October 01, 2016
brown and white eggs in an egg carton with a yellow background

The Sunny Side of Eggs

by Berkeley Wellness  |  

Eggs have a bad reputation because of their high cholesterol content: 185 milligrams in the yolk of a large egg. But, in fact, dietary cholesterol has relatively little effect on blood cholesterol in most people (saturated and trans fats are the bigger culprits)—and more recent research, including two new studies, has largely exonerated eggs and even suggested that they may provide some heart benefits.

Eggs and your heart

You may be surprised to know that dietary cholesterol, found in animal foods, raises blood cholesterol in only about one-third of people. And, as shown in some egg studies, dietary cholesterol causes the body to produce HDL (“good”) cholesterol along with LDL (“bad”) cholesterol in these “hyper-responders,” thus helping offset potential adverse effects. Moreover, the LDL particles 
that form are larger in size—and larger LDL particles are thought to be less dangerous than small ones.

Several years ago, research from the University of Connecticut found that eating three eggs a day for 30 days increased cholesterol in susceptible people, but their LDL particles were larger, and there was no change in the ratio between LDL and HDL, which suggests no major change in coronary risk. In a more recent study from the same university, published in Metabolism in late 2012, 40 middle-aged people with heart and diabetes risk factors ate either three eggs or cholesterol-free egg substitute daily, while also moderately restricting carbohydrates. After 12 weeks, total and LDL (“bad”) blood cholesterol did not change in either group. Moreover, though both groups showed a range of cholesterol improvements due to the carb restriction, the egg eaters had a greater boost in HDL (“good”) cholesterol as well as increases in sizes of both HDL and LDL particles, which was attributed, at least in part, to types of fat in eggs called phospholipids.

More significantly, eggs do not appear to contribute to heart disease in most people. A pivotal study from Harvard in 1999, of nearly 120,000 men and women, found no association between eggs—up to one a day—and heart disease, except in people with diabetes. Nor did it find a link between eggs and strokes. Studies since then have similarly vindicated eggs, including a Japanese study of more than 90,000 middle-aged people published in the British Journal of Nutrition in 2006, and a study in 2007 from the University of Medicine and Dentistry of New Jersey, which both found no link between frequent egg consumption and heart disease. Most recently, an analysis of eight observational studies found no relationship between eggs (up to one a day) and heart disease or stroke. Published this year in BMJ, it included nearly half a million people who were followed from 8 to 22 years, on average.

In light of these findings, recommendations about eggs have changed over the years, and cholesterol guidelines, in general, are being rethought.

The unsaturated fats and other nutrients, including B vitamins, in eggs may even be beneficial to heart health. It’s the foods that typically accompany eggs (bacon, sausage, cheese and biscuits) and how eggs are often prepared (fried in lots of butter) that can raise blood cholesterol and the risk of heart disease. A large egg has only 1.5 grams of saturated fat and about 70 calories. A Bacon, Egg & Cheese Biscuit from McDonald’s, on the other hand, has 12 grams of saturated fat (59 percent of the daily value for someone eating a 2000-calorie-a-day diet) and 420 calories, along with 1,130 milligrams of sodium.

Good for your eyes . . . and maybe your waist

Egg yolks are a rich source of lutein and zeaxanthin, relatives of beta carotene that may help keep eyes healthy and have been linked to a reduced risk of age-related macular degeneration. Not only are these carotenoids well-absorbed and better used by the body than those from spinach or supplements, but a study in the Journal of Nutrition in 2006 also found that women eating six eggs a week for 12 weeks had increased macular pigment, which is thought to protect the retina of the eye from the damaging effects of light.

There’s some evidence that eggs promote satiety, due in part to their protein. For example, in a study in Nutrition Research in 2010, men who ate an egg breakfast (three scrambled eggs and toast) felt fuller afterwards and consumed significantly fewer calories at lunch and over the next 24 hours than men who ate a bagel-based breakfast with the same number of calories. An earlier study reported similar findings in women eating two eggs for breakfast.

What’s in an egg?

  • One large egg contains 6 grams of high-quality protein (in both the yolk and the white). The yolk is also a source of zinc, B vitamins (including riboflavin and folate), vitamin A, iron and other nutrients. According to a USDA analysis a few years ago, eggs contain 14 percent less cholesterol than they used to—one large yolk now has about 185 milligrams compared to about 210 earlier, possibly because of changes in hen feeding practices.
  • In addition to lutein and zeaxanthin, egg yolks provide choline, an essential nutrient, which is especially important for fetal brain development. Researchers have also identified other compounds in eggs that may have anti-cancer, anti-hypertensive, immune-boosting and antioxidant properties.
  • “Designer” eggs, from chickens fed special diets, usually contain more lutein, vitamin E, and/or heart-healthy omega-3 
fats. But they rarely provide enough extra nutrients to be worth their higher cost. Eggs that claim to be rich in omega-3s, for example, contain only a small amount compared to fatty fish, such as salmon.
  • Brown eggs are not more nutritious than white. Different breeds simply lay eggs with different shell colors—even blue and green. Yolk color depends on what the chicken ate: wheat and barley produce a light yolk, corn a medium-yellow yolk, and marigold petals a deep yellow. Though not a sure indication, darker yellow yolks may have more omega-3s and carotenoids. Organic eggs, from chickens fed an organic diet, do not have more nutrients than conventionally produced eggs, though some people may prefer them as a way to support organic production.

Words to the wise:

Many of the egg studies have been funded by the egg industry and have lasted only a few months, so the long-term effects of eating a lot of eggs are still largely unknown. Still, eggs are good food. Most people can eat an egg a day (the equivalent of seven a week), or perhaps more, without ill effects—and with possible benefits. Just don’t mess them up by preparing them with fatty, salty ingredients or serving them with unhealthy side dishes.

Originally published March 2008. Updated May 2013.