By ANAHAD O’CONNOR | NYTimes.com

Question:

What is the current recommendation on eating eggs and heart health?

Answer:

Eggs were once considered off limits for many adults.

In the 1970s, groups like the American Heart Association discouraged people from eating eggs because it was thought that their cholesterol-rich yolks would increase the risk of heart disease. Now egg-white omelets are the norm for many people, but the advice on egg yolks has changed.

Clinical studies show that dietary cholesterol from eggs, shrimp and other animal foods has only a modest effect on blood cholesterol. In fact, public health authorities place more emphasis nowadays on the influence that dietary fat has on cholesterol levels.

The American Heart Association no longer condemns eggs in its guidelines. But it does recommend that people limit themselves to 300 milligrams of cholesterol daily (a single egg has about 200 milligrams of cholesterol, as well as a mix of saturated and unsaturated fats, including the monounsaturated kind found in olive oil). The federal government, in its Dietary Guidelines for Americans, notes that eating an egg yolk per day “does not result in increased blood cholesterol levels, nor does it increase the risk of cardiovascular disease in healthy people.”

That is in line with what studies have shown. In one large study published in JAMA in 1999, researchers found that consuming five to six eggs weekly did not raise the risk of heart disease or stroke in healthy adults. (There was not enough data to assess the impact of eating more eggs weekly.) Another large study published last year in BMJ also found that for most people, an egg a day was not bad for the heart.

Dr. Frank Hu, a professor of nutrition and epidemiology at the Harvard School of Public Health and an author of both studies, said that large amounts of dietary cholesterol might lead to “small increases” in blood cholesterol. “However, beneficial nutrients such as protein, vitamin B12, riboflavin, folate and vitamin D that are contained in egg yolks may counter the effects of cholesterol.”

Dr. Hu said that eggs are a particularly good replacement for less healthful fare, like processed meats and refined carbohydrates. In fact, studies suggest that for most people, starting your day with a breakfast of scrambled eggs will have a better impact on your overall cholesterol profile than a bagel or a bowl of sugary cereal.

Andrew’s Recommendation:

On any given day, we have between 1,100 and 1,700 milligrams of cholesterol in our body. 25% of that comes from our diet, and 75% is produced inside of our bodies by the liver. Much of the cholesterol that’s found in food can’t be absorbed by our bodies, and most of the cholesterol in our gut was first synthesized in body cells and ended up in the gut via the liver and gall bladder. The body tightly regulates the amount of cholesterol in the blood by controlling internal production; when cholesterol intake in the diet goes down, the body makes more. When cholesterol intake in the diet goes up, the body makes less.

This explains why well-designed cholesterol feeding studies (where they feed volunteers 2-4 eggs a day and measure their cholesterol) show that dietary cholesterol has very little impact on blood cholesterol levels in about 75% of the population. The remaining 25% of the population are referred to as “hyper-responders”. In this group, dietary cholesterol does modestly increase both LDL (“bad cholesterol” and HDL (“good cholesterol”), but it does not affect the ratio of LDL to HDL or increase the risk of heart disease.

In other words, eating cholesterol isn’t going to give you a heart attack. You can ditch the egg-white omelettes and start eating yolks again. That’s a good thing, since all of the 13 essential nutrients eggs contain are found in the yolk. Egg yolks are an especially good source of choline, a B-vitamin that plays important roles in everything from neurotransmitter production to detoxification to maintenance of healthy cells. Studies show that up to 90% of Americans don’t get enough choline, which can lead to fatigue, insomnia, poor kidney function, memory problems and nerve-muscle imbalances.