The Difference Between Brown And White Eggs Can Easily Be Explained By Science

If you've found yourself lingering over egg cartons at the grocery store, wondering about the difference between brown and white eggs, you are not alone. Despite the conventional wisdom about brown eggs being healthier or somehow more "natural" than white ones, the truth is simple. The difference between brown and white eggs comes down to one thing — the breed of chicken that lays the egg.

Brown eggs are laid by chicken breeds such as Rhode Island Red, Speckled Sussex, Black Australorp, Buff Orpington, and Cuckoo Maran, to name a few. These chickens lay eggs in varying shades of brown, ranging from a light brown (Speckled Sussex) to a dark chocolate brown (Cuckoo Maran). White eggs are laid by a variety of Leghorn species (including White Leghorn, Silver Leghorn, and the colorful Blue Breasted Brown Leghorn), as well as Ancona, Silver Lakenvelder, and California White.

Strangely, according to The Guardian, although brown eggs are now considered superior to white ones by many people, a century ago, that wasn't quite the case. In England, people were used to white eggs, which were much more abundant than brown eggs since they were laid by highly productive White Leghorn chickens. The relative scarcity and novelty of brown eggs was what raised their popularity in the mid-20th century.

Nutritionally, brown and white eggs are the same, with the shell color not having any effect on the nutritional value or taste of what's inside the shell. The truth is, brown eggs (or white eggs) can vary in nutrition and taste depending on the food the chicken consumed, its environment, and the style in which it was raised, regardless of shell color. In general, free-range chickens who are free to roam around backyards tend to produce healthier and more natural eggs than chickens raised in cages or coops.

One reason for this difference is that free-range chickens are more likely to have access to a larger selection of vitamins and minerals. Another factor is sunshine, with chickens exposed to sunlight laying eggs that have 3 to 4 times the amount of vitamin D than caged chickens. The quality of the food consumed by the chickens also affects the nutritional value of the eggs they produce. For example, chickens that eat foods rich in omega-3 fatty acids lay eggs that contain a higher amount of omega-3 fatty acids. Regardless of whether such healthy supplements are present or not, eggs (or at least egg yolks) should still be consumed in moderation because of their high cholesterol content –one of the things that scientists know about cholesterol that you didn't (until now). 

Brown eggs acquire their color after ovulation, when the egg is released from the ovary into a tube called the oviduct, which is known as the fallopian tube in humans. At this stage of egg development in chickens, a shell forms over the egg and pigments are deposited in the shell. Brown and pink eggshell colors derive from a pigment called protoporphyrin IX, with the amount of this pigment determining the intensity of the brown color. The more protoporphyrin IX that gets deposited in the eggshell, the browner the egg. On the other hand, the less protoporphyrin IX, the pinker the egg. That's why different brown egg-laying chicken breeds lay different shades of brown eggs and why there is a range of colors even among chickens of the same breed.

Another eggshell color that is becoming increasingly prized is blue, which is caused by pigments called biliverdin IX and zinc biliverdin chelate. The amount of these pigments deposited in the shell determine the shade of blue, with more pigment resulting in a bluer egg. If no pigment is deposited during shell formation, the eggs will remain white.

According to a study in the journal Animal, eggshell color is passed down between generations and is controlled by multiple genes, with each gene contributing some effect. The way in which eggshell color is inherited in chickens is similar to how some human physical characteristics are passed down from parents to their children. Scientists have identified several genes that control the production of protoporphyrin IX on chromosome 20, as well as genes that control the production of other pigments. With that information, some day soon, farmers may be able to breed chickens that lay eggs of a specific color and shade.