Egg Nutrition

Eggs are considered a complete source of protein. The combination of amino acids in an egg is used as the standard for protein quality in other foods.   One egg has only 75 calories, 7 grams of protein, 5 grams of fat, and 1.6 grams of saturated fat, along with iron, vitamins, minerals, and carotenoids including lutein and zeaxanthin.   Egg whites contain most of the protein while egg yolks contain most of the fat as well as other beneficial compounds such as lecithin and biotin, both of which aid in the digestion of the egg.

Although eggs are high in cholesterol, research has not shown an increase in heart disease in people who consume eggs. Cholesterol in food does not seem to raise blood cholesterol as much as saturated fat and hydrogenated oils.  So today, eggs have returned to the forefront of recommended sources of protein as well as other nutrients.  

The color of eggs is an indicator of chicken variety or breed only.  Grading of eggs (AA, A, or B) is a voluntary program run by the USDA that rates the interior quality of the egg along with the appearance and condition of the shell.  Eggs are typically marketed as standard cage eggs, cage-free, free-range, organic, vegetarian, nutrient enhanced, pasteurized, not pasteurized, fertile and unfertile.  The size of eggs is regulated as follows.

Size or Weight Class

Minimum net weight per dozen


30 ounces

Extra Large

27 ounces


24 ounces


21 ounces


18 ounces


Nutrient enhanced eggs, sometimes called designer eggs, are from chickens whose feed is controlled to change the nutrition profile of the egg.  For example, to increase the amount of Omega-3s in eggs, chicken feed is enhanced with canola oil, bran, kelp, flaxseed, marine algae, fish oil, or Vitamin E.  In other cases, the feed is designed to reduce the saturated and total fat content of the egg yolk.   Marigold extract used to increase the lutein content of eggs is another example of nutrient enhanced eggs.

Eggs should be stored in the refrigerator and cooked thoroughly to kill any potential bacteria, including Salmonella.

Vegetarian, Pasteurized, Fertile & Non-Fertile Eggs

Vegetarian eggs are produced from chickens that are given strictly vegetarian feed.  By nature, chickens are omnivores and when allowed to roam, eat insects along with seeds and grasses.  Chickens raised to produce vegetarian eggs are given strictly controlled vegetarian feed without any animal byproducts.   Ovo-vegetarians are one group of customers who seek out vegetarian eggs.

Eggs are not required to be pasteurized; however, because eggs can carry harmful bacteria when eaten raw, pasteurized eggs are now more readily available.  Pasteurized eggs are especially used for commercial purposes where eggs are processed to remove the shells and the resulting liquid egg whites, yolks, or whole eggs are packed in large containers.    Pasteurized eggs are put through a pasteurization process where they are heated to 140 degrees Fahrenheit for three and a half minutes.    The pasteurization completely kills bacteria without cooking the egg.   Eating pasteurized eggs is recommended for young children, the elderly, and people with weakened immune systems so the risk of contracting a salmonella infection is reduced.

Hens are capable of producing an egg without the presence of a rooster.  Non-fertile or sterile eggs are from farms where only hens are kept.   Most commercially produced eggs have no potential for fertilization.  Fertile eggs are from farms that keep both hens and roosters.   Once the fertilized egg is stored inside the fridge, the embryo no longer undergoes any change or development.   According to the American Egg Board, there is no nutritional difference between the two and there are no risks to consuming fertile eggs.  However, ovo-vegetarians have a strong interest in this issue and prefer to consume non-fertile eggs.

Cage-Free, Free Range, Pasture Raised (or Free-Roaming), and Organic Eggs

The vast majority of conventional egg farms produce eggs from chickens housed in long lines of stacked cages with about eight birds to a cage.  Consumers have long been campaigning against this practice resulting in a variety of different production methods. 

Why This Matters:

Most customers in natural product stores are looking for sustainable and humane production methods.  Demand has grown for eggs and egg products to come from more humanly raised chickens.  As the industry adapts its production methods, it generates new terms and definitions often creating confusion in customers.  Staff should be prepared for the customers that will ask about the difference between cage-free and free-range and the meaning of other labels that are stamped on egg packages.

Cage-free hens are not confined to cages but are housed in large barn systems. The hens have bedding material such as pine shavings on the floor, and they are allowed perches and nest boxes to lay their eggs.   However, they may not have access to the outdoors and may live with thousands of other chickens at close quarters.  Their environment and eggs are not audited by a third party.   

While the USDA has defined the meaning of "free-range" for some poultry products, there are no standards for eggs labeled free-range. Typically, free-range egg-laying hens are uncaged inside barns or warehouses and have outdoor access.  They can engage in many natural behaviors such as nesting and foraging.  However, there are no requirements related to stocking density, the frequency or duration of outdoor access, or the quality of the land accessible to the bird and there is no third-party auditing.  Pasture-raised or free-roaming eggs, on the other hand, means that the hens have been allowed to freely roam in the outdoors where they can eat bugs and plants, flap their wings, take dust baths and behave in natural chicken manners.

Recent research indicates that “enriched cages” for egg-laying hens may be a better choice for hen welfare, with fewer fractures, lower mortality rates, lower stress levels, and less damage from pecking.  Free-range or pasture-raised hens can be distressed by poor weather, predators, or competitive, pecking behavior.   Enriched cages are large cage enclosures housed indoors that can accommodate flocks of 70 or 80 birds with access to food, water, perches, scratching posts, and nest boxes.  

Certified organic eggs come from hens that are generally cage-free.  The grains used for the hens’ diets must be produced on land that has been free from the use of toxic and persistent chemical pesticides and fertilizers for at least three years.  Genetically engineered crops are not permitted, and hens must be maintained without hormones, antibiotics, and other intrusive drugs.


Words to Remember


Chickens are raised in an open barn environment and are free to roam around the floor, perch on rods, and scratch in hay bedding, but they are not allowed to go outside the barn.



Means that the animal must be given some amount of time for outdoor grazing. Chickens labeled "free-range" must have access to the outdoors, although this need not be pasture and may be dirt or gravel areas. There are no regulations for other animals from whom meat products are labeled free-range, except for products labeled Organic. Some animal welfare certifying agencies establish specific standards for raising animals certified as free-range.