Overview: A nutrient is a chemical element or compound that organisms use to sustain life. In animal and human contexts, nutrients supply energy, build and repair tissues, and support biochemical processes. The term encompasses substances that an organism either synthesizes itself or must obtain from food; those that cannot be made internally are called essential. For a general definition see chemical element or compound and for metabolic context see metabolism and physiology. This article focuses on nutrition in animals, especially humans; nutrition in bacteria and archaea is outside its scope.

Major categories and characteristics

Nutrients are commonly grouped by the amounts required and chemical nature. Macronutrients are needed in larger quantities and provide energy or structural components, while micronutrients are required in smaller amounts for enzymatic and regulatory roles. Nutrients may be organic (containing carbon, such as vitamins and amino acids) or inorganic (minerals, elements and water). A further practical distinction is between essential nutrients, which must be obtained from the diet, and nonessential nutrients, which the body can produce.

Key types and examples

  • Macronutrients: carbohydrates, proteins, and fats (lipids). They supply calories, provide building blocks like amino acids, and participate in cell membranes and signaling.
  • Micronutrients: vitamins and minerals. Vitamins are organic cofactors; minerals are inorganic elements such as iron, calcium and zinc important for structure and catalysis.
  • Water: often overlooked but essential for solvent functions, transport, temperature regulation, and chemical reactions.
  • Other important classes: essential fatty acids and essential amino acids, which cannot be synthesized in sufficient amounts and must come from food.

Roles, sources and bioavailability

Nutrients perform a range of roles: providing energy, forming and repairing tissues, enabling immune function, and supporting biochemical reactions. Dietary sources include plant and animal foods, fortified products, and supplements. The fraction of a nutrient absorbed and used by the body—bioavailability—depends on the food matrix, preparation methods, presence of enhancers or inhibitors (for example, vitamin C can enhance iron absorption; phytates can inhibit mineral uptake), and individual physiology.

Deficiency and excess: Insufficient intake of essential nutrients causes deficiency syndromes (such as anemia from low iron or scurvy from lack of vitamin C), while chronically excessive consumption can lead to toxicity (for example with fat‑soluble vitamins or some minerals). Public health recommendations and dietary reference values aim to balance adequacy with safety, though specific targets vary by age, sex, health status and life stage.

History and significance: Scientific understanding of nutrients developed over the 19th and 20th centuries as researchers distinguished macronutrients and identified vitamins and trace elements. This knowledge underpins modern fields such as dietetics, clinical nutrition and public health nutrition. In practice, awareness of nutrient types, food sources and interactions helps individuals and societies prevent deficiency diseases, manage chronic conditions, and plan balanced diets.

Distinctions and notable facts: Some nutrients are conditionally essential—normally synthesized but required from diet in certain situations (illness, infancy). Nutrient needs are context dependent: age, activity level, health and environment shape requirements. While this article centers on animals and humans, other kingdoms (plants, fungi, microbes) use different nutrient strategies and are discussed elsewhere.

For further technical or clinical details consult specialized texts or guidance from nutrition authorities and healthcare professionals.