What consumption of raw eggs can inhibit the absorption of?

December 22, 2025 •

3 min read

In 1926, researchers discovered that excessive consumption of raw egg whites could cause a condition known as "egg-white injury syndrome" in rats. This syndrome, which includes severe dermatitis and hair loss, is a direct result of how raw eggs can inhibit the absorption of the water-soluble B vitamin, biotin.

Quick Summary

Raw egg whites contain avidin, a protein that binds tightly to biotin, a B vitamin, preventing its absorption in the intestines. This effect is neutralized by heat, making cooked eggs a safe and highly nutritious food source. Concerns about raw eggs also include a significant risk of bacterial contamination like Salmonella.

Key Points

Biotin Absorption Inhibited: Raw egg whites contain avidin, a protein that binds tightly to the B vitamin biotin, preventing its absorption in the body.
Cooking Deactivates Avidin: Heat denatures the avidin protein, meaning cooking eggs completely eliminates the risk of inhibited biotin absorption.
Food Safety Risk: Raw eggs pose a serious risk of bacterial contamination from Salmonella, which is a major food safety concern.
Cooked Eggs are Safer: Thoroughly cooking eggs kills harmful bacteria, making them safer to eat and eliminating the food poisoning risk.
Improved Protein Digestion: Some studies suggest that the protein in cooked eggs is more bioavailable and easily absorbed by the body than in raw eggs.
Deficiency Requires High Intake: A biotin deficiency from raw eggs is unlikely unless a person consumes a very large number of raw egg whites over an extended period.
Yolks Contain Biotin: The yolk of an egg is a good source of biotin, but the avidin in the raw white cancels this benefit out if consumed raw.

The Science Behind Biotin Inhibition

The primary reason that consuming raw eggs can inhibit the absorption of certain nutrients lies in a protein called avidin, found exclusively in the egg white. Avidin has an extremely high binding affinity for the B vitamin biotin, also known as vitamin B7. When raw egg whites are ingested, the avidin binds irreversibly to any biotin present in the digestive tract, forming a large, indigestible complex. This complex cannot be absorbed by the small intestine and is subsequently passed out of the body.

Unlike in some nutritional myths, the egg yolk is actually a rich source of biotin, which is what led to confusion in the past. However, the avidin in the raw egg white effectively nullifies the biotin benefits from the yolk when the whole egg is consumed raw. The good news is that avidin is heat-labile, meaning it is destroyed by cooking. When eggs are cooked, the avidin protein denatures and loses its ability to bind to biotin, allowing the body to absorb the vitamin freely. For a biotin deficiency to occur in a healthy individual, a person would need to consume large quantities of raw egg whites—on the order of a dozen or more—daily over an extended period.

Other Nutritional Concerns with Raw Egg Consumption

Beyond the specific effect on biotin, there are other reasons to favor cooked eggs over raw ones. These include potential issues with overall protein absorption and, more critically, the risk of bacterial contamination.

Protein Bioavailability: One older study on a very small group of people suggested that the body might only absorb about 50% of the protein from raw eggs, compared to roughly 90% from cooked eggs. While the evidence is limited, it indicates that cooking may make the proteins more accessible for digestion and absorption.
Food Safety Risks: The most significant and immediate danger associated with eating raw or undercooked eggs is the risk of contamination with Salmonella bacteria. Salmonella infection can cause severe food poisoning with symptoms like diarrhea, fever, and abdominal cramps. In vulnerable populations, such as young children, the elderly, or those with compromised immune systems, it can lead to serious, life-threatening complications. Cooking eggs thoroughly is the most effective way to kill harmful bacteria and eliminate this risk.

Symptoms of Biotin Deficiency

Although rare in healthy individuals, excessive consumption of raw egg whites can lead to a biotin deficiency over time. The symptoms develop gradually and can affect various bodily systems.

Skin: Scaly, red rashes, particularly around the eyes, nose, and mouth.
Hair: Thinning hair or hair loss (alopecia).
Nails: Brittle, thin, or ridged nails prone to breaking.
Nervous System: Neurological symptoms can include depression, lethargy, hallucinations, and numbness or tingling in the extremities.
Muscles: Generalized weakness and muscle pain.

Raw vs. Cooked Eggs: A Comparison


Feature	Raw Eggs (Whites and Yolks)	Cooked Eggs (Whites and Yolks)
Biotin Absorption	Inhibited by avidin in the raw egg white, as it binds to biotin.	Enhanced due to avidin denaturing during cooking, allowing biotin absorption.
Protein Digestion	Potentially lower bioavailability; some studies suggest around 50% absorption.	Protein is more readily absorbed; studies indicate about 90% absorption.
Salmonella Risk	Present and a significant food safety concern, especially with unpasteurized eggs.	Eliminated when cooked thoroughly, significantly reducing the risk of food poisoning.
Avidin Status	Active and binds to biotin.	Inactivated by heat, rendering it harmless.

Conclusion

While raw eggs are sometimes associated with fitness and bodybuilding, the scientific evidence points towards the clear benefits of consuming cooked eggs. The primary nutrient affected is biotin, which is inhibited by the protein avidin in raw egg whites. This effect is completely neutralized by cooking. Furthermore, the risk of bacterial contamination like Salmonella and the potential for reduced protein absorption make cooked eggs the safer and more nutritionally beneficial choice. To gain maximum nutritional value and ensure food safety, always cook your eggs thoroughly before eating them.

Resources

For more information on biotin and dietary nutrients, consult the National Institutes of Health (NIH) Office of Dietary Supplements website: https://ods.od.nih.gov/factsheets/Biotin-HealthProfessional/.

Frequently Asked Questions

Raw egg whites contain a protein called avidin that binds to biotin in the small intestine. This binding creates a complex that the body cannot absorb, thus preventing biotin from being utilized.

Yes, cooking an egg denatures the avidin protein in the egg white. This destroys its ability to bind to biotin, allowing the vitamin to be absorbed normally when the egg is cooked.

It is highly unlikely to cause a biotin deficiency from moderate consumption. It would typically require consuming an excessive number of raw egg whites daily over many months to cause a deficiency.

The most significant health risk is contamination with Salmonella bacteria, which can cause severe food poisoning. Cooking eggs is the best way to eliminate this risk.

Pasteurized eggs have been treated to reduce the risk of Salmonella contamination, making them a safer option for use in recipes that call for raw eggs. However, the avidin that inhibits biotin absorption is still present unless they are cooked.

Avidin is found exclusively in the egg white (albumen). The yolk, conversely, is a good source of biotin itself.

Some limited research suggests that protein absorption might be less efficient with raw eggs compared to cooked eggs. For example, protein absorption was found to be lower in a small study of raw versus cooked eggs.

Symptoms of a deficiency include hair thinning, a scaly red rash, and brittle nails. In severe, rare cases, it can cause neurological symptoms like lethargy and depression.

Biotin is found in many foods, including organ meats (liver), nuts and seeds, legumes (lentils, soybeans), and certain vegetables like sweet potatoes and mushrooms.