Digestibility of cooked and raw egg protein in humans as assessed by stable isotope techniques.
Level 2 - randomized trial
Randomized crossover clinical trial
PubMed 9772141 · doi:10.1093/jn/128.10.1716
What was done
Five ileostomy patients were studied in a crossover design after ingesting a 25 g test meal of 13C- and 15N-labeled egg protein, once in cooked form and once in raw form. Ileal effluents were analyzed for 15N to calculate true ileal digestibility, and breath samples were analyzed for 13C excretion at regular intervals.
What was found
The true ileal digestibility was 90.9 ± 0.8% for cooked egg protein versus 51.3 ± 9.8% for raw egg protein. Breath 13C recovery was negatively correlated with the recovery of exogenous nitrogen in ileal effluents (r = -0.92, P < 0.001).
Why it matters
This study provides direct human quantitative evidence that cooking roughly doubles the ileal digestibility and net assimilation of dietary egg protein compared to consuming it raw.
Limits
The sample size is very small (n = 5). The study was conducted entirely in individuals with an ileostomy, which may alter transit or digestive dynamics compared to healthy individuals with an intact colon. The abstract does not evaluate different preparation styles or cooking times.
Cited by
- supports Boiling or cooking eggs denatures the protein and leads to faster release of amino acids into the circulation compared to consuming raw eggs.