietary Guidelines for America no longer recommend any limitation on dietary cholesterol, and reports from the American Heart Association in 2014 also make no recommendation to limit dietary cholesterol intake.
Eggs are a common source of dietary cholesterol, providing 186mg per egg. In a meta-analysis published in the November 2016 issue of the Journal of the American College of Nutrition, Alexander and colleagues analysed the evidence to date on the relationship between egg consumption and risk of CHD or stroke.
The meta-analysis included only prospective cohort studies of adult human populations that provided risk estimates for egg intake and cardiovascular outcomes, including CHD and stroke.
Seven studies (276,000 participants) evaluated stroke as an outcome, and seven studies (308,000 participants) evaluated CHD as an outcome.
The studies were conducted mostly in the United States but also in Japan, Australia, Spain, and the United Kingdom. Studies provided data from well-known cohort studies, including the Nurses Health Study, Health Professionals Follow-up Study, and Northern Manhattan Study. Follow-up periods ranged from 6 to 26 years.
Results comparing high egg consumption (approximately 1 egg/day) with low egg consumption (<2 eggs/week) showed no correlation with CHD risk but a statistically significant 12% reduction in stroke risk with high egg consumption.
There was no dose-response trend for reduced stroke risk with increasing egg intake. These results were consistent with the two other most recently published meta-analyses on the topic.
Eggs are a nutrient-dense food, providing protein, essential fatty acids, antioxidants, choline, vitamins and minerals. The authors of this meta-analysis conclude that consumption of one egg per day poses no increased risk for CHD and may protect against the risk of stroke.