Are eggs going to kill you?

If you have been paying attention to the media, you might have heard that eggs increase the risk of cardiovascular disease. News outlets have been reporting on the recently published paper Associations of Dietary Cholesterol or Egg Consumption With Incident Cardiovascular Disease and Mortality (1). But is it true? Are eggs going to kill you?

Source of data

Researchers looked at data from 6 US cohorts:

1. Atherosclerosis Risk in Communities (ARIC) Study, 1989
2. Coronary Artery Risk Development in Young Adults (CARDIA) Study, 1988
3. Framingham Heart Study (FHS) Study, 2013
4. Framingham Offspring Study (FOS) Study, 1975
5. Jackson Heart Study (JHS), 2005
6. Multi-Ethnic Study of Atherosclerosis (MESA), 2002

As you can expect, sources of data differed across studies. Some were food frequency questionnaires (FFQ), in which participants indicate how often they ate amount X of food Y in the past year in 5/6 studies. The other study used a diet history for the past 28 days. It is good to note that FFQ can be highly unreliable.

Participants demographics

Out of the 29615 participants (again, all from the US), 31% were black. The mean age was 51.6 at the start of each study. The authors of the paper acknowledge results should not be extrapolated to non-US populations.

Food analysis

Due to the heterogeneity of data that was collected across the studies, the authors crunched some numbers to standardise food intake. Most importantly, they considered the ingredients in mixed dishes in their analysis. Therefore, all dishes containing eggs (including bacon and egg rolls, cake, pancakes, etc.) count toward egg intake for the purposes of this study.

Confounders

Participants who consumed eggs tended to be less physically active, smoke, and have unhealthy dietary patters. Researchers adjusted for variables that could affect results. However, they admitted residual confounding was likely.

Association does not mean causation

This should be the first thing that pops in your head when you read an observational paper. Researchers acknowledged this in their limitations section.

Other studies on eggs and heart health

Other studies that have looked at UK and US cohorts. For example, have not found associations between frequent egg intake and risk of conditions such as cardiovascular disease and stroke (2, 3, 4, 5).

Are eggs going to kill you?

Eggs have gone from being good to bad to good to bad in the past few decades and the jury is still out. Perhaps this indicates that we should not look at individual foods nor nutrients as heroes or villains but rather assess diet + lifestyle patterns as a package. In my opinion, the consumption of a diet based on whole foods alongside regular physical activity, proper sleep and stress management is unlikely to be life threatening. Having said that, people who have a genetic tendency to have elevated cholesterol upon consumption of dietary cholesterol (about 25% of the population) should watch their intake of cholesterol containing foods, including eggs (5).

References

1. Zhong VW, Van Horn L, Cornelis MC, Wilkins JT, Ning H, Carnethon MR, et al. Associations of Dietary Cholesterol or Egg Consumption With Incident Cardiovascular Disease and Mortality. JAMA. 2019;321(11):1081-95.
2. Guo J, Hobbs DA, Cockcroft JR, Elwood PC, Pickering JE, Lovegrove JA, et al. Association between egg consumption and cardiovascular disease events, diabetes and all-cause mortality. European Journal of Nutrition. 2018;57(8):2943-52.
3. Qureshi AI, Suri FK, Ahmed S, Nasar A, Divani AA, Kirmani JF. Regular egg consumption does not increase the risk of stroke and cardiovascular diseases. Medical science monitor : international medical journal of experimental and clinical research. 2007;13(1):Cr1-8.
4. Scrafford CG, Tran NL, Barraj LM, Mink PJ. Egg consumption and CHD and stroke mortality: a prospective study of US adults. Public Health Nutrition. 2010;14(2):261-70.
5. Clayton ZS, Fusco E, Kern M. Egg consumption and heart health: A review. Nutrition. 2017;37:79-85.

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