Over 75 billion eggs are produced in the U.S. each year. That’s a lot of omelets. Most people know that eggs contain protein, but what else? Here are some egg nutrition facts, according to the USDA.

A single large egg laid by a hen contains 72 calories, as well as:

  • 5 grams of fat (1.5 grams saturated)
  • 6 grams of protein
  • 0.4 grams of carbohydrate

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More than 60 percent of calories in an egg come from dietary fat. About 35 percent come from protein. But when it comes to eggs, here’s the question many people debate: should I eat the yolk?

To eat the yolk or not?

hard-boiled eggSome people toss the yolk, but there's a lot of nutrition in that yellow chunk. (Photo: Piyathep/Shutterstock)

People wary of cholesterol and fat often chuck the yolks, but what many egg-white-only eaters don’t realize is that about half the protein in an egg is found in the yolk.

There are other benefits of eating the yolk as well.

Choline, though not a highly-touted nutrient in diet articles, plays an essential role in fetal brain development. Pregnant women need to eat the yolks to help prevent birth defects. Two whole eggs contain 250 milligrams of choline, about half the recommended daily value.

Yolks also contain two other nutrients that pregnant women need, including B vitamins, crucial for fetal nervous system and spinal cord development. The other nutrient is iron. Though an egg has only 5 percent daily value of iron, the iron found in eggs is a healthy mix of both sources of iron — heme and non-heme.

Eating two eggs, then, supplies a pregnant or breast-feeding woman with 10 percent daily value of iron, lowering the chance of developing anemia, something to which pregnant and breast-feeding women are more susceptible.

What if I’m not pregnant or breast feeding?

In most cases, you should still eat the whole egg. In addition to the B vitamins, almost the entire amount of the following vitamins and minerals are found in the yolk:

  • calcium
  • iron
  • zinc
  • selenium (nearly 25 percent of daily value)
  • phosphorous (10 percent of daily value)
  • Vitamins A, D, E and K (the fat soluble vitamins)

The yolks also contain heart-healthy omega-3 essential fatty acids.

And yet another reason to eat the whole egg is that yolks contain the full spectrum of essential amino acids. Eating only the whites will require food combining to make sure you get the complementary essential amino acids.

But what about cholesterol? Don’t the yolks contain a lot of it?

Yes, an egg yolk does have a lot of cholesterol. One whole egg contains approximately 200 milligrams of cholesterol, or roughly 70 percent of suggested daily values.

Don’t panic if you just gulped down a three-egg omelet. Your body naturally produces cholesterol for a variety of purposes, including making sex hormones, Vitamin D and bile acids to help digest fat.

If you eat foods containing cholesterol, your body doesn’t have to work as hard to produce it.

IN the past, dietary guidelines suggested that people limit cholesterol intake to 300 milligrams per day. Recently, however, new dietary guidelines have backed away from suggested restrictions on dietary cholesterol. The Dietary Guidelines Advisory Committee suggested that dietary cholesterol has little or no effect on blood cholesterol in most people.

Yolks also contain the antioxidant lutein, which is thought to promote eye health.

Are eggs the best source of protein?

sources of protein including eggs, nuts and cheeseMeat, nuts, cheeses and eggs are all sources of protein. (Photo: Milleflore Images/Shutterstock)

Eggs are considered by many the gold-standard of protein, especially for an all-natural source of food. For the average person, one egg has more than 10 percent of the daily value for protein.

More than 90 percent of a whole egg’s protein is absorbable by the body, which scores eggs way up high on the protein bio-availability scale.

Many bodybuilders place whey protein on a higher muscle-building pedestal than eggs, but whey protein isn’t a whole food like an egg.

Eggs cost roughly 25 cents each, making them one of the least expensive sources of complete protein, plus they’re easy to cook. Being a naturally nutritiously dense food, it’s no wonder eggs have been eaten for thousands of years.

Judd Handler is a nutrition and lifestyle coach in Encinitas, Calif.

This story was originally written in May 2011 and has been updated with the latest information.