I grew up eating eggs from white shells; I didn't know they could be any other color.

Our eggs came from the grocery store in Styrofoam packaging, and the eggs in the refrigerators at all my friends' houses were exactly the same. Growing up in suburbia in the 1970s and '80s meant no farmers markets, no trips to farms and no concept of food variety.

When I began buying my eggs at the farmers market, things changed. The eggs were brown and usually in paperboard cartons or Styrofoam cartons that were clearly being re-used.

I know I'm not the only one who had that experience with eggs, so it's no wonder that many people assume brown eggs are more nutritious. If we're working off the assumption that all white eggs at the grocery store come from big factory farms and that all brown eggs come from local farmers who raise free-range chickens ... sure. Brown is better.

But is that true?

What determines the color of an eggshell?

Eggshell color is determined by the breed and genetics of the hen, not by the conditions in which the chicken is raised. Generally speaking, you can tell whether eggs will be white by looking at a hen's earlobes, the colored skin on the side of the head. Hens with white earlobes generally lay white eggs. Hens with brown or reddish earlobes generally lay eggs that are brown, or sometimes light green, blue or a speckled creamy color, according to Michigan State University Extension.

No one breed of hen, however, is proven to lay a more nutritious egg than another, despite the color of the eggshell. Not all eggs are created equal because not all hens are raised the same way.

The hen's conditions can affect the egg's nutrition

Free-range chickens exploring a pasture Free-range chickens are allowed to explore the great outdoors ... if they can get there. (Photo: sevenke/Shutterstock)

A test done by Mother Earth News on eggs taken from 14 flocks around the country whose hens were allowed frequent access to fresh pasture found that true free-range eggs were nutritionally superior to eggs sold in grocery stores. When they compared the nutrition in the free-range eggs to the official U.S. Department of Agriculture nutrition data for commercial eggs, the eggs from those hens in the pasture contained:

  • 1/3 less cholesterol
  • 1/4 less saturated fat
  • 2/3 more vitamin A
  • 2 times more omega-3 fatty acids
  • 3 times more vitamin E
  • 7 times more beta carotene

"True" free-range means just that. Eggs from the grocery store that are marketed as free range do not necessarily come from hens that have spent their days roaming the barnyard, getting fresh air and eating a natural diet. When "free-range" is on an egg carton, it means that the chickens can move around their building and have access to the outdoors "during their production cycle."

But access doesn't guarantee time outside. There's no regulation that says getting to that door has to be easy, how big the outdoor area must be, or that a chicken ever has to get outside. A chicken in a crowded henhouse may never get to the door, and if it manages to go through it, may find there's no room for it in the small area outside.

That's why it's so hard to determine if free-range eggs at the store come from truly free-range chickens. At a farm or farmers market, you can ask about the conditions that the hens are raised in before you buy.

Another factor in the nutrition of an egg is the hen's diet. Although chickens are not vegetarians by nature — bugs and worms are part of their natural diets — Consumer Reports tested grocery store eggs and found that "hens fed vegetarian diets tended to have more of certain vitamins and omega-3s than those from hens fed a conventional diet."

So when you're choosing eggs and aiming for nutrition, don't judge an egg by its shell color. White eggs can be just as nutritious as brown eggs. Hens that are raised in conditions that are natural to them — with access to the outdoors, sunlight and exercise — and fed a good diet are what you're looking for. To find them, you'll need to ask some questions and, perhaps, pay a little more, because raising hens in pastures costs more than raising them at factory farming.

Robin Shreeves ( @rshreeves ) focuses on food from a family perspective from her home base in New Jersey.