What is the chemical composition of a human? Almost 99% of the mass of the human body is made up of six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Only about 0.85% is composed of another five elements: potassium, sulfur, sodium, chlorine, and magnesium. Compare our bodies to a mere plastic bag with the ingredients as stated above. Would it not be logical to assume food is important to the chemical reactions going on? Additionally pharmaceuticals (chemicals) are know to have adverse effects on the body. Split TMS standards would be believing one but not the other. This is the “BODY” side to the Mind Body Syndrome. PS. I never liked chemistry at school.