Cholesterol

Unscrambling the Data on Egg and Dietary Cholesterol Consumption

AUTHOR:
Michael J. Bloch, MD
Associate Professor, University of Nevada School of Medicine
Medical Director, Vascular Care, Renown Institute for Heart and Vascular Health
President, Blue Spruce Medical Consultants, PLLC
Reno, Nevada

CITATION:
Bloch MJ. Unscrambling the data on egg and dietary cholesterol consumption. Consultant360. Published online July 29, 2022.

 

Drawing a distinction between dietary cholesterol and blood cholesterol has always been difficult for patients and providers alike. Clearly-elevated levels of blood cholesterol carried on atherogenic lipid particles, like low-density lipoprotein (LDL), is a strong and independent risk factor for atherosclerotic cardiovascular (CV) events. But the data on dietary cholesterol generally, and egg consumption particularly, has always been murkier. Dietary cholesterol is absorbed in the small intestine where it is packaged along with dietary triglyceride into chylomicrons that are released into the bloodstream. In many ways, eggs are a nutritional superfood, packed with protein, low in sugar and carbohydrate, and abundant with vitamins and minerals. Eggs also have a favorable balance of unsaturated to saturated fat; however, a single hard-boiled egg contains about 180 mg of dietary cholesterol. Determining the net clinical value (or harm) of these nutritional components has been a matter of debate for decades.

The 2010 Dietary Guidelines For Americans recommended that healthy adults consume less than 300 mg of dietary cholesterol per day, which generally equates to less than 2 eggs.1 However, after an exhaustive review of the available evidence, the 2013 American Heart Association (AHA)/ American College of Cardiology (ACC) Guideline on Lifestyle Management to Reduce Cardiovascular Risk did not make a recommendation for reducing dietary cholesterol because the expert panel concluded that there was “insufficient evidence to determine whether lowering dietary cholesterol reduces LDL cholesterol.”2 And, the 2015 Dietary Guidelines Advisory Committee stated that “cholesterol intake need not be limited because there is only a weak relationship between cholesterol intake and serum cholesterol concentrations.”3 It should be noted that all of these recommendations were based on admittedly low-quality evidence, concentrated on the lipid effects rather than CV events, and fell short of emphasizing increased egg consumption as part of a healthy diet.

In this context, the recently published Alpha-Tocopherol, Beta-Carotene (ATBC) Cancer Prevention Study and updated meta-analysis provide a much clearer picture of the effect of dietary cholesterol and egg consumption on CV events and mortality, even if the resultant dietary recommendations will remain controversial. The ATBC analysis of more than 27,000 Finnish men demonstrated that greater dietary cholesterol and egg consumption was associated with modestly increased risk of CV events and total mortality.4 After correcting for other cardiovascular risk factors, each additional 300 mg per day of dietary cholesterol was associated with an approximately 10% increase in mortality risk and each additional 50-gram egg consumed each day increased CV risk and total mortality by 5 to 10%. In the included updated meta-analysis of more than 3 million participants, each additional egg consumed daily increased CV risk by 4% with a higher risk in US cohorts, intermediate risk in European cohorts, and minimal effect in Asian cohorts.

While the ATBC investigators made every attempt to account for other dietary components and traditional risk factors, untangling nutritional information from observational studies can be challenging. The apparent geographical heterogeneity of the findings from the meta-analysis suggests that perhaps there are other dietary patterns associated with egg consumption that may vary based on culture. For example, perhaps in the United States, egg consumption is a marker for increased saturated fat and simple carbohydrate intake with breakfast (eg, bacon and toast). And, the strongest data from ATBC is obviously limited by the inclusion of only Finnish men.

Finally, as Tobias points out in the editorial that accompanies the ATBC publication, the effect here appears modest compared with the data with other known adverse nutritional components.5 If people were to substitute egg and total cholesterol calories with healthier macronutrients like mono- and polyunsaturated fats and fiber the net effect would likely be positive. But if people substitute egg and total cholesterol calories with saturated fat or simple carbohydrate the net effect would likely be negative.

In conclusion, it appears that any focus on a single macronutrient in the diet misses the forest for the trees. While our patients should certainly not over-consume dietary cholesterol, in moderation, eggs can likely still be a part of an overall healthy eating pattern for most people.

  1. Dietary Guidelines for Americans 2010. US Department of Agriculture; US Department of Health and Human Services. December 2010. Accessed July 18, 2022. https://health.gov/sites/default/files/2020-01/DietaryGuidelines2010.pdf
  2. Eckel RH, Jakicic JM, Ard JD, et al; American College of Cardiology/American Heart Association Task Force on Practice Guidelines. 2013 AHA/ACC guideline on lifestyle management to reduce cardiovascular risk: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation. 2014;129(25 Suppl 2):S76-99. doi:10.1161/01.cir.0000437740.48606.d1
  3. Scientific report of the 2015 dietary guidelines advisory committee. US Department of Agriculture; US Departent of Health and Human Services. February 2015. Accessed July 18, 2022.  https://ods.od.nih.gov/pubs/2015_dgac_scientific_report.pdf
  4. Zhao B, Gan L, Graubard BI, Mannisto S, Albanes D, Huang J. Associations of dietary cholesterol, serum cholesterol, and egg consumption with overall and cause-specific mortality: systematic review and updated meta-analysis. Circulation. 2022;145:1506–1520. doi:10.1161/CIRCULATIONAHA.121.057642
  5. Tobias D. What eggsactly are we asking here: unscrambling the epidemiology of eggs, cholesterol and mortality. Circulation. 2022;145:1521-1523. doi:10.1161/CIRCULATIONAHA.122.059393