Such products, however, have not yet appeared on the U.S. market. The color of the yolk is a reflection of its pigment content. In addition, the type of pigment in the egg and its concentration are directly influenced by the dietary concentration of any particular pigment. Consumer preferences vary greatly on yolk color, even in the same country. Yolk colors from 6 to 15 can be achieved by using only natural pigmenters obtained from natural raw materials.
Natural sources can be from plants such as marigold, chili, or corn.
The high protein blue-green algae known as Spirulina has also been shown to be a very efficient pigment source for poultry skin and egg yolk. Recent research has shown that eggs may be beneficial in preventing macular degeneration, a major cause of blindness in the elderly. A recent study indicated that higher intake of carotenoids reduced the risk of age-related macular degeneration. The most effective carotenoids were lutein and zeaxanthin, which are commonly found in dark-green leafy vegetables, such as spinach and collard greens. Most of the carotenoids in egg yolk are hydroxy compounds called xanthophylls.