Water is the most important nutrient. Total body water comprises approximately 45-75% of a person’s body weight (Reibl, 2013). Water is important for a number of functions in the body. It delivers oxygen to cells, transports nutrients, removes wastes and flushes toxins, lubricates joints, regulates body temperature, and helps maintain normal electrical properties of cells. The body can produce only about 8% of the water it needs through metabolic processes. The remaining 92% must be obtained through the foods and beverages we consume. The body cannot actually store water, making daily consumption important for healthy function. In addition to consuming enough water, it’s also crucial to get enough electrolytes as well so our bodies can make proper use of the water.

Even though total fluid intake has actually increased among US adults from 79 fluid ounces in 1989, to 100 fluid ounces in 2002, water is actually one of the most common nutritional deficiencies (Popkin, 2010).  Unfortunately, this increase is mostly due to the increased consumption of caloric beverages, many of which contain large amounts of dehydrating sugar and caffeine.  Populations with an increased risk for dehydration include children, especially black and Hispanic children, older adults, and those of a lower socioeconomic status. These populations are especially vulnerable to heat stress and dehydration related issues with thermoregulation. Additionally, elderly people are less thirsty and tend to drink less fluids. Dehydration can cause fatigue, headaches, altered thermoregulatory capability, and cognitive impairments such as visual perception, short-term memory, and psychomotor ability. Recent literature suggests that as little as a loss of 1-2% body water can impair cognitive performance (Reibl, 2013).  In the elderly and very ill, dehydration is also a risk-factor for delirium and delirium presenting as dementia. In this population, fluid intake and water homeostasis can be complicated by disease, dementia, incontinence, renal insufficiency, restricted mobility, and medication side effects. Adequate water intake is also important for normal gastrointestinal and kidney function, and plays an important role in hemodynamic response.

Water needs vary from person to person, so developing a recommended dietary allowance is difficult. On average, Americans typically only consume about 4 cups of drinking water a day (Reibl, 2013). However, a good rule is to consume at least the number of ounces equal to half your body weight in pounds, and even more if you’re drinking dehydrating beverages such as caffeinated drinks, soda, or fruit juices, or taking medications that cause a diuretic effect. A health professional must consider a person’s level of physical activity, environment, and other health conditions when assessing hydration status. Although over consumption of caffeinated beverages can cause dehydration, there is some good news for coffee drinkers. A recent study found no evidence of dehydration with moderate daily coffee intake.  In a cross-over analysis, Killer et al. found that habitual coffee consumers actually experienced less of a diuretic effect from coffee consumption than caffeine naïve subjects. They also observed no significant difference in total body water between coffee drinkers and non-coffee drinkers.

To ensure adequate hydration, it is important to drink properly sourced, filtered water and supplement with electrolytes especially when sweating or exercising. Drink to thirst, but aim for a minimum number of ounces equal to half your body weight in pounds. Avoid sugared beverages and consume only small amounts of caffeine, and add 1.5 times the amount of water to compensate for any de-hydrating beverages.

Killer, Sophie C, Blannin, Andrew K, Jeukendrup, Asker E. (2014). No Evidence of Dehydration with Moderate Daily Coffee Intake: A Counterbalanced Cross-Over Study in a Free-Living Population. Plos One. Volume 9 Issue 1. Retrieved from https://doi.org/10.1371/journal.pone.0084154.

Popkin, Barry M, D’Anci, Kristen E, and Rosenberg, Irwin H. (2010) Water, hydration, and health. Nutrition Reviews Volume 68, Issue 8, 1 August 2010, Pages 439–458. Retrieved from https://doi.org/10.1111/j.1753-4887.2010.00304.x.

Riebl, S. K., & Davy, B. M. (2013). The Hydration Equation: Update on Water Balance and Cognitive Performance. ACSM’s health & fitness journal, 17(6), 21–28. doi:10.1249/FIT.0b013e3182a9570f.