Processes of taking in and utilizing food substances. Food generates energy and supplies materials used in body tissues and processes. Calories are supplied by carbohydrates (sugars and starches), fats, and proteins. Other nutrients include minerals, vitamins, and dietary fibre. Minerals are used in many ways—iron for hemoglobin; calcium for bones, teeth, and cellular processes; sodium and potassium to regulate homeostasis, iodine to produce thyroid hormones. Trace minerals have functions that are less well-understood. Fibre is not broken down chemically in the body but aids digestion, lowers blood cholesterol, and may help prevent some cancers and hypertension. Different amounts of these nutrients exist in different foods; a varied diet ensures an adequate supply. Nutritional supplements, required by some people, do not compensate for an unhealthy diet. Sufficient water is always essential. Inadequate nutrient intake or absorption leads to malnutrition and disease.

This entry comes from Encyclopædia Britannica Concise.
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