How much water we really need depends on water functions and the mechanisms of daily water balance regulation. The aim of this review is to describe the physiology of water balance and consequently to highlight the new recommendations with regard to water requirements. Water has numerous roles in the human body. It acts as a building material; as a solvent, reaction medium and reactant; as a carrier for nutrients and waste products; in thermoregulation; and as a lubricant and shock absorber. The regulation of water balance is very precise, as a loss of 1% of body water is usually compensated within 24 h. Both water intake and water losses are controlled to reach water balance. Minute changes in plasma osmolarity are the main factors that trigger these homeostatic mechanisms. Healthy adults regulate water balance with precision, but young infants and elderly people are at greater risk of dehydration. Dehydration can affect consciousness and can induce speech incoherence, extremity weakness, hypotonia of ocular globes, orthostatic hypotension and tachycardia. Human water requirements are not based on a minimal intake because it might lead to a water deficit due to numerous factors that modify water needs (climate, physical activity, diet and so on). Water needs are based on experimentally derived intake levels that are expected to meet the nutritional adequacy of a healthy population. The regulation of water balance is essential for the maintenance of health and life. On an average, a sedentary adult should drink 1.5 l of water per day, as water is the only liquid nutrient that is really essential for body hydration.

BackgroundFew studies have examined plain water consumption among US adults. This study evaluated the consumption of plain water (tap and bottled) and total water among US adults by age group (20-50y, 51-70y, and ≥71y), gender, income-to-poverty ratio, and race/ethnicity.MethodsData from up to two non-consecutive 24-hour recalls from the 2005–2006, 2007–2008 and 2009–2010 National Health and Nutrition Examination Survey (NHANES) was used to evaluate usual intake of water and water as a beverage among 15,702 US adults. The contribution of different beverage types (e.g., water as a beverage [tap or bottled], milk [including flavored], 100% fruit juice, soda/soft drinks [regular and diet], fruit drinks, sports/energy drinks, coffee, tea, and alcoholic beverages) to total water and energy intakes was examined. Total water intakes from plain water, beverages, and food were compared to the Adequate Intake (AI) values from the US Dietary Reference Intakes (DRI). Total water volume per 1,000 kcal was also examined.ResultsWater and other beverages contributed 75-84% of dietary water, with 17-25% provided by water in foods, depending on age. Plain water, from tap or bottled sources, contributed 30-37% of total dietary water. Overall, 56% of drinking water volume was from tap water while bottled water provided 44%. Older adults (≥71y) consumed much less bottled water than younger adults. Non-Hispanic whites consumed the most tap water, whereas Mexican-Americans consumed the most bottled water. Plain water consumption (bottled and tap) tended to be associated with higher incomes. On average, younger adults exceeded or came close to satisfying the DRIs for water. Older men and women failed to meet the Institute of Medicine (IOM) AI values, with a shortfall in daily water intakes of 1218 mL and 603 mL respectively. Eighty-three percent of women and 95% of men ≥71y failed to meet the IOM AI values for water. However, average water volume per 1,000 kcal was 1.2-1.4 L/1,000 kcal for most population sub-groups, higher than suggested levels of 1.0 L/1.000 kcal.ConclusionsWater intakes below IOM-recommended levels may be a cause for concern, especially for older adults.

BackgroundFew studies have examined water consumption patterns among US children. Additionally, recent data on total water consumption as it relates to the Dietary Reference Intakes (DRI) are lacking. This study evaluated the consumption of plain water (tap and bottled) and other beverages among US children by age group, gender, income-to-poverty ratio, and race/ethnicity. Comparisons were made to DRI values for water consumption from all sources.MethodsData from two non-consecutive 24-hour recalls from 3 cycles of NHANES (2005–2006, 2007–2008 and 2009–2010) were used to assess water and beverage consumption among 4,766 children age 4-13y. Beverages were classified into 9 groups: water (tap and bottled), plain and flavored milk, 100% fruit juice, soda/soft drinks (regular and diet), fruit drinks, sports drinks, coffee, tea, and energy drinks. Total water intakes from plain water, beverages, and food were compared to DRIs for the US. Total water volume per 1,000 kcal was also examined.ResultsWater and other beverages contributed 70-75% of dietary water, with 25-30% provided by moisture in foods, depending on age. Plain water, tap and bottled, contributed 25-30% of total dietary water. In general, tap water represented 60% of drinking water volume whereas bottled water represented 40%. Non-Hispanic white children consumed the most tap water, whereas Mexican-American children consumed the most bottled water. Plain water consumption (bottled and tap) tended to be associated with higher incomes. No group of US children came close to satisfying the DRIs for water. At least 75% of children 4-8y, 87% of girls 9-13y, and 85% of boys 9-13y did not meet DRIs for total water intake. Water volume per 1,000 kcal, another criterion of adequate hydration, was 0.85-0.95 L/1,000 kcal, short of the desirable levels of 1.0-1.5 L/1,000 kcal.ConclusionsWater intakes at below-recommended levels may be a cause for concern. Data on water and beverage intake for the population and by socio-demographic group provides useful information to target interventions for increasing water intake among children.

articles ePiDeMiOlOGY IntroductIonData from short-term controlled experiments suggest that drinking water may promote weight loss. Drinking water vs. no beverage increases energy expenditure and rates of lipolysis (1-4). Drinking water instead of caloric beverages lowers total energy intake by eliminating beverage calories (5-16). Although absolute increases in drinking water may promote weight loss by altering metabolism, and relative increases in drinking water may promote weight loss by lowering total energy intake, no studies have tested for long-term effects of drinking water on changes in body weight or composition. It is unknown whether drinking water promotes weight loss over time under free-living conditions, independent of diet and activity, or whether water has benefits distinct from other unsweetened or noncaloric beverages.This study took advantage of data from the Stanford A TO Z weight loss intervention to determine whether increased intake of drinking water was associated with weight loss over 12 months in free-living women assigned to four popular weight loss diets. The study tested for absolute effects of increasing intake of drinking water to ≥1 l/day, as well as relative effects of replacing caloric beverages with drinking water on weight loss. Relative effects on weight loss were expected for this sample, because drinking water instead of sweetened caloric beverages was associated with lower total energy intake in A TO Z participants (17). Multivariable models were used to explore whether change in beverage calories might mediate observed associations, and whether unsweetened or noncaloric beverages might be associated with comparable benefit. Methods and ProceduresThe Stanford A TO Z study was a clinical weight loss trial that randomized overweight premenopausal women to four popular weight loss diets that are publicly available in book form: background: Data from short-term experiments suggest that drinking water may promote weight loss by lowering total energy intake and/or altering metabolism. The long-term effects of drinking water on change in body weight and composition are unknown, however. objective: This study tested for associations between absolute and relative increases in drinking water and weight loss over 12 months. Methods and Procedures: Secondary analyses were conducted on data from the Stanford A TO Z weight loss intervention on 173 premenopausal overweight women (aged 25-50 years) who reported <1 l/day drinking water at baseline. Diet, physical activity, body weight, percent body fat (dual-energy X-ray absorptiometry), and waist circumference were assessed at baseline, 2, 6, and 12 months. At each time point, mean daily intakes of drinking water, noncaloric, unsweetened caloric (e.g., 100% fruit juice, milk) and sweetened caloric beverages, and food energy and nutrients were estimated using three unannounced 24-h diet recalls. Beverage intake was expressed in absolute (g) and relative terms (% of beverages). Mixed models were used to test for effects of absolute and rela...

STOOKEY, JODI D., FLORENCE CONSTANT, CHRISTOPHER D. GARDNER, AND BARRY M. POPKIN. Replacing sweetened caloric beverages with drinking water is associated with lower energy intake. Obesity. 2007;15:3013-3022. Objective: Reduced intake of sweetened caloric beverages (SCBs) is recommended to lower total energy intake. Replacing SCBs with non-caloric diet beverages does not automatically lower energy intake, however. Compensatory increases in other food or beverages reportedly negate benefits of diet beverages. The purpose of this study was to evaluate drinking water as an alternative to SCBs. Research Methods and Procedures: Secondary analysis of data from the Stanford A TO Z intervention evaluated change in beverage pattern and total energy intake in 118 overweight women (25 to 50 years) who regularly consumed SCBs (Ͼ12 ounces/d) at baseline. At baseline and 2, 6, and 12 months, mean daily beverage intake (SCBs, drinking water, non-caloric diet beverages, and nutritious caloric beverages), food composition (macronutrient, water, and fiber content), and total energy intake were estimated using three 24-hour diet recalls. Beverage intake was expressed in relative terms (percentage of beverages). Results:In fixed effects models that controlled for total beverage intake, non-caloric and nutritious caloric beverage intake (percentage of beverages), food composition, and energy expenditure [metabolic equivalent (MET)], replacing SCBs with drinking water was associated with significant decreases in total energy intake that were sustained over time. The caloric deficit attributable to replacing SCBs with water was not negated by compensatory increases in other food or beverages. Replacing all SCBs with drinking water was associated with a predicted mean decrease in total energy of 200 kcal/d over 12 months. Discussion: The results suggest that replacing SCBs with drinking water can help lower total energy intake in overweight consumers of SCBs motivated to diet.