With aging, there is a progressive decline in total body water (TBW). Intracellular water (ICW) (inside the cells), parallel to an age-related loss of muscle mass and muscle strength. In the elderly population is at an increased risk of low-grade chronic dehydration, which could presumably affect muscle function and the individual’s functional capacity.

Loss of ICW with age is partially explained by not maintaining muscle mass but may also be due to a reduction in cell hydration. The fact that age-related muscle mass loss is responsible for only a small part of muscle weakening suggest that strength in older individuals is more related to muscle quality than to muscle quantity.

The concept that progressive age-related dehydration may be responsible for muscle function impairment and frailty.

Water has the following main function in the human body:

A metabolic function. Water is the medium in which all biochemical metabolism reactions occur. For example, the fact that each gram of muscle glycogen is stored with 27 grams of water allows glycogen to be easily attached by hydrolytic enzymes that quickly release glycogen which is the fuel for exercising muscles.

Water is also a transport function. Circulating blood is the transport system  that enables nutrients, hormones, oxygen, metabolites, etc. The process allows different organs and systems in the body to allow blood to filtrate by the kidneys to eliminate the waste products of metabolism through the urine.

Water also controls and maintain body temperature, regardless of the environmental temperature.

Water comes from three main sources: food, liquids and metabolism. Food contributes approximately 20% of total water inputs, while liquid provides 70-75%. There is great variability in the water intake recommendations of different international organizations. Read more about hydration on the elderly in the next article.