Over the years, nutritional advice has flip-flopped on eggs, reflecting the current research at the time. On one hand, eggs have been vilified and linked to heart disease, yet they’ve also been touted as an integral part of a balanced diet—with some research suggesting that they may actually be beneficial for heart health.
Some nutritionists like to point out that eggs on their own are not as bad you think, as long as you skip the fatty bacon on the side. Others point to eggs as a fairly healthy form of protein that can help build muscle and even improve immune function.
Recently, however, several studies have again linked egg consumption to outcomes like diabetes and cardiovascular disease. Here’s what current research says about egg consumption.
Cardiovascular and cancer mortality
As noted in a February PLOS Medicine study, the link between egg consumption and cardiovascular disease has long been debated. While many studies have been published, evidence on the health benefits—and drawbacks—of eggs remains limited and inconclusive. This is partially due to small sample sizes and data that included very few deaths. Conclusions have often been skewed by confounding factors, like unhealthy lifestyle habits (including smoking and inadequate physical activity), or by the fact that cholesterol intake from eggs typically coincides with saturated fat consumption and other sources of cholesterol.
As such, authors of the PLOS Medicine study looked at cohort data from more than half a million Americans during a 16-year follow-up period and analyzed associations with more than 129,000 deaths. Participants were monitored for their intake of whole eggs, egg whites/egg substitutes, and cholesterol, via validated food frequency questionnaires.
Researchers found that both the consumption of whole eggs and cholesterol intake were positively associated with all-cause mortality, as well as cardiovascular disease and cancer mortality.
In fact, they concluded that for every additional 300 mg of dietary cholesterol consumed per day, the risk of all-cause, cardiovascular disease, and cancer mortality increased by 19%, 16%, and 24%, respectively. Given that a whole egg contains roughly 186 mg of cholesterol, this means eating two eggs each day could be increasing your likelihood of mortality from these causes. Researchers concluded that cholesterol from whole egg consumption contributed to more than 60% of both all-cause and cardiovascular disease deaths in the study.
On the other hand, findings indicate that those who consumed egg whites or egg substitutes had a lower all-cause mortality, as well as mortality from stroke, cancer, respiratory disease, and Alzheimer disease.
These findings corroborate a recent study, which examined a cohort of 29,615 Americans, and found that each additional daily intake of half an egg was associated with a 6%-8% higher risk of incident cardiovascular disease. Findings regarding the association between egg consumption and higher rates of cancer mortality were also aligned with studies in which dietary cholesterol was linked with increased incidence of breast and pancreatic cancers, while egg consumption was associated with a higher incidence of ovarian cancers.
According to the authors, the primary element driving these associations is cholesterol intake. While the association between whole-egg consumption and higher all-cause mortality remained significant after adjusting for demographic and dietary factors, it wasn’t significant after further adjustment for cholesterol.
The authors recommended replacing whole eggs with egg whites or an alternative protein source to protect cardiovascular health and increase longevity. “Our results should be considered by clinicians and policy makers in updating dietary guidelines for Americans,” the authors concluded.
Eggs and diabetes
The above study also suggests that whole egg consumption and cholesterol intake were associated with increased risk of diabetes mortality. Authors found that eating more than three eggs a week brought a higher risk of developing diabetes, a link supported by the findings of two additional studies published this year.
The first is a study published in Clinical Nutrition in March, which examined eating habits and health outcomes among nine cohorts totaling 103,811 Americans. Researchers aimed to discern whether past studies, which found a relation between egg consumption and type 2 diabetes, had been confounded by incidental dietary habits.
The median egg consumption among subjects was one egg per week, which researchers observed was not associated with an increased risk of diabetes. However, they found those who consumed two or more eggs per week did have an elevated risk of developing the disease, after adjusting for age, ethnicity, body mass index, exercise, smoking, alcohol intake, and other dietary patterns. In fact, compared with those who consumed no eggs, those who ate seven or more per week increased their risk of diabetes by 27%.
The second study, published in The American Journal of Clinical Nutrition in April, explored associations between egg consumption, cholesterol, choline, and betaine, and the risk of diabetes among elderly American women. Researchers looked at data from 46,263 women over a period of 13 years, during which 5,480 incident diabetes cases were diagnosed.
For those eating at least three eggs a week, there was a “steady increase in diabetes risk that may have been due to the cholesterol in the eggs.” However, they concluded that obesity was a far greater risk factor.
For now, go easy on the eggs
While eggs are a great source of protein, as well as vitamins and bioactive nutrients like lecithins and carotenoids, recent evidence suggests that you should pay attention to how much cholesterol you’re consuming. Having scrambled eggs occasionally may not do much harm, but if they’re a daily staple, you might want to look for an alternative source of protein, or just stick to the whites.