Human nutrition refers to the provision of essential nutrients necessary to support human life and health. Generally, people can survive up to 40 days without food, a period largely depending on the amount of water consumed, stored body fat, muscle mass and genetic factors.
Poor nutrition is a chronic problem often linked to poverty, poor nutrition understanding and practices, and deficient sanitation and food security. Malnutrition and its consequences are immense contributors to deaths and disabilities worldwide. Promoting good nutrition helps children grow, promotes human development and eradication of poverty.
The seven major classes of nutrients are carbohydrates, fats, fiber, minerals, proteins, vitamins, and water. These nutrient classes are categorized as either macronutrients or micronutrients (needed in smaller quantities). The macronutrients are carbohydrates, fats, fiber, proteins, and water. The micronutrients are minerals and vitamins.The macronutrients (excluding fiber and water) provide structural material (amino acids from which proteins are built, and lipids from which cell membranes and some signaling molecules are built), and energy. Some of the structural material can be used to generate energy internally.
Vitamins, minerals, fiber, and water do not provide energy, but are required for other reasons. A third class of dietary material, fiber (i.e., nondigestible material such as cellulose), seems also to be required, for both mechanical and biochemical reasons, though the exact reasons remain unclear. For all age groups, males need to consume higher amounts of macronutrients than females. In general, intakes increase with age until the second or third decade of life.