<prompt> The estimation of 3 methyl histidine in urine is used to study -Status of folate in the bodyRenal diseaseSkeletal muscleProtein absorption in the gut  <response>: 3-Methylhistidine 3-MH is a post-translationally modified amino acid which is excreted in human urine. Urinary concentrations of 3-methylhistidine serve as a reliable index of skeletal muscle protein breakdown in humans who have been subject to muscle injury. Ref Davidson 23rd edition pg 981 