Do eggs cause high cholesterol?

A large egg contains about 186 mg of cholesterol.¹ Eggs are also high in protein and do not contain saturated fats unlike other sources of protein such as meat and dairy products, which also contain dietary cholesterol. Dietary cholesterol is found in foods of animal origin and is absent in foods of plant origin. The consumption of dietary cholesterol can result in increased body lipid levels. As a source of dietary cholesterol, eggs present a potential mode of serum cholesterol concentration elevation and hypercholesterolemia induction.² This is a concern because severe hypercholesterolemia is a major risk factor for the development of cardiovascular disease (CVD) which is the leading cause of death for people in the United States accounting for about 665,000 deaths per year, or 1 in 4 deaths.^3-5 Severe hypercholesterolemia is defined as serum low-density lipoprotein cholesterol (LDL-C) of 190 mg/dL or higher.^6,7 However a 2019 Science Advisory from the American Heart Association concluded after a review of all the published literature that dietary cholesterol and specifically eggs do not pose a significantly increased CVD risk.⁸ Likewise the Dietary Guidelines for Americans, 2015-2020, include eggs as an acceptable source of protein in a healthy diet that is high in fruits, vegetables, and moderate in whole grains, lean meats, and eggs.⁹

The authors of the science advisory reviewed all current and recent guidelines for a healthy diet, the management of cholesterol, and the prevention of CVD.⁸ They also reviewed 17 prospective cohort studies that investigated the relationship between dietary cholesterol and CVD risk and concluded that the majority of observational studies found no significant association between dietary cholesterol and increased CVD risk. The authors also analyzed egg intake and CVD risk identifying 20 observational studies (range of participants from 382 – 80,000 with most in the thousands) that met their criteria for inclusion. The studies mostly compared an egg intake of ≥7 per week versus ≤1 per week. Generally, no significant association between egg consumption and stroke or coronary heart disease (CHD) was found. However, two studies of a subpopulation of people, those with type 2 diabetes, found an increased CHD risk with egg consumption while another study of this population did not find an increased risk. Also, 3 cohort studies found that >1 egg per day intake versus less egg intake was related to an increased risk of heart failure of 20% to 30% in men, but not in women.

A 2017 systematic review of 28 published randomized controlled trials (27 of which were included in the meta-analysis) investigated the quantitative effect of egg consumption on serum lipid concentrations in 1734 participants.² The meta-analysis found that egg consumption resulted in increased TC by 5.60 mg/dL (95% confidence interval [CI] [3.11 – 8.09], p<0.0001), LDL-C by 5.55 mg/dL (95% CI [3.14 – 7.69], p<0.0001), and HDL-C by 2.13 mg/dL (95% CI [1.10 – 3.16], p<0.0001) compared with the control group. The rise in TC and LDL-C levels due to egg consumption appears to be smaller than the increase caused by other modifiable lifestyle CVD risk factors, such as poor diet, minimal exercise, smoking, and alcohol intake.^2,10  Barraj et al. determined that for most US adults age 25 and older, consumption of one egg daily results in less than 1% of CHD risk (population attributable risk [PAR] 0.1%, 95% CI [0.03% – 1.1%]) for those with none of the other modifiable risk factors.¹⁰ They found that adding one or more of the other modifiable risk factors raises risk significantly. For example, one egg a day and smoking result in a PAR of 9.1% (95% CI [9% – 1.4%]) and one egg a day, poor diet, inactivity, and being overweight result in a PAR of 14.95% (95% CI [14.6% – 18.5%]). This suggests that, although egg consumption increases cholesterol levels, it only adds a minimally small amount to the risk of developing CVD. In fact, in the 2017 meta-analysis study’s meta-regression, a positive dose-response was found between egg consumption and the rise in HDL-C, but none of the other lipid parameters.²

A 2013 systematic literature review of 16 studies identified 22 independent prospective cohorts with 1,600 to 90,735 participants and with follow-up times between 5.8 to 20 years.¹¹ A meta-analysis of the impacts of egg consumption and risk of CVD, cardiac mortality, and type 2 diabetes was performed. This study concluded that regular egg consumption does not increase CVD risk and mortality in the general population.

Conversely, the most recent observational study to address eggs, dietary cholesterol and incident cardiovascular disease and mortality came to a different conclusion.¹² They followed 29,615 participants for a median of 17.5 years. Unlike prior studies, each of these patients was analyzed on an individual level for quality of dietary intake including cholesterol from all types of foods. They found that each additional 300 mg of dietary cholesterol consumed per day was associated with a higher risk of incident cardiovascular disease (hazard ratio [HR] 1.17) and all-cause mortality (HR 1.18), and each additional ½ egg consumed per day was also associated with a higher risk of incident cardiovascular disease (HR 1.06) and all-cause mortality (HR 1.08). The researchers concluded that the dietary intake of cholesterol from eggs or other sources was linked to both increased serum cholesterol levels and worse cardiovascular outcomes in a dose-dependent manner. This is especially true in the context of the current US diet which consists of too much caloric intake.

Despite this new data being somewhat at odds with recent dietary guidelines, all experts recommend an overall heart-healthy diet, such as a Mediterranean diet or the DASH diet,  rather than solely eliminating individual foods as the best approach to lowering cholesterol and CVD prevention.^1,3,6-9 Being mindful about eating less than ½ egg per day may be prudent if you consume other forms of dietary cholesterol or are told by your doctor that you have high serum cholesterol or are at higher risk for cardiovascular disease.

^References

1. US Department of Agriculture ARS, Laboratory ND. USDA National Nutrient Database for Standard Reference, Legacy. Version Current: April 2018. 2018.
2. Rouhani MH, Rashidi-Pourfard N, Salehi-Abargouei A, et al. Effects of egg consumption on blood lipids: a systematic review and meta-analysis of randomized clinical trials. J Am Coll Nutr 2018; 37 (2): 99-110.
3. Arnett DK, Blumenthal RS, Albert MA, et al. 2019 ACC/AHA guideline on the primary prevention of cardiovascular disease: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Circulation 2019; 140 (11): e596-e646.
4. Weir HK, Anderson RN, Coleman King SM, et al. Heart disease and cancer deaths — trends and projections in the United States, 1969–2020. Prev Chronic Dis 2016; 13 (160211).
5. Virani SS, Alonso A, Benjamin EJ, et al. Heart disease and stroke statistics-2020 update: a report from the American Heart Association. Circulation 2020; 141 (9): e139-e596.
6. Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the management of blood cholesterol. Circulation 2018: Cir0000000000000625.
7. Bibbins-Domingo K, Grossman DC, Curry SJ, et al. Statin use for the primary prevention of cardiovascular disease in adults: US Preventive Services Task Force recommendation statement. JAMA 2016; 316 (19): 1997-2007.
8. Carson JAS, Lichtenstein AH, Anderson CAM, et al. Dietary cholesterol and cardiovascular risk: a science advisory from the American Heart Association. Circulation 2020; 141 (3): e39-e53.
9. 2015 – 2020 dietary guidelines for Americans. 8 ed: U.S. Department of Health and Human Services and U.S. Department of Agriculture; 2015.
10. Barraj L, Tran N, Mink P. A comparison of egg consumption with other modifiable coronary heart disease lifestyle risk factors: a relative risk apportionment study. Risk Anal 2009; 29 (3): 401-415.
11. Shin JY, Xun P, Nakamura Y, et al. Egg consumption in relation to risk of cardiovascular disease and diabetes: a systematic review and meta-analysis. Am J Clin Nutr 2013; 98 (1): 146-159.
12. Zhong VW, Van Horn L, Cornelis MC, et al. Associations of dietary cholesterol or egg consumption with incident cardiovascular disease and mortality. JAMA 2019; 321 (11): 1081-1095.