The inadequate incorporation of digested nutrients, such as proteins, minerals, and vitamins, into body tissues including bone, muscle, and organs. While malabsorption describes failure to take nutrients up from the gut, malassimilation is the broader failure to utilise them for building and maintaining the body, whether because of poor absorption, metabolic defects, chronic disease, or hormonal disturbances. In children it manifests as stunted growth and poor development; in adults as muscle wasting, fragile bones, and impaired healing. Addressing it requires correcting the underlying disorder alongside optimised nutrition, ensuring that nutrients consumed are actually converted into healthy tissue.