The research on eggs over the years has been confusing, to say the least. One year, they’re “bad” because they contribute to dietary cholesterol, which has been associated with greater risk of cardiovascular disease (CVD). But then, the next year they’re back on the sunny side of the plate when researchers determine the link between egg intake and CVD to be insignificant. So, which is it? Environmental Nutrition cracks open the latest research to help you decide.
“While it might appear otherwise, the science around eggs actually has not been oscillating year-in, year-out,” says Jen Houchins, PhD, RD, director of nutrition research for the American Egg Board‘s Egg Nutrition Center. “It just looks that way when the media focuses on any one study in isolation — good or bad. The truth is that science doesn’t change all that quickly, especially nutrition science,” says Houchins. So, only when the total scientific literature is considered, which encompasses years of research, can consensus occur.
Houchins uses the example of the update in the recommendation from the Dietary Guidelines for Americans from its 2010 to its 2015 edition. The 2010 edition advised that we limit consumption of dietary cholesterol to 300 milligrams per day, but this was not included in the 2015 edition based on evidence from 16 studies over many years that showed no significant relationship between consumption of dietary cholesterol and serum cholesterol.
The latest research
As research continues, the goal of the findings is consensus. But the findings are sometimes contradictory. For example, a study published in the March 2019 JAMA found that higher cholesterol and egg consumption were associated with increased risk of CVD and death, reporting that an additional 300 milligrams of cholesterol raised this risk, as well as eating an average of three to four eggs per week. This was an observational study, however, which means that the study did not actually prove that eating eggs caused an increased risk of CVD. And, researchers reported that the higher risks were mostly from overall dietary cholesterol, which came mostly from meat sources and only modestly from eggs.
However, nearly a year later, a study, published in the January issue of The American Journal of Clinical Nutrition, found no significant associations between egg consumption and risk of CVD or death, even among people with a history of CVD or diabetes. Researchers based these findings on three international prospective studies that included about 177,000 individuals from 50 countries in six continents. “Of significant interest, this study is unique in that it evaluated participants that did not have a history of CVD and also included participants with a history of coronary, peripheral, or cerebrovascular disease,” says Houchins.
The whole egg
Another study suggests that consuming eggs as part of a healthy eating pattern may even benefit the heart. The study, published in the June 2019 issue of The American Journal of Clinical Nutrition, evaluated the effects of breakfast meals containing either two whole eggs or egg whites on postmenopausal women (they are at greater risk for CVD than younger women). No significant change occurred in cholesterol levels among those who ate whole eggs compared to those eating egg whites. Yet, there was an improvement in the function of HDL, or “good” cholesterol, in those who ate whole eggs.
This study might suggest that eggs, like any whole food, are more than just the sum of its parts. There is a synergistic effect, meaning that the ingredients work together differently and even better than if they were isolated. Eggs are a good source of protein, and they provide eight essential nutrients: protein, riboflavin, vitamin B12, biotin, pantothenic acid, iodine, selenium, and choline. And they also contain about 180 milligrams of cholesterol. Yet, the overall effect of eating whole eggs was positive, improving the function of “good” cholesterol in the body.
Currently, eggs are a part of all three healthy dietary patterns recommended in the 2015-2020 Dietary Guidelines for Americans, and the American Heart Association Nutrition (AHA) Committee, in its most recent science advisory on dietary cholesterol and cardiovascular health published in the January 2020 journal Circulation, says eggs may be included as part of healthy eating patterns. Within the recommended Mediterranean-style and DASH (Dietary Approaches to Stop Hypertension)-style diets, the AHA says healthy individuals can consume up to one whole egg daily and older healthy individuals, due to the nutritional benefits and convenience of eggs, may consume up to two eggs per day. In addition, vegetarians, because they eat more plant-based proteins rather than meats, which contain cholesterol, may eat more eggs within the context of moderation.
The bottom line
As with any research, it’s important to consider each egg study on its own, including both merits and limitations. But, as Houchins says, it’s the overall context of the science that will reveal the truest takeaway. In the case of eggs, the science demonstrates that eating eggs is not associated with CVD. So, go ahead and enjoy them in moderation within a healthy diet.