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If you enjoy eating eggs you may worry about harming your heart. Don't stress. If you're healthy, you can eat eggs guilt-free. But how many and how often?
Nutritionally, eggs have a lot to offer. With about 70 calories in one large egg, they're a great source of protein that helps stabilize blood sugar levels and provides structure to the body. Egg protein is also high quality, providing all the essential amino acids.
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Egg yolks also contain antioxidants that may reduce the risk of age-related macular degeneration and cataracts, and protect against heart disease, stroke and some cancers. One large egg is also an excellent source of selenium, an antioxidant mineral that fights cell damage caused by free radicals and supports thyroid and immune function and riboflavin, a B vitamin that helps turn carbohydrates into energy, and vitamin D, important for strong bones and teeth.
All good stuff. So is an egg a day OK?
The science is not entirely clear.
A 2016 study published in the American Journal of Clinical Nutrition found that eating one egg a day was not associated with an increase in heart risks. That's on top of a 2003 study published in the British Medical Journal, which tracked 115,000 adults for 14 years: researchers found eating one egg daily was not associated with an increased risk of coronary heart disease and stroke.
Eggs can also fill you up, and may even help you eat less.
In a study published in 2013 in the European Journal of Nutrition, 30 healthy men were randomly assigned to eat one of three breakfasts—eggs on toast, cornflakes with milk and toast or a croissant and orange juice—on three separate occasions, each separated by one week. Subjects felt more full and less hungry and had less desire to eat after the egg breakfast than the other breakfasts. They also ate less at lunch and dinner after having the egg breakfast as opposed to the other breakfasts.
In another study published in 2011 in the International Journal of Food Science Nutrition adults ate three lunches — an omelet, a skinless potato or a chicken sandwich (each had similar calories) — following a standard breakfast. Researchers found that the egg lunch was significantly more satisfying than the potato lunch. They concluded that eggs for lunch could increase satiety more than a carbohydrate meal and might even help reduce between-meal calorie intake.
Since the link between excess weight and heart disease is well established, thumbs up to eggs for appetite control.
But there are cautions. Eggs are a source of saturated fat and too much saturated fat has been shown to raise total cholesterol and LDL (bad) cholesterol levels, risk factors for cardiovascular disease.
While one large egg contains about 1.6 grams saturated fat, more than half the fat in an egg — 2.7 grams— comes from heart-healthy monounsaturated and polyunsaturated fatty acids (including omega 3's) combined.
One large egg contains about 180 milligrams of cholesterol. It's advised to cap dietary cholesterol at 300 milligrams daily. For those with heart disease, type 2 diabetes or high LDL (bad) cholesterol levels, the American Heart Association and National Cholesterol Education Program (NCEP) suggest limiting cholesterol intake to 200 milligrams daily.
In a study published in 2012 in Atherosclerosis, carotid plaque build-up in the arteries was measured and self-reported habits (including egg yolk intake and cigarette smoking) were assessed in 1,231 older adults. Researchers found that while plaque build up occurred steadily in participants after about age 40, those who ate the most egg yolks — three or more weekly — had plaque build up similar to (thought not quite as bad) as that seen in cigarette smokers.
Although hyped in the media, several experts questioned the findings and the quality of the study.
But another study published in The New England Journal of Medicine found that eating two hard-boiled eggs daily increased the formation of trimethylamine N-oxide (TMAO), a chemical linked to an increased risk of heart attack and stroke. Egg yolks contain lecithin, an essential fat that contributes to TMAO formation.
That's why it's prudent to stick to the American Heart Association recommendation of up to one egg per day or seven per week.
It can be hard to know how many eggs or egg product we consume each week.
Try to limit yourself to one whole egg (and add a few extra egg whites and fresh vegetables) when making scrambled eggs, omelets and frittatas. It's fine to have a few additional egg whites during the week.
Be aware of other foods typically made with eggs, including baked goods, French toast, Caesar and some other salad dressings, meatballs, and meat loaf. If you're at risk for or have high cholesterol, heart disease or type 2 diabetes, it's wise to cut back on other animal foods high in saturated fat and cholesterol.
Elisa Zied, R.D. is a New York nutritionist and author of "Younger Next Week."
This updated article was originally published in December, 2014