Water is essential for life,as all metabolic processes occur in a water medium.Since we can live only a few days without it,water is often referred to as the most essential nutrient.Dietary sources of water include the food we eat and the beverages (including water) that we drink.Our scientific understanding of the physiological process and the impact of hydration status on physical and mental performance is relatively new.Research and increased understanding of the importance of water consumption by military personnel was determined in the 1940s,but only recently has our understanding of hydration status on physical performance,cognitive function,and disease begtm to emerge.Many diseases are muhifactorial in origin.