Many egg lovers believe a glossy, sunset-colored yolk is more nutritious than a pale-yellow one. The color has become shorthand for high-quality and highly nutritious eggs that come with a much higher price tag. But color is actually one of the easiest things about an egg to manipulate with just a few tweaks.
With the right feed, egg producers can fine-tune yolk color on a spectrum from pale yellow to orange and red. The shade of the yolk is determined by carotenoids—plant pigments that are found in many foods, even bugs. And there is some evidence that certain carotenoids influence eye health in humans. Whether you should shell out for darker yolks, however, seems to come down to personal preference.
A hen’s digestive system pulls carotenoid pigment out of whatever the bird eats, and that pigment eventually gets deposited in the egg yolks. “That is what gives us the deeper color,” says Darrin Karcher, an animal sciences professor at Purdue University. The most common of these carotenoids are xanthophylls, found in dark leafy greens, peppers, corn and even algae. Eggs from pasture-raised hens can lean more orange because the birds have access to bugs and greens loaded with xanthophylls that a typical wheat-and-barley feed lacks. The shade can shift with the seasons because hens might forage more during the warmer months.
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But a darker yolk doesn’t necessarily mean a hen spent its life pecking around outside. Producers can “fake it” by adding certain foods rich in xanthophylls to the typical feed, says Stephan van Vliet, a nutrition scientist at Utah State University. Marigold petals or paprika can yield orange yolks—Vital Farms and other egg producers add these supplements to their feeds to deepen the yolks of their pasture-raised hens. On the other end of the spectrum, the addition of cottonseed meal can turn yolks an unappetizing olive green.
Egg producers will make changes to match the sensory expectations of consumers. Producers also want to keep yolk color consistent no matter where their eggs are sold, van Vliet says, and they rate them on a 16-shade yolk scale from palest to darkest orange, which is called the YolkFan. Research into consumer preferences by DSM-Firmenich, the company behind the scale, has shown that most people globally seem to prefer yolks with a darker orange color.
But whether it comes from paprika additives or foraged greens, the pigment in the eggs you eat may still benefit your health. Xanthophylls such as lutein and zeaxanthin reach the retina and accumulate as macular pigment, possibly slowing age-related macular degeneration, says Elizabeth Johnson, a nutritional biochemist at Tufts University.
In a study comparing similar doses of lutein from supplements, spinach and lutein-enriched eggs, Johnson and her colleagues found that the egg-sourced lutein was better absorbed by the body. This may be because the naturally occurring fat in the yolk helps eggs deliver the compounds especially well—the same reason a spinach salad drizzled in a fat, such as olive oil, is also a good source of lutein.
Even though eggs raise blood levels of lutein, their ability to improve vision or reliably increase the density of macular pigment has been inconsistent among other studies. Macular pigment, which filters blue light and acts as an antioxidant in the retina, increased meaningfully in older adults who were fed four eggs a day for a little more than a month. But some studies haven’t found that consuming eggs changes macular pigment density, and unlike vitamins or minerals, lutein isn’t considered an essential nutrient.
Any health claims that companies make about darker yolks should be treated with caution—such claims require demonstrating a clear health benefit for humans, Karcher says, which is a bar that has not yet been cleared. Van Vliet recommends choosing pasture-raised eggs because they are likely to have come from the happiest and healthiest hens—the ones seeing sunshine, having space to roam and eating a more diverse diet.
“If you know where your eggs come from, what they were fed,” van Vliet says, “that’s probably more important than just going by color.”