Are eggs good or bad for you? The truth may be somewhere in between

CNN  — 

Forget which comes first, the chicken or the egg. The more important question is: Are eggs good or bad for your health?

Unfortunately, science can’t seem to settle on a definitive answer to that either.

Just last year, a large Harvard analysis of 215,000 people found that eating one egg per day was not associated with an increased risk of cardiovascular disease.

Now, a new study of over 500,000 people has found eating even a portion of a whole egg – with its cholesterol-laden yellow yoke – increases the risk of dying from all causes, including cardiovascular disease and cancer.

In fact, the overall risk of death went up by 7% for each additional half a whole egg eaten per day, according to the study published Tuesday in PLOS Medicine.

Experts were skeptical.

“Despite many years of research this question about eggs and health has not been answered, with multiple observational studies over the last few decades showing conflicting results – some suggesting moderate egg intake is good, while others suggesting it may be bad,” said Riyaz Patel, a consultant cardiologist at University College London.

“This study, although well conducted, unfortunately only adds more noise to the discussion,” Patel said in a statement.

The study results are problematic because they only asked people once about their egg consumption, then followed them for many years without checking to see if their diet had changed, said Dr. Walter Willett, a professor of epidemiology and nutrition at Harvard T.H. Chan School of Public Health.

“They’re only getting a snapshot in time,” said Willett, who is also a professor of medicine at Harvard Medical School.

“The conclusions of this study are overblown,” said Ada Garcia, a senior lecturer in public health nutrition at the University of Glasgow, Scotland, in a statement. “Blaming eggs alone for an increased risk of cardiovascular disease is a simplistic and reductionist approach to the concept of diet and disease prevention.”

What do eggs replace?

The poultry industry has long touted the “incredible, edible egg.” For a mere 75 calories, they say, an egg delivers 7 grams of high-quality protein, 5 grams of fat and 1.6 grams of saturated fat, along with iron, vitamins, minerals and disease-fighting nutrients like lutein and zeaxanthin.

One large egg can have about 185 milligrams of cholesterol.

Eggs are affordable, making them a cheap nutritional powerhouse for families with limited food budgets. Many people on popular low-carb diets such as keto also rely heavily on eggs in their meal plans.

The problem, of course, is the level of cholesterol in the yellow yolk of eggs: One large egg yolk can deliver about 185 milligrams of cholesterol.

Cholesterol is not a bogeyman. Made by the liver, cholesterol is in every cell in the body and is used to make hormones, vitamin D, digestive compounds and more. Sometimes a person’s body can make too much cholesterol, leading to a buildup of waxy plaque in blood vessels and later cardiovascular disease.

There is a role played by cholesterol in our diet, but it’s more complicated than we used to think, said Willett, who has spent over 40 years studying the effects of diet on the occurrence of major diseases.

Nutritional guidelines used to recommend an upper limit of 300 milligrams of cholesterol a day. Today guidelines suggest eating as little as possible by keeping saturated fats to less than 10% of daily calories.

The key, Willett said, is to look at the overall nutritional pros and cons of the food, as well as what the food is replacing in the diet.