Chances are, you've probably been ditching egg yolks (or avoiding eggs entirely) for years, thinking you were doing your heart a favor. But current research suggests that eggs may not be the demons they've been made out to be.

In fact, according to a study funded by the National Institutes of Health, eating one egg per day does not increase a healthy person's risk of heart disease or stroke. (If you're unsure whether this applies to you, consult your doctor.)

Since eggs are chock-full of nutrients, relatively low in calories, inexpensive and delicious in everything from breakfast to late-night snacks, that's good news all around. If only the seemingly endless variety of carton labels weren't so confusing....

How to Read an Egg Carton
It used to be that only two things mattered: size (from Peewee to Jumbo, though most recipes call for Large) and grade (which ranks the ratio and quality of white to yolk, with AA being the highest). While brown eggs cost more, "brown" only indicates the color of the laying hen's feathers! These days though, a visit the supermarket confirms that things have changed, with more egg varieties on display than would fit in a carton. Here's what it all means:

Animal Care Certified/United Egg Producers Certified
Egg producers who use this insignia treat their hens according to basic guidelines for housing, feeding and handling established by an industry group; 80 percent of the nation's eggs meet these standards.

Antibiotic-Free
Indicates that chickens laying these eggs received no drugs, but there is no official inspection program to verify these claims.

Cage-Free
Means exactly what it says, although the hens might be packed just as tightly into a shed as they would be in a cage.

Certified Humane
Overseen by the non-profit organization Humane Farm Animal Care, these egg producers meet specific, high standards for farm animal treatment: This means having enough space for the hens to move naturally, and thoroughly trained caretakers.

Certified Organic
Nutritionally identical to their non-organic brethren, these eggs come from hens who eat organic feed and have access to the outdoors.

Fertile
Eggs from hens that live with a rooster. Though they cost more to produce (and they spoil faster), there is no nutritional benefit. Nor is there any real difference in the egg itself, since refrigeration prevents embryos from developing.

Free-Farmed
A trademark of the American Humane Association, which certifies that the hens are raised humanely, in a cage-free environment.

Free-Range/Free-Roaming
A misleading label. These chickens were given access to the outdoors, but it might be as little as five minutes per day.

Grass-Fed
From hens fed grass rather than grain, which makes them more expensive to produce. Some suppliers claim that these eggs are higher in Omega-3 fatty acids (see below for more details).

Natural
More about marketing than meaning. According to the USDA, these eggs have "no artificial ingredient or added color and [are] only minimally processed," which applies to virtually every egg sold today.

Omega-3 Enriched
Hens are fed a special diet containing flaxseed, which is higher in Omega-3 fatty acids than other grains, yielding eggs higher in this heart- and vision-healthy substance. The total fat and cholesterol remains the same as the non-enriched variety.

Vegetarian-Fed
Exactly what it implies: The hens laying these eggs receive only vegetarian feed (no animal byproducts mixed in). Nutritionally, though, they're identical to other eggs.

One More Thing...
One other label, which appears on all USDA-graded egg cartons, is perhaps most confusing of all: that mysterious code printed on one end. It's not some arcane, complex secret-it simply shows the date and place where the eggs were packed. The three-digit code on the left notes the date, according to the 365 days of the year (so "035" equals the 35th day of the year, February 4). And the code on the right beginning with a "P" is the USDA-assigned number of the packing plant. Often you'll also see a more easily-recognized date. If it's preceded by the words "EXP," "Sell By," or "Not to be sold after," the date is at most 30 days after packing. On the other hand, if it says "Use by," "Use before," or "Best before," the date might be as much as 45 days out. Individual processors decide for themselves which to use.

Cooking with Eggs
Now that you know the ins and outs of egg-buying, here are some of our favorite ways to use them in every course, from breakfast to dessert.