Water

Water is a naturally occurring compound (H₂O) that makes up approximately 50–70% of adult body weight. It is sourced from tap water, bottled water, mineral water, and water naturally present in foods and beverages. In culinary and food manufacturing contexts, water serves as a solvent, cooking medium, ingredient in beverages, and component in processed foods.

Water has no calories, proteins, fats, or carbohydrates. It is absorbed passively in the small intestine and colon, where it aids in nutrient absorption and stool formation. Adequate hydration supports optimal gut motility and helps prevent constipation; insufficient water intake can lead to harder stools and reduced digestive efficiency.

Thermoregulation and Physical Function

Water participates directly in thermoregulation through perspiration and respiration. It maintains plasma volume and blood pressure, supports oxygen transport to tissues, and enables metabolic reactions. Daily water needs vary based on age, sex, activity level, and climate, but standard guidance suggests around 2–3 liters per day for healthy adults—though individual requirements differ.

Hydration Status and Intake Guidance

Most healthy people tolerate water well across a wide range of intakes; the kidneys excrete excess water efficiently. However, consuming several liters of water in a short period without adequate electrolyte intake can dilute blood sodium and cause hyponatremia (low blood sodium), a potentially serious condition—though this is rare in normal eating patterns. People with kidney disease, heart failure, or certain endocrine conditions should follow medical guidance on fluid intake. Thirst is a reliable indicator of hydration need for most individuals; urine color (pale yellow suggests adequate hydration) is a practical marker.