What an egg yolk's color can tell you about its nutrition value

Egg yolks vary wildly in color ― from soft yellow to dark orange, even red ― and our color preference often varies depending on where we’re from. But what does the color tell us about the quality and nutrition of our eggs?

Research says it’s complicated.

Historically, a richer-colored yolk meant a healthier, more nutritious egg. Chickens that graze naturally on grass, bugs and seeds are well-nourished and produce bright orange yolks with a high percentage of nutrients and healthy fats. Factory-farmed chickens, which live in tightly packed cages and primarily feed on grain, tend to have lighter yellow yolks whose nutritional content (literally) pales in comparison to their darker orange counterparts.

We’ve known for quite some time that the color of a yolk is determined by a hen’s diet, due to a group of nutrients called carotenoids, which also give butternut squash and carrots their deep yellow hues. The higher percentage of carotenoids in a hen’s diet, the richer the color of her yolk ― meaning farmers can easily control the color based on what they feed and how they raise their birds.

“We’ve found that the more we move [the birds] and the more access they have to pasture, the brighter the yolks,” said Joel Slezak, a farmer in Free Union, Virginia, who raises 700 laying hens through a process called rotational grazing. He and partner Erica Hellen move their birds to new sections of pasture three times a week, which gives chickens constant access to fresh, rich ground to forage.

“Our customers tell us all the time that if we’re not moving them around enough or there’s not enough nutrition in the pasture, it makes a big difference in the yolk,” he said. 

Dan Barber, chef and farmer at Blue Hill at Stone Barns, revealed in Season 1 of Netflix’s “Chef’s Table” that he feeds his chickens carotenoid-rich red peppers to achieve a bright, nearly blood-red yolk. But he does it less for the color than to prove a point: He’s an advocate for pasture-raised eggs and animals, and he wants to get people to pay attention “to not only what we’re eating, but what we’re eating is eating.”

RELATED: What you didn't know about eggs 

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Eggs are a tremendous ingredient to add to just about any meal. Since they can be prepared in so many ways, read on for more information on the versatile treat.

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Water Can Determine If An Egg Is Still Good.

If you place an egg in a tall glass of water and it sinks, then it is safe to eat because it means that the yolk is still heavy. Egg yolks shrink as they age and this creates air bubbles. If the egg floats, then it is time to throw it out.

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Egg World Records

Howard Helmer, a former American Egg Board representative holds three Guinness World Records for omelet making. Helmer has won for making 427 omelets in 30 minutes and has made the fastest single omelet taking 42 seconds (from whole egg to omelet). He has also completed 30 omelet flips in 34 seconds.

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Eggs Can Stand.

It is said that during the vernal equinox around March 21when the sun crosses the equator, making day and night equal everywhere, it is possible to stand an egg.

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Expiration Dates Aren't Exactly Right.

The expiration or sell by date on an egg carton doesn’t necessarily determine when an egg will go bad. The best by or use by date will better assess the quality of the eggs.

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Spinning Can Determine An Egg's State.

You can spin an egg to tell if it is raw or hard-boiled. Since the hard-boiled egg is filled with solids rather than liquids it will spin easily. A raw egg will wobble because the liquids are still present.

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Eggs Are A Good Hangover Cure.

This is due to their high content of cysteine, which helps to break down the cause of the hangover, acetaldehyde. Eggs also help to get rid of the toxins that alcohol leaves behind.

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Eggs Come From Other Birds.

Chickens aren’t the only birds who lay eggs. Eggs can come from emu, goose, ostrich, duck or quail.

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Eggs Aren't Only White.

Chicken eggs come in more colors than white and brown. Different breeds of chickens produce different colors. Some eggs can even appear blue, blue-green, reddish brown or speckled.

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Hens Lay A Lot Of Eggs.

An average hen can lay 250 to 279 eggs per year.

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Good Source Of Vitamin D

Vitamin D is generally associated with the sun, but you can get 10 percent of your daily intake by eating an egg.

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Synthetic Eggs Are On The Rise.

A San Francisco start-up is trying to make egg-less mayonnnaise and other egg-less products.

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Eggs Have A Lot Of Pores.

Eggs have 7 to 17,000 tiny pores on their shells. They also can absorb odors in the fridge, so make sure to keep them in the carton.

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Yolk Color Is Determined By Diet.

The plant pigments in a hen's feed affect the color in the yolk in a certain way. Natural yellow or orange substances like marigold petals can be used to enhance the color of the yolk.

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Most Eggs Come From...

China! In China, approximately 160 billion eggs are produced a year, while the US produces about 65 billion eggs a year.

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Eggs Contain Almost All Essential Vitamins.

Eggs have all the essential vitamins you need except for Vitamin C, and they also contain all the essential proteins and minerals that your body needs.

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A yolk can tune us into the health ― and even the living conditions ― of the chicken it came from.

A darker orange yolk tells us one of two things: that a chicken is eating a diet on open pasture, where they feed on carotenoid-rich grasses and flowers, or that they’re getting additives in their feed.

“We’ve learned that dark leafy greens and any orange/red fruits and veggies help give the yolk a very dark orange color,” said Amanda Nolan, co-owner and farmer of Dusty Hound Farms in Tetonia, Idaho. She cares for 50 laying hens on pasture that feed on bugs, grass and seeds in addition to ground-up fruit and vegetable scraps for added protein and nutrition.

“When we first started raising our chickens, their diet was mostly store-bought food and grain and occasional scraps from our house, but we weren’t seeing the rich dark yellow yolks that we wanted,” she said, adding that it took about a week to see yolks transform from pale yellow to rich orange after moving the chickens off of store-bought feed.

The egg on the left is from a hen that was fed only commercial feed. The egg on the right is from a hen that's been to pasture and fed Amanda Nolan’s fruit-and-vegetable mash for seven days.

Carotenoid-rich fruits and vegetables add nutrition to the yolk as well. Carotenoids have strong antioxidant properties and have been shown to prevent age-related blindness. And the color of the yolk shows us that these nutrients are making it into the egg.

“The egg is the dietary reference for a chicken, meaning that the egg is there to support life for a chick,” said Casey Owens Hanning, a professor in the poultry science department at the University of Arkansas. “It’s required to have everything it needs for that chick to survive and grow.”

RELATED: Best protein choices 

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Learn which proteins are best (and worst) for you and the world around you.

1. Lentils: Eat These Often

The most climate-friendly protein. We love lentils because they deliver fiber and nutrients, such as iron and folate.

2. Tomatoes: Eat These Often

Eating more fruits and vegetables can help ward off disease. They’re low in fat and calories and give you fiber and important micronutrients. But, EatingWell’s Nutrition Editors note, they don’t provide much protein (1 gram per tomato), so also make sure to include higher protein sources in your diet.

3. Milk: Drink This Often

Choose organic and/or milk from grass-fed cows. EatingWell editors recommend choosing nonfat or low-fat (1%) milk. Buying local milk will have a lower carbon footprint, too. Look for milk that is rBGH-free (growth hormone).

4. Beans: Eat These Often

Beans deliver protein, fiber and nutrients. Opt for dry beans, when you can, for the lowest carbon footprint.

5. Tofu: Eat These Often

Excellent source of plant protein. Keep in mind that if the label doesn't say USDA Certified Organic or non-GMO, there is a good chance it was made from genetically-modified soybeans.

6. Broccoli: Eat This Often

Broccoli gives you only 2 grams of protein per cup, so while it is a low-carbon food (and great for your health), the EatingWell Nutrition Editors note that you’ll need to include higher-protein sources in your diet.

7. Yogurt: Eat This Often

Choose organic and low-fat or nonfat yogurt when possible.

8. Nuts: Eat These Often

High in protein and healthy monounsaturated fats.

9. Peanut Butter: Eat This Often

EatingWell’s Nutrition Editors recommend looking for natural peanut butter to avoid extra sugar and partially hydrogenated oils.

10. Rice: Eat This Often

The EatingWell’s Nutrition Editors recommend choosing brown rice since it is less processed than white, retaining the fiber and other nutrients. Whole grains, such as quinoa or millet are also good choices.

11. Potatoes: Eat These Often

Buy organic when possible, since conventionally grown potatoes tend to be high in pesticide residues (they’re on the EWG’s “Dirty Dozen” list of produce most contaminated with pesticides.)

12. Eggs: Eat These Occasionally

For the lowest environmental impact, pick organic and/or pasture-raised. Look for certified humane.

13. Tuna: Eat These Occasionally

Rich in Omega-3 fatty acids. EatingWell’s Nutrition Editors choose light tuna to reduce mercury exposure.

14. Chicken: Eat This Occasionally

Best meat pick. EatingWell’s Nutrition Editors recommend that you cook it skinless to minimize saturated fat intake. Opt for organic, pasture-raised or antibiotic free for the lowest environmental impact.

15. Turkey: Eat These Occasionally

Poultry has the lowest carbon footprint of any meat, and turkey is a good choice. Opt for organic or antibiotic-free, but avoid less healthy processed forms (cold cuts, sausage, etc.).

16. Salmon: Eat These Occasionally

Choose wild salmon over farmed, when possible for the lowest carbon footprint. EatingWell’s nutrition editors note that salmon adds healthy omega-3s to your diet, so eat it and other fatty fish a few times a week.

17. Pork: Eat This Less

Choose pasture-raised, certified humane, when possible. For your health and the environment, skip processed pork, like bacon.

18. Cheese: Eat This Less

Stick to a single serving (1.5 ounces for hard cheese)—plus using a sharply flavored cheese can help you get the maximum impact for less. The EWG also recommends choosing organic and low-fat cheese, when possible. EWG lists cheese as the 3rd worst protein choice in part because they looked at 4 ounces of cheese—that’s almost three 1.5-ounce servings!

19. Beef: Eat This Less

Look for grass-fed and organic. Although pricier than conventional, it’s a healthier choice for you and the environment. Grass-fed beef is richer in heart-healthy omega-3 fats. Plus, organic, grass-fed cattle are raised in a way that minimizes the carbon emissions from manure. The EWG also recommends avoiding processed beef products, such as sausage.

20. Lamb: Eat This Less

The EWG ranked lamb as the worst choice based on carbon footprint and recommends choosing grass-fed, when possible. Since it’s not widely eaten in the United States, it plays a smaller role in carbon impact than beef, however.

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The healthier the chicken, the healthier the egg.

Caged chickens that don’t have access to the outdoors are given additives to alter the color of their yolks. Some of these additives (like algae, marigold flowers and orange peels) add some nutritional value, but the benefits don’t compare to a pasture-raised diet, which also gives chickens nutrients from the bugs, worms and seeds they eat in between grazing on grass ― specifically heart-healthy omega-3 fatty acids.

“If you enhance a hen’s diet with fat-soluble vitamins, they are readily reflected in the vitamin concentrations in the egg yolk, e.g. vitamin D, vitamin A and Vitamin E,” said Paul Patterson, professor of poultry science at Penn State University. “Similarly, the hen yolk reflects the fatty acid profile of her diet. If a hen gets more omega-3 fatty acids [in her diet], the yolk reflects that.”  

One study found that pastured eggs have two times the vitamin E and omega-3 fatty acids of factory-farmed eggs and 38 percent more vitamin A.

So can we determine the nutrition content or quality of an egg just by looking at it? 

Not exactly, but it certainly gives us a clue.

Ninety-seven percent of the eggs in the U.S. come from factory farms, so it’s safe to assume that cheap eggs with rich-colored yolks have been synthetically dyed.

This means we need to look for other cues of quality when buying eggs.

“The structure of a pastured yolk is very firm,” Slezak said. “If you crack it into your hand and let the white separate between your fingers, you can tell how much stronger it is. The whites won’t be as runny and the yolk won’t fall apart as easily.”

Labels can be misleading, too. “Organic” and “cage-free” mean very little these days. Even “free-range” means chickens are given only a small amount of fenced-in outdoor space, and it is often just cement. You can look for Certified Humane “Pasture-Raised” on labels, which guarantees at least some outdoor space.

But the highest-quality eggs probably come from your local farmers.

“We’re averaging 45 square feet per bird,” Slezak said of his hundreds of laying hens, which is a stark difference from the 2 square feet per birdrequired for even the most regulated “pasture-raised” eggs.

One final thing to keep in mind: Yolk color can vary throughout the year ― eggs, like everything, are a seasonal product, and even the healthiest birds lay less eggs and produce lighter-colored yolks in the winter. 

  • This article originally appeared on HuffPost.
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