Compared with Raw Bovine Meat, Boiling but Not Grilling, Barbecuing, or Roasting Decreases Protein Digestibility without Any Major Consequences for Intestinal Mucosa in Rats, although the Daily Ingestion of Bovine Meat Induces Histologic Modifications in the Colon
Résumé
Background: Cooking may impair meat protein digestibility. When undigested proteins are fermented by the colon
microbiota, they can generate compounds that potentially are harmful to the mucosa.
Objectives: This study addressed the effects of typical cooking processes and the amount of bovine meat intake on the
quantity of undigested proteins entering the colon, as well as their effects on the intestinal mucosa.
Methods: Male Wistar rats (n = 88) aged 8 wk were fed 11 different diets containing protein as 20% of energy. In 10 diets,
bovine meat proteins represented 5% [low-meat diet (LMD)] or 15% [high-meat diet (HMD)] of energy, with the rest as
total milk proteins. Meat was raw or cooked according to 4 processes (boiled, barbecued, grilled, or roasted). A meat-free
diet contained only milk proteins. After 3 wk, rats ingested a 15N-labeled meat meal and were killed 6 h later after receiving
a 13C-valine injection. Meat protein digestibility was determined from 15N enrichments in intestinal contents. Cecal shortand
branched-chain fatty acids and hydrogen sulfide were measured. Intestinal tissues were used for the assessment of
protein synthesis rates, inflammation, and histopathology.
Results:Meat protein digestibility was lower in rats fed boiled meat (94.5%6 0.281%) than in the other 4 groups (97.5%6
0.0581%, P < 0.001). Cecal and colonic bacterial metabolites, inflammation indicators, and protein synthesis rates were
not affected by cooking processes. The meat protein amount had a significant effect on cecal protein synthesis rates
(LMD > HMD) and on myeloperoxidase activity in the proximal colon (HMD > LMD), but not on other outcomes. The
ingestion of bovine meat, whatever the cooking process and the intake amount, resulted in discrete histologic
modifications of the colon (epithelium abrasion, excessive mucus secretion, and inflammation).
Conclusions: Boiling bovine meat at a high temperature (100C) for a long time (3 h) moderately lowered protein
digestibility compared with raw meat and other cooking processes, but did not affect cecal bacterial metabolites related to
protein fermentation. The daily ingestion of raw or cooked bovine meat had no marked effect on intestinal tissues, despite
some slight histologic modifications on distal colon.