nutrition

Nutrition is the science of how the body uses food to maintain health, energy, growth, and reproduction. It covers the intake, digestion, absorption, transport, and metabolism of nutrients, and the effects of dietary patterns on health. Nutrients are classified as macronutrients, which supply energy and building blocks, and micronutrients, which support metabolic processes. Water is essential for hydration, digestion, and circulation. Essential nutrients include certain amino acids, fatty acids, vitamins, and minerals that the body cannot synthesize in sufficient amounts.

Macronutrients provide energy: carbohydrates, fats, and proteins. Carbohydrates and fats yield calories, while proteins supply amino acids for tissue repair, immune function, and enzyme production. Dietary fiber contributes to gut health but is not used for energy by the body in the same way. Micronutrients, including vitamins and minerals, support metabolism, immunity, and tissue function. Adequate hydration is necessary for most physiological processes.

Nutrition science also considers energy balance and nutrient density, balancing calories with physical activity. Dietary guidelines emphasize a varied diet rich in fruits, vegetables, whole grains, lean proteins, and healthy fats, while limiting added sugars, sodium, and saturated fats. Nutritional needs vary by age, sex, activity level, health status, and life stage.

Public health nutrition addresses malnutrition in all forms, including undernutrition and overnutrition, and issues such as food safety, accessibility, and sustainability. Research uses controlled trials and observational studies to inform policy, guidelines, and individual choices, while food systems and cultural factors shape dietary patterns.