Water Researchers Do Not Have a Strategic Plan for Gathering Evidence to Inform Water Intake Recommendations to Prevent Chronic Disease
Abstract
:1. Confusion about How Much Water to Drink Has Persisted for Decades
2. U.S. Water Intake Recommendations Are Evidence-Based
2.1. Definition
“evidence is insufficient to establish water intake recommendations as a means to reduce the risk of chronic diseases. Instead an Adequate Intake (AI) for total water is set to prevent deleterious, primarily acute, effects of dehydration, which include metabolic and functional abnormalities.”[12] (p. 93)
“Daily water intake must be balanced with losses in order to maintain total body water. Body water deficits challenge the ability to maintain homeostasis during perturbations (e.g., sickness, physical exercise, and environmental exposure) and can affect function and health.”[12] (p. 94)
“Over the course of a few hours, body water deficits can occur due to reduced intake or increased water losses from physical activity and environmental (e.g., heat) exposure. However, on a day to day basis, fluid intake, driven by the combination of thirst and the consumption of beverages at meals, allows maintenance of hydration status and total body water at normal levels.”[12] (p. 74)
“Water balance is regulated within ±0.2 percent of body weight over a 24-h period for healthy adults at rest (Adolph, 1943)… Newburg and colleagues (1930) demonstrated the accuracy of water balance studies to be within 0.5 percent of the water volume. Therefore, ad-libitum water balance studies can be used to estimate daily water requirements, provided the subjects have adequate time for rehydration and physiologic compensation.”[12] (p. 86)
“The AI for total water intake for young men and women (19 to 30 years) is 3.7 L (131 oz) and 2.7 L (95 oz)/day, respectively, which correspond to median intakes for this age group in the NHANES III survey… While it is recognized that the median intake for men and women 31 to 50 years was lower, there is no reason to assume that the level recommended for adults 19 to 30 years would be in excess. Therefore, the AI for those ages 31 to 50 years is set equal to that for younger adults…The AI for total water (drinking water, beverages, and foods) for the elderly is set based on median total water intake of young adults, rather than the older age group, in order to ensure that total water intake is not limited in the face of a potential declining ability to consume adequate amounts in response to thirst.”[12] (pp. 145–150)
2.2. Alignment
“Approximately 80 percent of total water intake comes from drinking beverages and water. While consumption of beverages containing caffeine and alcohol have been shown in some studies to have diuretic effects, available information indicates that this may be transient in nature and that such beverages contribute to total water intake. While the AI is given in terms of total water, there are multiple sources of such water, including moisture from foods, beverages such as juices and milk and drinking water. While all of these can contribute to meeting the adequate intake, no one source is essential for normal physiological function and health.”[12] (pp. 27–28)
“Figures 4–8 provides a compilation of 19 studies (181 subjects) where plasma osmolality was measured at several hydration levels…A strong negative relationship (p < 0.0001) (r = −0.76) was found between TBW changes and plasma osmolality changes… Clearly, plasma osmolality provides a good marker for dehydration status if water loss is greater than solute loss.”[12] (p. 93)
2.3. Coordination
“Tables 4–8 provides the serum osmolality for selected deciles of total water intake by gender in the Third National Health and Nutrition Examination Survey (NHANES III)… Serum osmolality concentrations were essentially identical (maximum range 3 mOsmol/kg) for the lowest (1st), middle (5th), and highest (10th) deciles within each age group. These data indicate that persons in the lowest and highest deciles of total water intake were not systematically dehydrated or hyperhydrated.”[12] (p. 114)
“The AI for total water intake for young men and women (19 to 30 years) is 3.7 L (131 oz) and 2.7 L (95 oz)/day, respectively, which correspond to median intakes for this age group in the NHANES III survey.”[12] (p. 145)
3. Potential for Alternative Methods for Gathering Evidence
3.1. Alternative Definition of Hydration
3.2. Alternative Assumptions
3.3. Alternative Water Intake Measure
3.4. Alternative Biomarker of Hydration
3.5. Alternative Population Reference Groups
4. Potential for Different Evidence If Alternative Methods Are Applied
4.1. Evidence of Need for Water
4.2. Evidence Regarding the Level of Water Intake Associated with Hydration and Health
5. Gaps in Evidence to Inform Drinking Water Recommendations for Chronic Disease Prevention
6. Opportunity for Strategic Planning
Author Contributions
Funding
Conflicts of Interest
References
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Past Methods for 2005 AI [12] | Alternative Methods for Future AI | ||
---|---|---|---|
Define | Standard of evidence | RCT | RCT |
Health | Acute | Acute and Chronic | |
Hydration | TBW | TBW and ECF/ICF | |
Working assumptions | Chronic TBW deficit does not occur, prospective assumption that healthy in youth precedes healthy in future midlife | Chronic osmotic stress occurs and affects health, retrospective assumption that healthy in midlife implies healthy in past young adulthood | |
Align with definitions | Units | Absolute | Relative |
Water intake measure | TWI in L | TWI and PWI in ml/kg | |
Hydration biomarker | In clinical studies, sensitive to TBW (serum osmolality) | In clinic, best practice for differential diagnosis, (serum sodium and urine osmolality) | |
Reference group | Ages 20–30 years, met hydration criteria and had no acute health condition | Ages 51–70 years, met hydration criteria and had no acute or chronic health condition | |
OBS data analysis | No risk factor control | Risk factor control | |
Coordinate | RCT data on hydration effects on health with population- representative OBS data on the level of water intake associated with hydration | Use biomarker to link | Use biomarker to link |
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Stookey, J.D.; Kavouras, S.A. Water Researchers Do Not Have a Strategic Plan for Gathering Evidence to Inform Water Intake Recommendations to Prevent Chronic Disease. Nutrients 2020, 12, 3359. https://doi.org/10.3390/nu12113359
Stookey JD, Kavouras SA. Water Researchers Do Not Have a Strategic Plan for Gathering Evidence to Inform Water Intake Recommendations to Prevent Chronic Disease. Nutrients. 2020; 12(11):3359. https://doi.org/10.3390/nu12113359
Chicago/Turabian StyleStookey, Jodi D., and Stavros A. Kavouras. 2020. "Water Researchers Do Not Have a Strategic Plan for Gathering Evidence to Inform Water Intake Recommendations to Prevent Chronic Disease" Nutrients 12, no. 11: 3359. https://doi.org/10.3390/nu12113359