NEW YORK (CBS NEWS) — A new, large study may serve up some confusing advice for egg lovers.
Research from Northwestern Medicine finds that adults who ate several eggs per week and high amounts of dietary cholesterol had a significantly higher risk of cardiovascular disease and death from any cause.
The findings suggest it may be time to re-evaluate the current U.S. dietary guidelines that no longer limit cholesterol or eggs, the researchers say.
“The take-home message is really about cholesterol, which happens to be high in eggs and specifically yolks,” one of the authors, Norrina Allen, Ph.D., an associate professor of preventive medicine at Northwestern University Feinberg School of Medicine, said in a statement. “As part of a healthy diet, people need to consume lower amounts of cholesterol. People who consume less cholesterol have a lower risk of heart disease.”
Prior to 2015, nutrition guidelines recommended eating less than 300 milligrams of dietary cholesterol per day. But that year, based on the available data at that time, the recommendations changed, eliminating the daily limit on cholesterol and focusing instead on the reduction of foods high in saturated fats.
The new research makes a strong case for bringing that limit back.
What the new study shows
Allen and her team pooled data on nearly 30,000 racially and ethnically diverse adults between 1985 and 2016. Participants were asked about their dietary habits over the last month or year in an extensive questionnaire. By the end of the follow-up period, the group had experienced 5,400 cardiovascular events and 6,132 deaths from any cause.
An analysis found that consuming 300 milligrams of dietary cholesterol per day was associated with a 17-percent higher risk of cardiovascular disease and an 18-percent higher risk of death.
Eggs were then looked at specifically because they are one of the richest sources of dietary cholesterol. One large egg contains about 186 milligrams of dietary cholesterol in the yolk.
The researchers found that eating three to four eggs per week was linked to a 6 percent higher risk of cardiovascular disease and an 8 percent higher risk of any cause of death. The findings were published today in JAMA.
Compared with previous studies, “this report is far more comprehensive, with enough data to make a strong statement that eggs and overall dietary cholesterol intake remain important in affecting the risk” of heart disease and death, Dr. Robert H. Eckel writes in an editorial published along with the study.
Why is there so much conflicting guidance on eggs?
With so much conflicting evidence, it can be hard for consumers to keep track of which foods are considered healthy choices.
“I can totally understand that people would be confused and frustrated,” Dr. Leslie Cho, a preventive cardiologist at Cleveland Clinic, told CBS News.
She notes that while the JAMA report is scientifically sound and well-done, like any study it has its limitations.
“It’s a very large study with a very large number of different types of patients. These are all good things,” she said. “But in general, any dietary study is fraught with difficulty because of the problem of patient recall. Do you remember what you ate last week? Because I don’t. It’s the same thing with patients.”
Most dietary studies are also observational, making their findings less reliable. That’s because unlike a randomized controlled trial that tests the safety and efficacy of a drug, it’s difficult to randomly control what people eat over a long period of time, especially with a large sample size.
However, though flawed, Cho says these studies are important for a better understanding of nutrition research.
“In science, the way it works is we don’t think of it as one study having the final word,” she said. “In science, we look at the preponderance of evidence to see where the field is going.”
Bottom line: Moderation is key
It’s important to note that no one, including the study authors, is saying you need to cut eggs completely out of your diet.
“We want to remind people there is cholesterol in eggs, specifically yolks, and this has a harmful effect,” said Allen, who mentioned that she still cooks scrambled eggs for her children. “Eat them in moderation.”
Cho says she never stopped recommending her patients limit their dietary cholesterol intake to 300 milligrams a day or told patients they could eat as many eggs as they want.
“In addition to dietary cholesterol, there’s a cancer risk involved in eating eggs and other animal products,” she said. “We’ve always said you can have egg whites but you should probably limit your amount of egg yolk consumption.”
She recommends sticking to a Mediterranean diet, which is rich in heart-healthy plant-based foods that are also low in cholesterol, including fruits and vegetables, whole grains, legumes and nuts.
“Time and time again, it’s been shown to improve survival,” Cho said. “This is the diet we should be adopting.”
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