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Debunking the Myth of Avidin in Raw Eggs
Gastric juice exerts a strong denaturing effect on avidin, demonstrating that this protein is not structurally stable under physiological conditions. Avidin cannot be considered a conformationally resilient glycoprotein within the gastrointestinal tract: its biotin-binding capacity is highly dependent on physicochemical factors such as pH, temperature, light exposure, and the surrounding chemical environment. In the human stomach, these conditions lead to its near-complete inactivation.
Experimental data show that avidin loses functional activity at pH < 2.4, which corresponds to the acidity of human gastric juice. At around pH 1.8, it loses approximately 87–96% of its ability to bind biotin. This indicates profound denaturation and disruption of its ligand-binding properties. In real digestive conditions, avidin is therefore unable to effectively bind and sequester biotin, meaning it does not function as a meaningful antinutrient.
While *in vitro* avidin exhibits extremely high affinity for biotin (dissociation constant Kd ≈ 10⁻¹⁵ M), the situation *in vivo* is entirely different. In the acidic gastric environment at physiological temperature (37–38°C), and under the action of the proteolytic enzyme pepsin, avidin undergoes structural destabilization. Its tertiary structure unfolds, disulfide (S–S) bonds are disrupted, and the avidin–biotin complex becomes susceptible to enzymatic hydrolysis.
The same principle applies to protease inhibitors found in egg whites, such as ovomucoid, ovoinhibitor, ovomacroglobulin, and ovostatin. The latter three constitute only about 2% of total egg white protein and exhibit relatively weak inhibitory activity. Under gastric conditions, they are rapidly denatured and degraded.
Ovomucoid, although often cited as a trypsin inhibitor, is also sensitive to acidic and thermal conditions. In the highly acidic environment of the stomach, it loses its native structure and biological function. Even if raw egg whites are consumed, their inhibitory effects on digestive proteases diminish rapidly—within minutes of entering the stomach and small intestine.
Even with high intake (e.g., 10–20 raw egg whites), trypsin activity is reduced by only about 10–20%. In response, the pancreas compensates by increasing the secretion of trypsinogen, the inactive precursor of trypsin, thereby maintaining adequate proteolytic capacity in the diges
tive system.
Experimental data show that avidin loses functional activity at pH < 2.4, which corresponds to the acidity of human gastric juice. At around pH 1.8, it loses approximately 87–96% of its ability to bind biotin. This indicates profound denaturation and disruption of its ligand-binding properties. In real digestive conditions, avidin is therefore unable to effectively bind and sequester biotin, meaning it does not function as a meaningful antinutrient.
While *in vitro* avidin exhibits extremely high affinity for biotin (dissociation constant Kd ≈ 10⁻¹⁵ M), the situation *in vivo* is entirely different. In the acidic gastric environment at physiological temperature (37–38°C), and under the action of the proteolytic enzyme pepsin, avidin undergoes structural destabilization. Its tertiary structure unfolds, disulfide (S–S) bonds are disrupted, and the avidin–biotin complex becomes susceptible to enzymatic hydrolysis.
The same principle applies to protease inhibitors found in egg whites, such as ovomucoid, ovoinhibitor, ovomacroglobulin, and ovostatin. The latter three constitute only about 2% of total egg white protein and exhibit relatively weak inhibitory activity. Under gastric conditions, they are rapidly denatured and degraded.
Ovomucoid, although often cited as a trypsin inhibitor, is also sensitive to acidic and thermal conditions. In the highly acidic environment of the stomach, it loses its native structure and biological function. Even if raw egg whites are consumed, their inhibitory effects on digestive proteases diminish rapidly—within minutes of entering the stomach and small intestine.
Even with high intake (e.g., 10–20 raw egg whites), trypsin activity is reduced by only about 10–20%. In response, the pancreas compensates by increasing the secretion of trypsinogen, the inactive precursor of trypsin, thereby maintaining adequate proteolytic capacity in the diges
tive system.
