A supplement is a product taken to add nutritional value missing — or thought to be missing — from the diet. The category covers vitamin and mineral pills, fish oil capsules, protein powders, herbal extracts, and probiotics, sold as tablets, capsules, powders, or drinks. People take them to correct deficiencies, support training, or pursue general health, and some groups genuinely need them: folic acid in pregnancy, vitamin D in northern winters, B12 for vegans. But supplements are not a substitute for a balanced diet, quality varies widely, and excessive doses of fat-soluble vitamins and minerals can be harmful. In most countries they are regulated as foods rather than medicines, with lighter oversight.