Nutritional needs are the quantities of energy, protein, essential fats, vitamins, minerals, and water that a person must consume to maintain health, growth, and bodily function. They vary with age, sex, body size, pregnancy, lactation, illness, and physical activity, which is why authorities publish reference values such as recommended daily intakes and dietary reference values rather than single universal numbers. Meeting needs is about patterns rather than perfection on any single day, since the body stores some nutrients and tolerates short-term shortfalls. Public health nutrition assesses whether populations meet their needs through dietary surveys and biomarker monitoring, then designs interventions, from fortification to supplementation programmes, where gaps appear. Individual needs are best assessed by registered dietitians, who account for medical conditions that standard tables cannot.