Saturday, July 13, 2019

New research on eggs and cardiovascular disease

Eggs are back in the news in a big way after a meta-analysis published in April in the Journal of the American Medical Association showed an increased risk of cardiovascular disease with only ½ egg consumed per day. Should this study lead us to alter our consumption of eggs? Let’s take a closer look.

The Article
The meta-analysis included 29,615 participants from 6 prospective U.S. cohorts that were followed for roughly 18 years (Reference 1). Each additional half egg consumed per day was associated with a 6% higher risk of cardiovascular disease and an 8% higher risk of mortality.

Limitations And Other Research
While this is definitely an interesting study and we must consider the findings, there are two reasons not to go completely overboard and swear off eggs completely.

#1: There are some methodological issues with this study. To start with, only a single measure of egg consumption was taken and then subjects were followed for 18 years. There is a really good chance that egg consumption changed during this time. Very few of us eat the same way for 18 consecutive years. This study did not account for changes in diet over the follow-up.

Another methodological issue is that the control of confounders was not ideal. A confounder is a variable that may impact risk of cardiovascular disease. To deal with a confounder, you measure it and then control for it in statistical models. Similar to egg consumption, confounders in this study were not updated, just a baseline measure was used. This leaves the door open for residual confounding. Further, certain confounders were left out of the models, including family history of cardiovascular disease, menopausal status and supplement use.

#2: Other studies that were better executed do not show an increased risk of cardiovascular disease with a high consumption of eggs. For example, in an analysis of the Nurses’ Health Study and the Health Professional Follow-up Study that included 117,933 men and women, no significant association was found between consumption of one egg per day and risk of heart disease or stroke (Reference 2). In this study, both egg consumption and confounders were repeatedly updated during the follow-up period. There was also a more complete control of confounders.

Another very large meta-analysis was conducted a few years back (Reference 3). This analysis included subjects taken from 22 cohorts with a follow-up of up to 20 years. When comparing subjects who consumed one or more eggs per day to subjects consuming less than 1 egg per week, there was no increased risk of heart disease, stroke or total cardiovascular disease.

Conclusions And Recommendations
While the results of this new study need to be considered, a lot of other well-designed research has shown that eggs are safe to consume. If you are otherwise healthy, a moderate consumption of eggs can be considered part of a healthy diet. Keep in mind that eggs are a really good source of protein, healthy fat, vitamins and minerals. The yolks are very much like a multivitamin pill.

If you have diabetes, talk to your doctor about how many eggs you should consume, as some research has shown an increased risk of cardiovascular disease with high egg consumption in diabetics.

1) Zhong VW, et al. Association of dietary cholesterol or egg consumption with incident cardiovascular disease and mortality. Journal of the American Medical Association 2019; 321:1081-95.

2) Hu FB, et al. A prospective study of egg consumption and risk of cardiovascular disease in men and women. Journal of the American Medical Association 1999; 281:1387-94.

3) Shin, et al. Egg consumption in relation to risk of cardiovascular disease and diabetes: A systematic review and meta-analysis. American Journal of Clinical Nutrition 2013; 98:146-59.

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