Are Eggs Healthy?

One of the most common question I receive during my lectures at medical conferences and on my social media posts is, "Are eggs healthy if you have heart disease?" Or is it safe to eat eggs?

Egg consumption and cardiovascular health have long been a topic of debate, with some studies suggesting that high levels of egg intake may increase the risk of heart disease, while others have found no association or even a protective effect.

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Research on Egg Consumption

Let's review the current evidence on the relationship between egg consumption and cardiovascular health, and discuss the potential mechanisms by which eggs may affect cardiovascular risk.

Generally speaking, eggs are a nutrient-dense food that are high in protein, vitamins, and minerals, and contain antioxidants such as lutein and zeaxanthin. However, eggs are also high in dietary cholesterol and even saturated fat, with one large egg containing about 186 mg of cholesterol and 1.6g of saturated fat. We used to believe that dietary cholesterol was the main determinant of cholesterol levels in the bloodstream, and that reducing dietary cholesterol intake was an important strategy for reducing the risk of cardiovascular disease.

Dietary Cholesterol Intake and CVD Risk?

Recent research has shown that the relationship between dietary cholesterol and blood cholesterol levels is complex and may be influenced by other factors such as the type of fats consumed and the presence of other nutrients in the diet.

We have since learned that dietary cholesterol matters in the extremes of consumption. If you are eating over 400mg and even up to 1000mg per day, then yes, your blood cholesterol will increase. but for the average American who consumes 200-300mg per day, dietary cholesterol does not affect circulating cholesterol very much.

The data on dietary cholesterol has gone back and forth, the latest research and data shows that high levels of cholesterol intake do in fact increase cardiovascular risk and mortality.

A meta analysis published in Circulation (the American Heart association's top peer reviewed journal) titled Associations of Dietary Cholesterol, Serum Cholesterol, and Egg Consumption With Overall and Cause-Specific Mortality: Systematic Review and Updated Meta-Analysis published in May of 2022 looking at 27,000 participants for 31 years, concluded that...

Conclusions: In this prospective cohort study and updated meta-analysis, greater dietary cholesterol and egg consumption were associated with increased risk of overall and CVD-related mortality. Our findings support restricted consumption of dietary cholesterol as a means to improve long-term health and longevity.

https://pubmed.ncbi.nlm.nih.gov/35360933/ 

As you can see above, as dietary cholesterol goes above 400mg daily and approaches 1000mg daily, you see increases in incidence of CVD and all cause mortality.

As you can see above, as the number of eggs increases, incident CVD and all cause mortality all increase. The lowest CVD and all cause mortality rates are 1 egg per day or less. 

For more from that research paper:

https://pubmed.ncbi.nlm.nih.gov/30874756/ 

Another large prospective cohort study, the Nurses' Health Study, followed over 117,000 women for up to 14 years and found no association between egg intake and the risk of coronary heart disease or stroke.

Similarly, a meta-analysis of 17 studies comprising over 250,000 participants found no association between egg intake and the risk of coronary heart disease, stroke, or total cardiovascular disease. Great news, right?

Are Eggs Protective and Healthy?

Other studies have even suggested that egg intake may have a protective effect on cardiovascular health. A review of 12 studies found that high egg intake was associated with a lower risk of stroke, and another study found that moderate egg intake (up to one egg per day) was associated with a reduced risk of coronary heart disease in people with type 2 diabetes.

It is important to note that these studies were observational in nature, meaning they cannot establish cause and effect. It is possible that other factors, such as the overall quality of the diet or other lifestyle factors, may be responsible for the observed associations. However, these findings do suggest that the relationship between egg intake and cardiovascular disease risk is more complex than previously thought and may not be solely determined by dietary cholesterol intake.

One egg per day, can be protective: https://pubmed.ncbi.nlm.nih.gov/27710205/  

Other Factors That May Play a Role in the Health Effects of Eggs

One potential explanation for the apparent lack of association between egg intake and cardiovascular disease risk is the fact that the effect of dietary cholesterol on blood cholesterol levels may be modulated by other nutrients in the diet, such as saturated and unsaturated fats and fiber. For example, a high intake of saturated fats, which are found in animal products such as meat and dairy, may increase LDL cholesterol levels and contribute to the risk of cardiovascular disease. On the other hand, unsaturated fats, which are found in plant-based oils and nuts, may have a protective effect on cardiovascular health. Similarly, a high intake of fiber, which is found in whole grains, fruits, and vegetables, may help to lower LDL cholesterol levels and reduce the risk of cardiovascular disease.

A study in the Journal of the American Medical Association from March 2019 titled, Associations of Dietary Cholesterol or Egg Consumption With Incident Cardiovascular Disease and Mortality looked at almost 30,000 participants and followed them for 13 years. They concluded... 

Conclusions and relevance: Among US adults, higher consumption of dietary cholesterol or eggs was significantly associated with higher risk of incident CVD and all-cause mortality in a dose-response manner. These results should be considered in the development of dietary guidelines and updates.

https://pubmed.ncbi.nlm.nih.gov/30874756/ 

To Egg or Not To Egg?

As you can see the data goes back and forth. Some studies showed benefit and even protective effects, while others showed some increased risk.

What I normally tell my patient is that the relationship between egg consumption and cardiovascular health is complex and remains the subject of ongoing research. We may not ever have a final and definitive answer. 

It's still important to consider the overall quality of the diet and the impact of other nutrients on cardiovascular health, especially saturated fat intake. The current evidence suggests that moderate egg intake, as part of a balanced diet, is not associated with an increased risk of cardiovascular disease.

Interestingly, studies have also shown that substituting whole eggs for egg whites or egg substitutes did show a reduction in mortality.

If you have significant risk factors and or a history of heart disease, you may want to consider limiting egg intake to 1 per day based on other studies and the totality data.

As with any dietary decisions, it is important to speak with your doctor, cardiologist or registered dietitian for personalized nutrition advice.

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