According to the Egg Nutrition Center, about 280 million hens produce some 60 billion eggs each year in the United States. Since a good majority of those eggs end up in our stomachs, I thought it would be helpful to unravel some of the mystery surrounding the egg.

Q. I've heard eggs can raise my cholesterol. Is that true?

A. Not really. It turns out that normal intake of dietary cholesterol from foods doesn't elevate blood cholesterol (produced naturally in our bodies) to a point of concern — saturated fat does.

"The type of fat we eat, not cholesterol, is what is correlated with increased blood cholesterol levels," explains Anne VanBeber, associate professor and head of the department of nutritional sciences at Texas Christian University.

Dietary cholesterol has some effect on blood cholesterol, but it's not an issue unless you eat a lot of eggs, says Bonnie Liebman, director of nutrition at the Center for Science in the Public Interest. The American Heart Association recommends an intake of 300 milligrams or less of dietary cholesterol a day (one large egg contains 215 milligrams).

However, if you have total cholesterol over 240 milligrams per deciliter, a family history of heart disease, diabetes, high blood pressure, or you smoke, aim for no more than 200 milligrams of cholesterol per day, says Tanya Zuckerbrot, a Miami-based nutritionist.

Q. Are there other reasons eggs are considered unhealthy?

A. Yes. If you regularly eat eggs, you may also be cooking them with butter, sausage, bacon and cheese, all of which raise blood cholesterol.

Q. Do eggs have any health benefits?

A. Yes. One egg packs in 6 grams of protein (a little more than half in the white). "In fact, the FAO (Food and Agriculture Organization) of the United Nations classifies eggs as the highest protein source, above other protein of a food by analyzing its amino acid content, its digestibility and the amino acid requirements of the animal species that eat it," says VanBeber.

Additionally, eggs have a lot of beta-carotene. "Specifically, lutein and zeaxanthin are found in the yolk. These two carotenoids have been shown to decrease macular degeneration, which causes irreversible blindness," says VanBeber.

The Journal of the American College of Nutrition has cited the high choline (said to have a role in early brain development) content of the egg. Eggs also contain 15 percent of the daily requirement for riboflavin (an important B vitamin necessary for metabolism) and 17 percent for selenium (an important antioxidant mineral).

Q. Are there other reasons to eat eggs?

A. Eggs cook quickly and are ready within minutes. They're easy to eat (important for the young and elderly) and store. Plus, hard-boiled eggs are portable and make a great low-calorie snack. And they're an inexpensive source of protein.

Q. Can you explain egg grading?

A. According to VanBeber, egg grading is voluntary and is done for the benefit of the consumer. "The grade refers to the quality of the egg and what it will look like when cracked open. It has nothing to do with spoilage."

Q. Are there expiration dates on egg cartons?

A. All USDA-inspected egg cartons must carry the date the eggs were packed. That's not the same thing as an expiration date, although many brands voluntarily label their cartons with a date beyond which the eggs should not be sold. That date can be no more than 30 days from the packing date for USDA-inspected eggs.

Q. How should you store eggs?

A. "Eggs have porous shells, so it's best to keep them in the carton they come in or in a covered container in your refrigerator — don't use the egg slots in the refrigerator, or they'll become stale quicker," says VanBeber. Eggs can last four to five weeks after the expiration date.

Q. Do the white and yolk have different nutritional values?

A. While both have protein, the albumen (the egg white) has a little more than half the total protein in an egg (about 3.5 grams) and none of the fat.

Q. Can eggs make me sick?

A. It's possible, but highly unlikely — only one egg in 20,000 contains salmonella bacteria, according to most experts. Cook eggs until the yolk and whites are both firm (160 degrees) to eliminate the risk of any bacteria surviving. "Or buy already pasteurized eggs if you like your eggs runny — you can use them freely without worry of salmonella," says Andrea Dunn, of the Westlake Family Health Center at The Cleveland Clinic.

Q. What if you get a blood spot in an egg?

A. Blood spots sometimes (albeit rarely) are found in the egg's yolk. Less than 1 percent of all eggs have blood spots, which, contrary to popular belief, do not indicate a fertilized egg. They are caused by a rupture of the blood vessel on the yolk surface while the egg is being formed. It is a sign of freshness.

Q. What's the difference between brown and white eggs?

A. None. White-shelled eggs are produced by hens with white earlobes. Brown-shelled eggs are produced by hens with red earlobes. There is no difference in taste or nutrition between white and brown eggs, says Rebecca Odabashian, a nutritionist at Levindale Hebrew Geriatric Hospital in Baltimore.

Charles Stuart Platkin is a nutrition and public-health advocate. Write to info@thedietdetective.com.