What is the anti vitamin in raw eggs?

December 22, 2025 •

5 min read

According to research from the National Institutes of Health, raw egg whites contain the protein avidin, which binds tightly to the vitamin biotin and prevents its absorption by the body. This is the "anti-vitamin" effect found in raw eggs, though it is easily neutralized through proper cooking methods.

Quick Summary

The anti-vitamin in raw eggs is avidin, a protein found in the egg white that binds to and inhibits the absorption of biotin, or vitamin B7. Cooking denatures avidin, rendering it inactive and allowing for proper biotin absorption. Excessive consumption of raw eggs over prolonged periods can potentially lead to biotin deficiency, but this is a rare occurrence. Cooking also eliminates the more significant risk of bacterial contamination, such as Salmonella.

Key Points

Avidin Binds Biotin: Raw egg whites contain avidin, a protein that forms a strong bond with biotin (vitamin B7), preventing its absorption by the body.
Cooking Deactivates Avidin: Heating eggs denatures avidin, destroying its biotin-binding ability and allowing for proper vitamin absorption.
Risk of Deficiency is Low but Possible: While most healthy individuals won't get a deficiency, consuming a large number of raw egg whites over a long period can lead to biotin deficiency symptoms.
Salmonella is the Greater Risk: Beyond avidin, the primary danger of raw eggs is contamination with Salmonella bacteria, which cooking effectively eliminates.
Cooked Eggs are More Bioavailable: Cooking eggs not only makes them safe but also improves the digestibility and absorption of their high-quality protein.
Certain Groups at Higher Risk: Pregnant women, young children, older adults, and those with compromised immune systems should never consume raw or undercooked eggs.
Pasteurization is a Safe Alternative: For recipes requiring raw eggs, pasteurized egg products can be used safely, as the heat treatment neutralizes avidin and kills bacteria.

The anti-vitamin effect in raw eggs is caused by a potent protein called avidin, found exclusively in the egg white. Avidin’s main function is to bind with the water-soluble B-vitamin biotin, also known as vitamin B7 or vitamin H. When avidin binds to biotin, it forms a complex that is not broken down by digestive enzymes, effectively preventing the body from absorbing the vitamin. While avidin is a significant concern for those who consume large quantities of raw egg whites over a long period, it is easily deactivated by heat, making cooked eggs a safe and healthy food choice.

Avidin and its Effect on Biotin Absorption

Avidin is a glycoprotein, meaning it is a protein with sugar molecules attached. It binds to biotin with one of the strongest non-covalent interactions known in nature. The biological purpose of avidin in eggs is believed to be an antibacterial defense mechanism, as bacteria require biotin to grow and the avidin in the egg white starves them of this essential nutrient.

The binding of avidin to biotin happens in the small intestine. Because the avidin-biotin complex is so stable and resistant to digestive enzymes, the biotin remains locked and is excreted from the body rather than being absorbed. This is why eating excessive raw eggs, particularly the whites, can lead to a biotin deficiency, also known as "egg white injury". It's important to note, however, that the egg yolk contains a substantial amount of biotin, which can partially offset the avidin in the white.

The Role of Cooking in Neutralizing Avidin

Cooking is the key to deactivating avidin and ensuring that the biotin in eggs is available for absorption. Heat denatures the avidin protein, destroying its unique three-dimensional structure and its ability to bind to biotin. Different cooking methods affect avidin neutralization in varying degrees:

Hard-Boiling: This method involves prolonged, high heat exposure, ensuring that the avidin in the egg white is completely denatured and inactivated.
Frying and Poaching: Studies have shown that residual avidin activity can remain in undercooked egg whites, especially in "cold spots". To be safe, eggs should be cooked until both the yolk and white are firm.
Pasteurization: Many liquid egg products and some in-shell eggs are pasteurized, a heating process that kills bacteria and also effectively denatures avidin.

Biotin Deficiency: Symptoms and Risks

While true biotin deficiency from consuming raw eggs is rare and requires an exceptionally high intake over a prolonged period, the symptoms can be severe. In most healthy individuals with a mixed diet, biotin intake is typically adequate. However, those who regularly consume large amounts of raw egg white may experience:

Hair thinning, hair loss, and brittle nails
Scaly, red rash around the eyes, nose, mouth, and perineum
Neurological symptoms such as depression, lethargy, hallucinations, or numbness and tingling in the extremities
Conjunctivitis (inflammation of the eye)
Metabolic abnormalities, such as lactic acidosis

These symptoms can be reversed with biotin supplementation and stopping the consumption of raw egg white.

Comparison of Raw vs. Cooked Eggs


Feature	Raw Eggs	Cooked Eggs
Avidin Activity	Active in the white, binds to and inhibits biotin absorption.	Denatured and inactive, allowing for full biotin absorption.
Biotin Absorption	Reduced due to avidin binding, especially with high, frequent consumption.	Full bioavailability, ensuring the body absorbs all available biotin.
Protein Absorption	Can be lower; a small, older study found only 50% absorption compared to 90% in cooked eggs.	Protein is easily digested and absorbed, maximizing its nutritional value.
Salmonella Risk	High risk of bacterial contamination, which can cause food poisoning.	Risk of Salmonella is eliminated once eggs are cooked to a safe temperature.
Key Nutrients	Contains important vitamins, minerals, and healthy fats, but absorption of some nutrients may be hindered.	All nutrients, including choline, lutein, and zeaxanthin, are readily available and easily absorbed.
Overall Safety	Never fully safe to consume due to avidin and Salmonella risks.	The safest way to consume eggs, eliminating the risk of foodborne illness.

Conclusion

In summary, the anti-vitamin in raw eggs is avidin, a protein that interferes with the body's absorption of the B-vitamin biotin. While the risk of a true biotin deficiency from raw egg consumption is low for most people, the more immediate danger is contracting foodborne illnesses like Salmonella. Cooking is the simple solution to both problems, as it denatures avidin and kills harmful bacteria. A thoroughly cooked egg offers the full nutritional benefits of its protein, vitamins, and minerals without any risk of antinutrient activity. For recipes calling for raw or undercooked eggs, using pasteurized egg products is the safest alternative.

Raw Eggs: A Dangerous Nutritional Gamble

Many people, including some athletes and bodybuilders, believe that consuming raw eggs offers superior nutritional benefits. However, this is a dangerous misconception. The risk of Salmonella contamination alone is enough to deter raw consumption, as this bacterium can lead to severe gastrointestinal distress, and in rare cases, life-threatening infections. The added interference with biotin absorption only detracts further from the perceived benefits. Additionally, research suggests that protein from cooked eggs is absorbed more efficiently by the body than protein from raw eggs, debunking the idea that raw is nutritionally superior. The best way to enjoy eggs is to cook them thoroughly, making them both safe and more bioavailable for your body.

For People with High Risk of Complications

Certain populations are at a significantly higher risk for serious illness from foodborne bacteria and should strictly avoid raw or undercooked eggs. This includes pregnant women, young children, older adults, and individuals with weakened immune systems. For these groups, using pasteurized eggs in recipes that call for raw eggs (like certain dressings or desserts) is a necessary safety precaution. Cooking eggs completely until the yolk and white are firm is the only way to guarantee safety from Salmonella.

Beyond Avidin: Other Considerations

Beyond the avidin and Salmonella risks, there is also the issue of protein absorption. As noted in the comparison table, your body may not be able to absorb all the high-quality protein from a raw egg as effectively as from a cooked one. The act of cooking breaks down the egg's proteins, making them more digestible. This means that for anyone looking to maximize their protein intake, cooking eggs is the more effective preparation method. Considering all the risks and inefficiencies of raw egg consumption, there is little compelling reason to forgo the simple and effective step of cooking.

Frequently Asked Questions

The specific anti-vitamin is a protein called avidin, found in raw egg whites. It has a high affinity for biotin and binds to it, preventing its absorption in the intestines.

It is highly unlikely for a typical person to develop a biotin deficiency from eating raw eggs occasionally. It would require consuming large amounts of raw egg whites daily over a prolonged period for a deficiency to occur.

Yes, cooking eggs thoroughly denatures the avidin protein, effectively destroying its ability to bind with biotin and making the vitamin fully available for absorption.

The most significant risk of consuming raw eggs is contamination with Salmonella bacteria, which can cause severe food poisoning, particularly in vulnerable populations.

Neither is safe to eat raw. While the avidin is in the white, the risk of Salmonella can be present in the yolk or on the shell. Cooking is the safest method for consuming eggs.

Yes, pasteurized eggs are a safe alternative for recipes that call for raw eggs. The pasteurization process uses heat to kill bacteria and also inactivates the avidin.

The most effective way to prevent the anti-vitamin effect of avidin is to cook your eggs thoroughly until both the yolk and white are firm. This heat treatment neutralizes the avidin.