Nutrients

Nutrients are substances required by living organisms to sustain life, growth, and health. In humans, nutrients are obtained from foods and beverages and are typically grouped into macronutrients and micronutrients, with additional dietary components such as fiber and water that influence nutrition.

Macronutrients supply energy and serve as building blocks. Carbohydrates provide about 4 kcal per gram and are a primary energy source; proteins also yield 4 kcal/g and supply amino acids for tissue maintenance and enzyme production; fats supply about 9 kcal/g and support energy storage, cell function, and the absorption of fat-soluble vitamins. Water is essential for hydration, circulation, temperature regulation, and numerous bodily reactions, while dietary fiber supports gut health and digestion though it is not digested for energy.

Micronutrients include vitamins and minerals required in smaller amounts but are essential for metabolism, immunity, growth, and structural functions. Examples include vitamin C, iron, calcium, iodine, and zinc. Many micronutrients act as cofactors for enzymes or antioxidants that protect cells from damage. Some nutrients have specific bioavailability patterns influenced by food matrices, preparation, and interactions with other nutrients.

Essential versus non-essential: essential nutrients must be supplied by the diet because the body cannot produce enough amounts, whereas non-essential nutrients can be synthesized internally. Some nutrients are conditionally essential under certain life stages or health conditions. Absorption and utilization depend on form, host factors, and overall dietary context.

A balanced diet from a variety of foods—fruits, vegetables, grains, legumes, dairy or fortified substitutes, and appropriate protein sources—helps ensure adequate intake of both macro- and micronutrients, supporting health and reducing the risk of nutrient-related disorders.