Methylhistidine

Methylhistidine, specifically 3-methylhistidine, is a modified amino acid released when the muscle proteins actin and myosin are broken down during meat processing or digestion. It is frequently determined in meat and meat products as an indicator of connective tissue content and overall muscle-tissue composition, since its level tracks the proportion of true skeletal muscle versus other tissues. Meat scientists use it to check the composition of comminuted and restructured meats and to detect the substitution of cheaper non-muscle tissues, making it a useful authenticity marker in meat analysis. Because it is not metabolized further and is excreted unchanged, it also serves in nutrition research as a marker of muscle protein breakdown in the body.