Water is vital for survival, and there is currently great interest in the benefits of good hydration for people to function well, and to look and feel good. The FSA currently recommends drinking about 1.2 litres per day (about 6–8 glasses). Thus it is very difficult to make generic recommendations about the amount of water to consume.

Individual water needs vary widely depending on many factors including body size and composition, the environment and levels of physical activity. Dental erosion occurs at a lower pH and is caused by the consumption of acidic foods and drinks, in particular, citrus juices and soft drinks containing acids. Dental caries are caused by a reduction in pH due to bacterial fermentation of carbohydrates, and so the frequency of consumption of drinks containing sugars is a concern for risk of caries. With regards to dental health, there are two concerns dental caries and dental erosion.

With obesity levels continuing to increase it is important for many in the population to control their energy intake, and drinks as well as foods must be considered for their energy content. The major concerns with regards to beverages are their energy content and their effect on dental health. All these can contribute to dietary water, but also have other effects on health both positive and negative. We also get water from all the drinks we consume, with the exception of stronger alcoholic drinks like wines and spirits. Food provides about 20% on average and this could vary widely depending on the types of food chosen. We can get water from almost all drinks and from some foods in the diet. It is also possible to consume too much water and in rare cases this can result in hyponatraemia (low levels of sodium in the blood). More mild dehydration (about 2% loss of body weight) can result in headaches, fatigue and reduced physical and mental performance. Extreme dehydration is very serious and can be fatal. However, if water losses are not sufficiently replaced, dehydration occurs. Generally, body water is maintained within narrow limits. The concentration of solutes (osmolality) in body fluids is closely controlled, and even very small changes in osmolality trigger a physiological response either to increase body water by reducing urinary output and stimulating thirst or to excrete excess water as urine. Water is the major component of body fluids, such as blood, synovial fluid (fluid in the joints), saliva and urine, which perform vital functions in the body. Water makes up a large proportion of our body weight (60% on average), distributed between the intracellular (inside cells) and extracellular (water in the blood and in between cells) compartments. Water is essential for life and maintaining optimal levels of hydration is important for humans to function well.

Foods that absorb water in body