March 15, 2019 -- Eggs, a staple of the American diet, have been cast once again as a villain. It’s not specifically the eggs, but the cholesterol in eggs that seems to be the problem, according to a new study.
Wait, what? Yes, it’s true. Even the researchers who worked on the study aren’t happy about it.
“It’s sad news to everyone,” says study author Norrina Allen, PhD, a cardiovascular epidemiologist at the Northwestern University School of Medicine in Chicago.
You might be forgiven for thinking of eggs as beyond reproach. In 2015, the experts who compile the U.S. Dietary Guidelines largely gave cholesterol a pass, saying there wasn’t enough evidence to support telling Americans to stick to a certain daily limit. WW (formerly Weight Watchers) doesn't require members to track or measure how many eggs they eat, counting them as a free food on its diet plan. As Americans have embraced low-carb diets, many have turned to eggs as a reliable protein source. According to industry data, the average American will eat more eggs in 2019 than any time for the past 20 years.
But a new study of studies is once again advising caution with cholesterol, and specifically eggs, which are a rich source of the waxy fat. The average egg contains 200 milligrams -- more cholesterol than is in most fast-food double cheeseburgers. Of course, cheeseburgers have many other dietary problems, including saturated fat and sodium.
Earlier versions of the dietary guidelines have advised Americans to keep their cholesterol under 300 milligrams daily.
Cardiologists say they realized that people are confused.
“The problem is that everybody is fixated on protein, and unfortunately Americans get a lot of saturated fat and cholesterol from animal sources of protein,” says Leslie Cho, MD, director of the women’s cardiovascular center at the Cleveland Clinic in Ohio.
“Here’s what we want to tell our patients: We’re sorry it’s so confusing. One day you have this news. Another day you have that news. It’s horrible, and I totally sympathize,” says Cho.
“The totality of evidence is pretty clear,” she says. “Eat mostly vegetables and try to limit the amount of saturated fat and dietary cholesterol,” including eggs and other products with animal fat, says Cho, who was not involved in the study. She said the new study did a good job of summing up the evidence.
The research is a new analysis of six previous studies that included nearly 30,000 Americans. Those studies all took written snapshots of participants’ diets and then followed them forward in time. In some cases, people in the studies were followed for between 10 and 30 years.
They found that eating just half an egg a day was linked to a 6%-8% increased risk of having a heart attack, stroke, or early death over the course of the study, compared to someone who didn’t eat eggs. What’s more, the more eggs a person ate, the more those risks increased. People in the study who averaged an egg every day saw their risk of a heart-related event such as a heart attack or stroke increase by 12% compared to someone who didn’t eat eggs. Those who averaged two eggs every day had a 24% increased risk of heart-related events.
Researchers saw similarly increased risks for people who ate processed and unprocessed red meat.
Bottom Line on Eggs Still Unclear
Those numbers sound big, but they are what’s known in science as relative risks. The researchers also looked at absolute risks -- the risk increase to a person over a given period of time. Absolute risks are what matter most when considering how a behavior or choice might influence your health. Over the course of these studies, eating just half an egg a day, or about three eggs a week, increased a person's risk of a heart attack, stroke or some other heart-related event by a small amount -- about 1%. It boosted a person’s risk of an early death by about 2%.
Those associations held even when researchers looked at the overall quality of a person’s diet. Those who included eggs as part of a healthy diet didn’t have lower risks compared to those who ate eggs alongside less nutritious foods.
Marion Nestle, PhD, is a professor of nutrition, food studies, and public health at New York University. She points out that those associations are “modest.”
“Is it clinically meaningful? Hard to know,” says Nestle, who was not involved in the study.
Nestle also points out that many of the studies considered for the 2015 dietary guidelines that exonerated dietary cholesterol as a risk for heart disease were funded by the egg industry.
Mickey Rubin, executive director of the American Egg Board’s Egg Nutrition Center, questioned the new study’s findings. While the findings are “interesting and point to the need for further research, Rubin said in a statement that the study is “inconsistent with multiple recent studies showing no association between eggs and heart disease risk.”
This new study, he noted, had nearly 30,000 participants. A previous meta-analysis of multiple studies had more than 350,000 participants and found no correlation between egg consumption and cardiovascular risk.
The new analysis is observational, which means that it can’t prove cause and effect. There could be other reasons people who ate more eggs had greater numbers of heart problems besides the eggs.
But the study was also carefully done. When researchers adjusted their results to account for the effects of cholesterol by itself, the association with heart disease and death went away, giving them confidence that it was the cholesterol, as opposed to something else in eggs, that was the link.
It follows a 2018 study that looked at the totality of evidence collected from 28 studies that had people eat eggs as an experiment and then looked at changes to their blood lipids. Overall, the study found eating eggs boosted total cholesterol by about 5 points compared to people who were on diets that didn’t include eggs. Most of that increase came from an increase in LDL, or “bad” cholesterol.
Even though today’s news may be jarring, nutritionists say you don’t have to give up on eggs completely if they’re a regular part of your diet.
“While scientists are sorting all of this out, an egg now and then does not seem unreasonable,” Nestle says. “As with everything else in nutrition, variety, unprocessed and moderation are strategies that work pretty well.”
The study authors agree.
“In this case, what we’re really talking about is just the cholesterol component of eggs, so the egg yolks,” Allen says.
“But there are other parts of the eggs. There are amino acids and there’s choline, and those might have a benefit. So we’re not suggesting eliminating eggs from your diet. But we do recommend that people do consider them in moderation,” she says.
One healthier substitution might be replacing whole eggs with egg whites, she says.
Clarification: After the story ran, WW (formerly Weight Watchers) contacted us to clarify that it does not encourage members to eat any food “with abandon” as our story originally stated. Instead, they say, zero-point foods are foods that don’t have to be tracked or measured on their diet plan.