Q. Is there any nutritional difference between brown and white eggs? What accounts for the difference in shell color?

A. There is no discernible difference in nutritional value, said Tro V. Bui, a visiting fellow in animal science at Cornell University. Brown eggs in general may have more omega-3 fatty acids, but the difference is tiny, he said. There is no difference in yolk color or taste.

Genes determine shell color, Dr. Bui said. White-feathered chickens with white earlobes lay white eggs; red or brown ones with red earlobes lay brown eggs; and the Ameraucana breed, also known as the Easter egg chicken, lays eggs with blue shells.

Shell quality does not differ by breed, though younger chickens lay eggs with harder shells. Brown-egg chickens tend to be larger and cost more to feed and raise, so white eggs are more cost-efficient.