Nutrient

A nutrient is any substance in food that the body uses to obtain energy, build tissue, or carry out chemical functions. Nutrients are found in food and drink; some cannot be synthesized by the body and must therefore be obtained from food.

In biology, nutrients are classified by the amount required. Nutrients needed in large quantities—such as carbohydrates, proteins, and fats—are called macronutrients. Those required in small quantities, such as vitamins and minerals, are called micronutrients. Water is also an essential component.

Macronutrients

Carbohydrates are the fastest source of energy; the body breaks them down into simple sugars like glucose. Proteins consist of amino acids, which are used to build muscle, enzymes, and hormones; some amino acids are essential, meaning they must be obtained from food. Fats provide concentrated energy and aid in the absorption of fat-soluble vitamins such as A, D, E, and K.

Micronutrients

Vitamins are natural substances that facilitate enzyme functions. They are divided into water-soluble vitamins (such as vitamin C and the B group) and fat-soluble vitamins. Minerals—such as iron, calcium, zinc, iodine, and potassium—are inorganic substances that participate in bone structure, oxygen transport, and the body's fluid and electrolyte balance.

Deficiency and excess

When a particular nutrient is lacking in food for prolonged periods, deficiency diseases can develop; for example, anemia caused by iron deficiency. Conversely, excessive intake of certain nutrients can cause harm, particularly fat-soluble vitamins and some minerals. For this reason, health recommendations are based on the advised daily limits for each nutrient.