I recently joined President Obama on his trip through Africa, and I brought a mystery home with me. I wonder if you can help me solve it.
I was supposed to take my anti-malaria pills in the morning, with heavy or fatty food. That meant a lot of eggs for breakfast, all across Africa. In Senegal and South Africa, everything seemed normal. Then we arrived at the final stop of the trip, in Tanzania. When I picked up my vegetable omelet from the breakfast buffet at my hotel in Dar es Salaam, one glance suggested they'd accidentally made an egg white omelet. No big deal. I ate it without a second thought.
The next day, President Obama flew home, and I went to a remote island called Mafia for 36 hours of R&R. My first morning at the rustic lodge, I ordered scrambled eggs. They, too, were white. Could this chef have left out the yolks, too? Impossible.
The next day, determined to get to the bottom of this, I ordered my eggs sunny-side-up. (Not my favorite, but a sacrifice I was willing to make in the name of scientific research.) Sure enough, the runny yolks were ghostly pale. I asked the lodge manager, who'd lived in South Africa and England, why the yolks looked more like whites. "Oh, those eggs you get in the U.S. are only yellow because they're pumped full of hormones," he said.
But I know that's not true; I buy my eggs from my neighborhood farmers market, and the yolks are the color of a setting sun.
Could the color of the yolks have something to do with what the chickens are eating, or with the breed of chicken that lays them? I know that some chickens produce eggshells in shades of blue, pink, yellow or brown. Maybe the yolk color varies just as widely? But does that explain why the eggs were pale in both a Dar es Salaam chain hotel and a remote Mafia lodge?
Can you help me unscramble this puzzle?
White egg yolks may look bizarre, but poultry scientists I spoke with say there's nothing to worry about.
"I get that call every once in a while: 'My birds are freakishly pale!' " says Scott Beyer, a poultry specialist with the state of Kansas.
As you suspected, the reason Americans eggs tend to have bright yellow yolks has nothing to do with "hormones" but rather with what we feed our hens. Beyer says egg yolk color is almost entirely influenced by the birds' diet.
So if you're feeding birds yellow corn, "it gets in the egg," he explains. "But if you had a situation where you're feeding birds white corn, then the egg yolk could be white."
The yellow color in egg yolks, as well yellowish chicken skin and fat, comes from pigments found in plants called xanthophylls, primarily lutein, notes Han Jianlin, a geneticist at the International Livestock Research Institute.
In most parts of the world, he says, diners prefer their yolks with a sunnier disposition, so commercial feeds often contain lutein as an additive, though yellow maize, soybeans, carrots and alfafa powder will also do the trick. Sorghum – a grain with much less pigmentation than yellow maize — is used as chicken feed in Tanzania, which probably explains the pallid omelets you encountered.
On the other end of the rainbow, says Beyer, are the yolks in some parts of South America, where hens will peck at dark red annatto seeds. The result? Brilliant yolks ranging from dark orange to red orange to pink, Beyer says.
Many egg eaters assume that darker yolks are a sign of higher nutritional value, but both Beyer and Jianlin independently told me that's not the case at all. Although chicken feed does influence the nutritional value of birds and their eggs, the researchers say yolk color won't tell you anything.