Yes, an Unfertilized Egg Does Have Protein: Understanding the Nutritional Facts

December 20, 2025 •

3 min read

According to extensive nutritional studies, there is no significant difference in protein content between unfertilized and fertilized eggs. A chicken’s reproductive process means that an unfertilized egg does have protein, as the hen’s body naturally produces a complete egg with all its components, regardless of fertilization.

Quick Summary

Unfertilized eggs, like those sold in grocery stores, are a high-quality, complete protein source, and their nutritional makeup is fundamentally the same as fertile eggs. Both the yolk and albumen contain essential proteins necessary for biological function.

Key Points

Yes, Protein is Present: An unfertilized egg contains a rich source of high-quality protein, with no significant difference in protein content compared to a fertilized egg.
Yolk and White Contain Protein: Both the egg white (albumen) and the yolk are packed with various proteins, though their specific protein compositions differ.
Complete Protein Source: Egg protein is considered a 'complete' protein because it provides all nine essential amino acids necessary for the human body.
No Nutritional Difference: For consumption, there is no practical or nutritional difference between fertile and infertile eggs regarding protein or overall health benefits.
Proteins Have Functional Roles: Specific proteins in the egg, such as ovalbumin and lysozyme, perform important functions beyond nutrition, including antimicrobial protection.

The Biological Basis for Protein in Unfertilized Eggs

All eggs laid by hens contain protein, whether they have been fertilized or not. A hen’s body is a biological marvel, designed to produce an egg, or ovum, on a near-daily cycle, regardless of the presence of a rooster. This process is dictated by light exposure and the hen’s internal cycle, not by mating. The egg's primary components, the yolk and the albumen (egg white), are created to provide all the necessary nutrients and protective elements for potential embryonic development. This means that every unfertilized egg is fully equipped with a rich and varied protein profile, a feature that makes it a nutritional powerhouse for human consumption as well. Most eggs found in grocery stores are unfertilized, produced by hens housed in controlled environments without roosters, and are perfectly safe and nutritious to eat.

The Breakdown: Protein in the Egg Yolk and Albumen

While the egg white often gets the credit for being a high-protein, low-fat food, the egg yolk also contains a substantial amount of protein. On a gram-for-gram basis, the yolk is denser in protein, though the larger volume of the egg white means it contributes more protein overall to a single egg. The protein composition varies significantly between the two parts, with each playing a vital role in the egg's complete nutritional makeup.

Comparing Protein Distribution: Egg White vs. Egg Yolk


Feature	Egg White (Albumen)	Egg Yolk (Vitellus)
Protein Content	Approx. 11% protein by weight.	Approx. 16% protein by weight.
Water Content	Approx. 88% water.	Approx. 48% water.
Primary Proteins	Ovalbumin, Ovotransferrin, Ovomucoid, Lysozyme.	Lipovitellins, Lipovitellinin, Phosvitin.
Protein-Related Function	Protective barrier, antimicrobial action, nutrient transport.	Nutrient storage, emulsifying properties.
Other Nutrients	Primarily water-soluble vitamins (e.g., riboflavin) and minerals.	Rich in fats, fat-soluble vitamins (A, D, E), and minerals.

What Specific Proteins Are Found in an Unfertilized Egg?

An unfertilized egg is a complex cocktail of hundreds of different proteins, each with a specific biological function. Some of the most notable proteins include:

Ovalbumin: The most abundant protein in the egg white, making up over half of its protein content. It is a phosphoglycoprotein that contributes significantly to the egg's nutritional value.
Ovotransferrin: Also found in the egg white, this protein has potent antimicrobial properties. It binds to metal ions, such as iron, making them unavailable for bacterial growth and thus protecting the egg.
Lysozyme: An enzyme present in the egg white that has the ability to break down the cell walls of bacteria, providing another layer of defense against microbial invaders.
Phosvitin: This protein is found in the egg yolk and plays a key role in protecting against lipid oxidation by binding to heavy metal ions.
Lipovitellins: These are high-density lipoproteins found in the yolk that contribute to the yolk's excellent emulsifying properties.

These proteins are all present from the moment the egg is formed within the hen. They exist to support potential life and provide a complete nutritional package, which remains intact whether or not fertilization occurs. The high biological value of egg protein, containing all nine essential amino acids, is the reason it is often used as a standard for measuring the quality of other food proteins.

Nutritional Value: Fertilized vs. Unfertilized

A common misconception is that fertilized eggs are more nutritious than unfertilized eggs. Numerous studies have shown that this is not the case; their nutritional content, including protein levels, is virtually identical. The only meaningful difference is the potential for a fertilized egg to develop into a chick if incubated properly. For a table egg that is meant for consumption, there is no difference in taste, appearance (apart from a very subtle visual marker on the yolk), or nutritional value. Therefore, consumers can rest assured that the unfertilized eggs they buy at the store offer the same high-quality protein as their fertile counterparts.

Conclusion

In summary, an unfertilized egg absolutely contains protein, and in significant amounts within both the egg white and the yolk. The presence of protein is a fundamental part of the egg's biological composition, designed to provide a rich source of nutrients for potential development. Proteins like ovalbumin, ovotransferrin, and phosvitin contribute to the egg's high biological value, antimicrobial defenses, and structural properties. The unfertilized eggs commonly sold for consumption have the same complete and high-quality protein profile as fertilized eggs, making them an excellent dietary source. For more in-depth information on the functions and bioactivity of egg proteins, authoritative research can be consulted through resources like the National Institutes of Health.

Frequently Asked Questions

Yes, grocery store eggs are almost always unfertilized but are a complete protein source, offering high-quality protein in both the egg white and yolk.

No, numerous studies have found that the nutritional content, including protein, is virtually identical between fertilized and unfertilized eggs.

Yes, a human ovum, like other animal eggs, is a biological cell that contains protein as a fundamental component of its cytoplasm and structures.

On a gram-for-gram basis, the yolk has a higher concentration of protein. However, because the egg white is much larger in volume, it contributes more total protein to a single egg.

The protein's primary function is to provide nutrients for potential embryonic development and protect the yolk from microbial attack. It serves as a reserve of essential amino acids.

Without incubation, it is very difficult. A fertilized egg has a small 'bullseye' (blastoderm) on its yolk, while an unfertilized egg has a less distinct white spot (blastodisc). This difference is very subtle.

No. Hens will lay eggs based on light cycles and their reproductive rhythm, regardless of whether a rooster is present. Most commercially produced eggs are unfertilized.