Which Enzymes Are Inhibited by Raw Eggs? Understanding Nutritional Inhibitors

December 22, 2025 •

2 min read

A study revealed that the human body absorbs only about 50% of the protein from raw eggs, compared to over 90% from cooked eggs. This inefficiency stems from specific anti-nutritional factors in the egg white, which is why it is important to understand which enzymes are inhibited by raw eggs and what the implications are for your health.

Quick Summary

Raw egg whites contain avidin, which binds biotin, and several protease inhibitors that hinder protein digestion. These factors reduce nutrient absorption, but cooking neutralizes them, significantly improving the bioavailability of both protein and biotin.

Key Points

Avidin: Raw egg white contains avidin, a protein that binds to biotin (vitamin B7) and prevents its absorption in the body.
Protease Inhibitors: Raw egg whites also contain protease inhibitors like ovomucoid that interfere with digestive enzymes such as trypsin, reducing protein digestibility.
Cooking Deactivates Inhibitors: The heat from cooking denatures both avidin and the protease inhibitors, neutralizing their anti-nutritional effects.
Improved Absorption: Cooking significantly increases protein digestibility from approximately 50% to over 90% and ensures that biotin is fully available for absorption.
Eliminates Salmonella Risk: Beyond enzyme inhibition, cooking also kills dangerous bacteria like Salmonella that can be present in raw eggs, preventing foodborne illness.

The Primary Enzyme Inhibitors in Raw Eggs

The enzymatic inhibition caused by raw eggs is primarily due to several key proteins found in the egg white, or albumen. These proteins act as natural defense mechanisms but can interfere with human digestion and nutrient absorption. The two main types of inhibitors are avidin and a group of protease inhibitors.

Avidin: The Biotin-Binding Protein

Raw egg white contains avidin, a protein with a strong affinity for biotin, also known as vitamin B7. Avidin binds tightly to free biotin in the digestive tract, creating a complex that cannot be digested or absorbed by the body. While a biotin deficiency is uncommon, consuming large amounts of raw egg whites over time could potentially lead to one, with symptoms including skin inflammation and hair loss.

Protease Inhibitors: Blocking Protein Digestion

Raw albumen also contains protease inhibitors like ovomucoid, ovoinhibitor, and ovostatin. These inhibitors interfere with digestive enzymes such as trypsin and chymotrypsin, which are essential for breaking down proteins into smaller, absorbable units in the small intestine. This inhibition reduces the efficiency of protein digestion and absorption. For example, protein absorption from raw eggs is around 50%, whereas cooked eggs offer about 91%.

The Crucial Role of Cooking

Cooking effectively neutralizes the anti-nutritional factors in raw eggs. Heat causes these protein structures to denature, deactivating the inhibitors and improving nutrient bioavailability.

Denaturation of Avidin: Heat disrupts the avidin-biotin bond, allowing for biotin absorption.
Denaturation of Protease Inhibitors: High temperatures break down protease inhibitors, facilitating protein digestion and making proteins more accessible to digestive enzymes.

Beyond Enzymes: The Salmonella Risk

Apart from enzyme inhibition, consuming raw eggs carries the risk of Salmonella contamination, a bacterium causing food poisoning with symptoms like diarrhea and fever.

Comparative Analysis: Raw vs. Cooked Eggs


Factor	Raw Eggs	Cooked Eggs
Biotin Bioavailability	Reduced; avidin binds biotin.	High; avidin is denatured by heat.
Protein Digestibility	Low (~50%); hindered by protease inhibitors.	High (~91%); inhibitors are denatured.
Protease Activity	Inhibited by ovomucoid, ovoinhibitor.	Optimal; inhibitors are deactivated.
Salmonella Risk	High; potential for bacterial contamination.	Negligible; bacteria are killed by heat.
Enzyme Denaturation	None (inhibitors are active).	Complete (inhibitors are neutralized).

Summary of Health Benefits from Cooking Eggs

Cooking eggs offers health benefits by deactivating natural inhibitors:

Maximized Protein Absorption: Denaturing protease inhibitors ensures efficient protein breakdown and absorption.
Full Biotin Availability: Heat releases biotin from avidin for better absorption.
Elimination of Foodborne Illness Risk: Cooking kills bacteria like Salmonella, making eggs safe, especially for vulnerable individuals.

Conclusion

Raw eggs contain anti-nutritional proteins like avidin and protease inhibitors that hinder the absorption of biotin and protein. Cooking neutralizes these inhibitors, unlocking the egg's full nutritional value. Considering both the nutritional drawbacks and the Salmonella risk, thoroughly cooked eggs are the safer and more beneficial choice. The FDA provides further guidance on food safety.

Frequently Asked Questions

While some people choose to, it is not recommended due to the risk of Salmonella bacterial contamination, which can cause severe food poisoning, and the reduced absorption of nutrients.

The primary substance is avidin, a protein found in raw egg white. Avidin binds to biotin and makes it unavailable for your body to absorb.

A biotin deficiency from raw egg consumption is rare and would require consuming a very large quantity of raw egg whites for a long period of time.

The heat from cooking denatures the protein structure of the inhibitors, such as avidin and ovomucoid. This permanently deactivates them and allows for proper nutrient absorption.

Studies have shown that your body can absorb up to 91% of the protein in cooked eggs, significantly higher than the 50% absorption rate from raw eggs.

The majority of the enzyme inhibitors, including avidin and ovomucoid, are concentrated in the egg white (albumen).

No. While raw eggs have the same nutritional content, the inhibitors present in raw egg white hinder absorption. Cooking neutralizes these inhibitors, making the nutrients more bioavailable.