Water is an essential nutrient - it is required in amounts that exceed the body's ability to produce it. All biochemical reactions occur in water. It fills the spaces in and between cells and helps form structures of large molecules such as protein and glycogen.
Most foods contain water. The body can usually get 20% of its total water requirements from solid foods alone. The human body can last weeks without food, but only days without water.
The digestion process also produces water as a byproduct and can provide around 10 per cent of the body’s water requirements.
Water is a transparent and nearly colorless chemical substance. Its chemical formula is H2O, meaning that its molecule contains one oxygen and two hydrogen atoms.
Water covers 71% of the Earth's surface. It is vital for all known forms of life. On Earth, 97% of the planet's crust water is found in seas and oceans, 1.7% in groundwater, 1.7% in glaciers and the ice caps. Only 2.5% of this water is freshwater, and 98.8% of that water is in ice (excepting ice in clouds) and groundwater. Less than 0.3% of all freshwater is in rivers, lakes.
Safe drinking water is essential to humans and other lifeforms even though it provides no calories or organic nutrients. ~One billion people still lack access to safe water. It was estimated that by 2025 more than half of the world population will be facing water-based vulnerability, and by 2030 water demand in some developing regions of the world will exceed supply by 50%.
Approximately 70% of the freshwater used by humans goes to agriculture.
Overnutrition, a type of malnutrition, is emerging with rates of obesity and related chronic diseases associated with urbanisation, aging populations, technological development and globalisation of food supplies and industry. Billions of dollars are spent annually by the food industry to promote the consumption of highly refined, high-calorie foods with little or no nutritional value.
At least 35 million overweight children are living in developing countries and 8 million in developed countries. Children are increasingly exposed to high-fat, high-sugar, high-salt, energy-dense, micronutrient-poor foods which tend to be cheaper than healthy foods. General imbalance in energy intake compared to physical activity levels is driving the obesity epidemic. In industrialised countries, child obesity risk is associated with lower household income, women with less education, and single parent households.
Obesity is increasingly prevalent among adolescent girls and women, as access to a greater quantity of inexpensive, tasty, and convenient foods increases.
Taxation on high-calorie, low-nutrition foods can play a significant role in reducing the consumption of such products. Population-wide weight-control campaigns that raise awareness among medical staff, policy-makers and the public at large can also help to reduce obesity. Particularly important is the promotion of health literacy. Additional measures include restrictions on the marketing of unhealthy foods and sugary drinks to children, and controls on the use of misleading health and nutrition claims; mandatory front-of-pack food labelling helps consumers to identify healthier options.