bs_bs_banner
Supplement Article
Challenges of linking chronic dehydration and fluid
consumption to health outcomes
Lawrence E Armstrong
The purpose of this article is to review the effects of chronic mild dehydration and
fluid consumption on specific health outcomes including obesity. The electronic
databases PubMed and Google Scholar were searched for relevant literature
published from the time of their inception to 2011, with results restricted to studies
performed on human subjects and reports in the English language. Key words
included the following: dehydration, hypohydration, water intake, fluid intake,
disease, and the names of specific disease states. Strength of evidence categories
were described for 1) medical conditions associated with chronic dehydration or low
daily water intake, and 2) randomized-controlled trials regarding the effects of
increased water consumption on caloric intake, weight gain, and satiety. This
process determined that urolithiasis is the only disorder that has been consistently
associated (i.e., 11 of 13 publications) with chronic low daily water intake. Regarding
obesity and type 2 diabetes, evidence suggests that increased water intake
may reduce caloric intake for some individuals. Recommendations for future
investigations include measuring total fluid intake (water + beverages + water in
solid food), conducting randomized-controlled experiments, identifying novel
hydration biomarkers, and delineating hydration categories.
© 2012 International Life Sciences Institute
INTRODUCTION
The inaugural ILSI North America Conference on Hydration and Health Promotion was convened in Washington,
D.C. during November 2006. This conference emphasized the importance of total water intake in the promotion of health and well-being. In part, because of the
recognition that little research had focused on the hydration needs of citizens with sedentary lifestyles and occupations,1,2 ILSI North America then organized the ILSI
North America Second International Conference on
Hydration & Health, which was held during November
2011 in Miami, Florida. One important aspect of these
conference proceedings was the hydration of average citizens with sedentary lifestyles and occupations, who experience mild dehydration of -1% to -2% of body mass.
Similarly, other conferences have emphasized the effects
of chronic mild dehydration on health, physiological
function, cognition, and performance. Published reports
of both scientists and clinicians3–7 serve to document that
few studies have evaluated mild dehydration. Today, this
matter continues to be of interest to scientists.8 Therefore,
the present article was prepared to 1) consider the effects
of chronic mild dehydration and fluid consumption on
specific health outcomes and diseases, and 2) describe the
greatest challenges to the design of experiments and the
interpretation of the relevant scientific literature.
Table 1 presents the available evidence for diseases
and medical conditions that may be associated with
chronic dehydration and underconsumption of
water.7,9–17 During development of this article, the
electronic databases PubMed and Google Scholar were
Affiliation: LE Armstrong is with the Departments of Kinesiology and Nutritional Sciences, University of Connecticut, Human Performance
Laboratory, Storrs, Connecticut, USA.
Correspondence: LE Armstrong, Departments of Kinesiology and Nutritional Sciences, University of Connecticut, Human Performance
Laboratory, Unit 1110, 2095 Hillside Road, Storrs, CT 06269-1110, USA. E-mail: [email protected]. Phone: +1-860-486-2647.
Fax: +1-860-486-1123.
Key words: disease, hydration assessment, obesity, type 2 diabetes, urolithiasis
doi:10.1111/j.1753-4887.2012.00539.x
Nutrition Reviews® Vol. 70(Suppl. 2):S121–S127
S121
Table 1 Evidence regarding diseases and medical conditions that may be associated with chronic, daily
dehydration or underconsumption of water.
Disease (no. of studies) Findings
Outcome variables
Referencesa
a
Colon cancer (n = 3)
Three studies (category III) reported Water intake (glasses/day);
Shannon et al. (1996)9;
a positive influence of fluid intake
total fluid (solid food +
Institute of Medicine
on reduced cancer risk.
water + beverages)
(2004)10
Insufficient number of studies
Bladder cancer (n = 8)
The relationship between fluid
Total fluid (solid food +
Institute of Medicine
intake and bladder cancer
water + beverages); only
(2004)10; Michaud
incidence has not been
beverages (mL/day); only
et al. (1999)11;
a
Radosavljevic et al.
substantiated (category III)
beverages (mL/day)
(2003)12
Total fluid (solid food +
Strippoli et al. (2011)13
Chronic kidney
Participants who consumed the
water + beverages)
disease (n = 1)
most fluid (3.18 L/day) had a
significantly lower risk of CKD
(odds ratio 0.5, P < 0.003) than
those who consumed the least
fluid (1.79 L/day) (category III).a
Insufficient number of studies
Urolithiasis (n = 13)
11 of 13 publications identified a
Evaluated renal function
Manz and Wentz (2003)7
significant association between
not fluid intake, review
favorable hydration status and
article
lower stone recurrence rate
(category IIb)a
Urinary tract infection
The influence of fluid volume on
Evaluated renal function
Manz and Wentz (2003)7;
(n = 8)
susceptibility to UTI is not
not fluid intake, review
Beetz (2003)14
substantiated by existing
article; methods not
literature (category III).a Several
stated, review paper
expert panels recommend a high
fluid intake for patients with UTI
(category IV)a
Chan et al. (2002)15
Fatal coronary heart
One case control study (n = 246 fatal Water intake (glasses/day)
disease (n = 1)
CHD events versus 8,280 males
and 12,017 female controls, aged
38–100 y) reported that increased
(>1.20 L/day) versus little water
(ⱕ0.48 L/day) intake had a
relative risk of 0.33, when
corrected for CHD risk factors plus
intake of other beverages
(category III)a. Insufficient number
of studies
Measured serum
Kelly et al. (2004)16
Venous
One study observed that patients
osmolality, not fluid
thromboembolism
with elevated serum osmolality
intake
(n = 1)
exhibited an increased risk of VT
(category III).a Insufficient number
of studies
Measured hydration
Kalhoff (2003)17
Exercise-induced
One study reported that mild
biomarkers, not fluid
bronchospasm
dehydration is a risk factor for EIB
intake
(n = 1)
(category IIb).a Insufficient
number of studies
Cerebral infarct, dental Insufficient number of studies and
Total fluid (solid
Institute of Medicine
diseases, gallstones,
relationship unsubstantiated
food + water + beverages);
(2004)10; Manz and
Wentz (2003)7
mitral valve prolapse,
evaluated renal function
glaucoma,
not fluid intake, review
osteoporosis
article
(<3 each)
a
Six categories of evidence: Ia, meta-analysis of randomized, controlled trials; Ib, at least one randomized, controlled trial; IIa, at least
one controlled trial without randomization; IIb, at least one other quasi-experimental study; III, descriptive studies such as comparative,
correlational and case-control studies; IV, expert committee reports, opinions, or clinical experience of respected authorities.
S122
Nutrition Reviews® Vol. 70(Suppl. 2):S121–S127
Table 2 Controlled, randomized trials investigating the effects of increased water consumption on factors related
to caloric intake, weight gain, and satiety.
Experimental approach
Findings
Referencesa
Consuming water with a Water (0, 237, or 474 mL) was consumed by men 30 min before
Rolls et al. (1990)18
meal
lunch, 60 min before lunch, or with lunch. Energy intake of this
meal was not altered by either water preload.
Consuming foods with a high water content more effectively
Rolls et al. (1999)19
reduced subsequent energy intake of lean women than did
drinking water with food.
Women were served breakfast, with or without 2 glasses of water.
Lappalainen et al.
The former decreased hunger and increased satiety during
(1993)20
breakfast. This effect did not extend beyond breakfast. Food
intake was not measured.
Laboratory-based meal study demonstrated that water consumed
DellaValle et al. (2005)21
with a meal reduced ratings of hunger and increased rating of
satiety.
Drinking water before
Both normal-weight and overweight/obese middle-aged and older Van Walleghen et al.
meals
adults ingested less energy during an ad libitum meal, when
(2007)22; Davy et al.
(2008)23
given a 500 mL water preload, 30 min prior to the meal (versus a
no-preload meal condition).
Young adults do not exhibit reduced energy intake following water Rolls et al. (1990)18; Van
preload. Coupled with the above findings, this suggests that
Walleghen et al.
age-related differences may exist.
(2007)22
Effect of water
In middle-aged and older adults, consumption of 500 mL of water
Dennis et al. (2010)24
consumption on
prior to hypocaloric meals led to greater 12-week weight loss
weight loss
than a hypocaloric diet alone.
Increasing daily intake
Increasing self-reported daily water consumption by ⱖ1 L in
Stookey et al. (2008)25
of water
overweight women was associated with increased weight loss of
~2 kg, during a 12-month dietary intervention, compared with
women who consumed <1 L water daily.
a
As controlled, randomized investigations, all studies in Table 2 exemplify the evidence category 1b (Table 1 footnote).
searched for the period from their inception to 2011, with
results limited to studies with human subjects and reports
in the English language. Key words used to perform the
literature searches included the following: dehydration,
hypohydration, water intake, fluid intake, disease, and the
names of specific disease states. Strength of evidence categories are described in the table’s footnote. As the table
shows, few studies have evaluated each of the diseases
listed, in part because investigations that explore the
effects of chronic low daily fluid intake (i.e., across
months and years) on disease progression are difficult to
design, conduct, maintain, and interpret. This lack of
evidence, coupled with a variety of outcome variables
(column 3), suggests that low daily water consumption
may someday be associated with specific diseases. To date,
however, urolithiasis is the only disorder that has been
consistently associated (i.e., 11 of 13 publications) with
chronic low daily water intake. With an eye toward
obesity and type 2 diabetes, Table 2 (discussed below)
summarizes the findings of eight intervention studies that
evaluated the influence of increased water consumption
on weight gain, caloric intake, and satiety.18–25
Nutrition Reviews® Vol. 70(Suppl. 2):S121–S127
CHALLENGES TO RESEARCH
The following four subsections describe obstacles to conducting effective research in this field. These subtopics
(i.e., evaluating drinking behavior; hydration indices;
accurate measurement of water intake; the etiology of
obesity) describe the difficulties that investigators experience when designing new studies and interpreting existing data. Until these challenges are overcome (i.e., within
the design of experiments), it is unlikely that our understanding of the effects of chronic underconsumption of
water on health outcomes will advance in meaningful
ways.
Evaluating drinking behavior across years
Considering the diseases and medical conditions
described in Table 1, it is obvious that some require days
or weeks to develop, whereas others require years or
decades (i.e., some forms of cancer). Controlled intervention trials spanning years or decades simply do not exist
and are difficult to design, for the following reasons:
S123
1) the number of subjects required for adequate statistical
power is large, and research is costly; 2) lengthy intervention studies suffer from participant noncompliance
and attrition, since it is difficult for any person to maintain a constant hydration state across years of his of her
life; 3) over 40 different types of cancer exist, with the
mechanisms and etiology of each type being subtly
unique, and the influences of water consumption possibly
different in each; 4) multiple personal characteristics,
dietary habits, or lifestyle behaviors may concurrently
encourage disease development, with their intercorrelation making interpretation of a single factor (e.g., daily
water intake) difficult; 5) without careful experimental
control of these factors, the probability of a type II statistical error increases (e.g., investigators declare there is no
effect, when one actually exists) – this is scientifically
important because studies that contain no significant
differences (i.e., negative findings) are more difficult to
publish.
Hydration indices: no gold standard exists
The physiological regulation of total body water volume
and fluid concentrations is complex and dynamic.26 For
example, the complex renal regulation of extracellular
volume involves not only arginine vasopressin and aldosterone, but also atrial natriuretic peptide and urodilatin.
Additionally, sweat gland, metabolic, and thirst responses
are involved to varying degrees, depending on one’s prevailing activities and dietary contents. The change of total
body water throughout any 24-h period is best represented by a sinusoidal wave that oscillates around an
average. Thus, all hydration indices (i.e., body mass
change, plasma osmolality, urine osmolality, urine specific gravity, urine color, 24-h urine volume, salivary
osmolality, rating of thirst, stable isotope dilution, bioelectrical impedance spectroscopy) are best viewed as
singular measures of a dynamic fluid matrix, containing
interconnected fluid compartments.
These facts have prompted several authorities to
conclude that no single hydration biomarker is accurate
and valid in all situations or all life activities.7,26–28 Recent
evidence also suggests that biomarkers may accurately
assess hydration changes acutely (within-day), but not
chronically (across days) (unpublished observations of E.
Perrier et al., 2011). Therein lies a major challenge to
linking under-consumption of water to health outcomes.
That is, the complex and dynamic nature of human fluidelectrolyte regulation makes it difficult to assess hydration state with great precision.26 And, if hydration state is
not precisely identified, the relationship between chronic
under-consumption of water and disease states cannot be
adequately assessed.
S124
Difficulties accurately measuring water intake
Measurements of water intake are essential to all hydration studies. Yet, even though the influence of water has
been studied for decades, 1) no scientific or clinical consensus exists regarding precise values for the daily water
requirements of men and women,10,29,30 and 2) surprisingly little data exist regarding the water turnover of
healthy, free-living, sedentary adults who are not under
environmental or physiological stress.31 Also, the published data describing human water requirements contain
recognized limitations that have been described previously.32 The foregoing facts indicate that accurate and
precise measurements of adult water consumption patterns are necessary but rare.
It is reasonable to ask why identifying chronic lowor underconsumption of water is a difficult task. One
answer lies in the methods and instruments that assess
human dietary intake, including water. Food diaries and
recalls are resource-intensive, time-consuming, burdensome for participants, provide only recent intake data
(i.e., not habitual intake patterns), and are not always
feasible in large-scale epidemiological studies.33 Further,
food diaries often do not describe 24-h human water
turnover accurately because 1) the water content of solid
food is not measured accurately,10,30 and 2) underreporting errors are common,34 no matter how carefully
researchers plan, control, and execute procedures. Indeed,
different methods of measuring dietary intake may
explain, in part, the differences between European Food
Safety Authority30 recommendations for daily adequate
intake of water (men, 2.5 L/day; women, 2.0 L/day) versus
those of the Institute of Medicine (men, 3.7 L/day;
women, 2.7 L/day).10 Other factors that may explain
these international differences in AI recommendations,
include: inclusion or exclusion of exercise and labor in
the consideration of human water needs,10,29 as well as
international and cultural differences in the selection of
food items (i.e., salty foods, large soup intake).7
Elusive etiology of obesity
Many countries have taken steps to plan for the rising
healthcare costs associated with an increasing incidence
of obesity and type 2 diabetes. For example, healthcare
costs for diabetes treatment in the United States exceeded
$116 billion in 2007, which was 11% of all health care
expenditures.35 Also, annual healthcare costs attributable
to obesity and overweight in the United States are projected to be $861 to $957 billion by the year 2030; this may
account for $1 of every $6 spent on health.36 Such trends,
now experienced in many countries, have focused government and research attention on causes. However,
many diseases have multifactorial origins.37 For example,
Nutrition Reviews® Vol. 70(Suppl. 2):S121–S127
the risk factors for obesity and type 2 diabetes are numerous (i.e., increased use of technology at home and at
work, reduced physical activity, increased caloric intake,
altered selection of food items, changes in the dietary
carbohydrate : fat ratio) and interrelated. It also is likely
that one causative factor predominates for some individuals, but not for others.
Water consumption may provide an approach to
counteracting this growing international healthcare
problem. Some researchers have hypothesized that
consumption of water, before or during meals, helps
overweight individuals manage their body weight by
increasing satiety or altering food intake.21,38 Table 2 summarizes the findings of eight intervention studies that
evaluated the influence of increased water consumption.
Energy intake, weight gain, sensation of hunger, and sensation of satiety were the primary outcome variables (evidence categories Ib, IIa, and IIb; see table footnote). The
findings of these eight studies indicate the following: 1)
they support a complex and dynamic network of behavioral and physiological factors that likely are influenced
by the timing of intake, volume of fluid consumed, mode
of fluid presentation (i.e., separated from or mixed with
solid food), and chronological age; 2) they suggest that
personal food and fluid preferences influence the relationship between water consumption and weight gain; 3)
water consumption may be effective for some individuals
but not others; and 4) they demonstrate that additional
research is required to interpret the subtle interactions
between water consumption, satiety, energy intake, and
weight gain.
Interestingly, water intake may increase energy
expenditure directly, independent of hunger and satiety.
One research team reported a 30% increase of resting
metabolic rate when obese men (n = 7) and women
(n = 7) consumed 500 mL of water39; this increase (i.e.,
approximately 100 kJ) peaked after 30–40 min. Similarly,
a 24% increase of metabolic rate was observed when a
different sample of obese men (n = 8) and women (n = 8)
consumed 500 mL of water40; however, no change of
metabolic rate was measured when these subjects consumed only 50 mL of water. Investigators concluded that
this inexpensive intervention might be useful to help
obese individuals attain increased energy expenditure.39
The work of Keller et al.5 suggests that high levels of
water intake may directly influence substrate utilization.
They examined the effects of hypo-osmotic cell swelling,
similar to a state of high fluid intake, by administering
desmopressin (a synthetic analogue of AVP) plus intake
of 2.4 L water in 12 h. The protein, glucose, and lipid
metabolism responses of 10 healthy young men were
observed. During the hypo-osmotic experiment, plasma
osmolality dropped from 286 to 265 mOsm/kg, and
resulted in protein sparing associated with increased
Nutrition Reviews® Vol. 70(Suppl. 2):S121–S127
whole body lipolysis, ketogenesis, and lipid oxidation;
insulin sensitivity of glucose metabolism was also
impaired. This acute metabolic state resembled fasting.
The authors concluded that a chronic, increased fluid
intake may reduce body fat stores.
The above studies demonstrate that science cannot
adequately explain the ways in which water consumption,
before or during meals, may help overweight individuals
manage their body weight.
EXPERIMENTAL APPROACHES FOR FUTURE
INVESTIGATIONS
Scientists today are discovering new ways that mild dehydration alters physiology and behavior. Contributing to
previous studies41–43 regarding the effects of moderate and
substantial dehydration (2.6–3.2% of body mass loss) on
cognitive performance, our research team published two
investigations that demonstrated cognitive impairment
and mood changes in women and men subsequent to
mild dehydration of only 1.39% and 1.59% of body mass,
respectively.44,45 Prior to these publications, none had
reported that dehydration of such a small magnitude,
without concurrent hyperthermia, would alter cognitive
function.
It appears there is also much to learn about chronic
dehydration and fluid underconsumption. The relative
lack of data in this field of study (Table 1), and the aforementioned challenges to the study of long-term health
outcomes, prompted the following recommendations.
These ideas are provided to encourage future research
regarding the effects of short-term and chronic dehydration on disease and health outcomes. They are organized
into two categories: fluid intake and hydration assessment. Future experiments (i.e., preferably controlled, randomized intervention trials) should investigate these
areas.
Fluid intake and disease. Such investigations would
include the following: 1) total fluid consumption from all
sources (solid foods + water + beverages)30; 2) consumption patterns for water, beverages, and water in solid food
that are consumed in various countries, providing data to
substantiate Adequate Intake recommendations for water
intake; 3) techniques, slogans, memory cues, and devices
that encourage humans to consume the daily AI of water,
as recommended by international health organizations10,30; 4) a brief, self-administered, valid, and reliable
beverage intake assessment tool to enhance measurements of water and beverage consumption33; 5) differences between high-volume drinkers and low-volume
drinkers – this group comparison technique offers
promise for observations of humans during ordinary
S125
daily activities (E. Perrier et al., unpublished observations,
2011); and 6) chronic underconsumption of water in
older adults, other than dehydration encephalopathy,
which has been associated with cognitive decline.46
Hydration assessment and disease. Such investigations
would include the following: 1) which hydration markers
are most useful to identify chronic mild dehydration; 2)
the definition of “optimal hydration,” which may be different for different physiological and cognitive functions
and for different body organs; 3) serum hormone concentrations (e.g., arginine vasopressin, aldosterone, cortisol)
as indicators of chronic underconsumption of water, or
as components of the mechanisms that underlie disease;
4) changes in international patterns of beverage consumption, and their relationship to obesity and type 2
diabetes; 5) numerous concurrent hydration indices,
within the context of an experimental intervention or a
group comparison (E. Perrier et al., unpublished observations, 2011), to identify novel hydration biomarkers that
are relevant to disease; 6) hydration categories (e.g., euhydration, extremely hyperhydrated, extremely dehydrated)
that are defined via statistical techniques, as useful guidance for the lay public47,48; 7) the dynamics of water turnover and water balance of obese individuals versus
individuals with a normal body mass index.
CONCLUSION
Considering the factors that influence weight gain, caloric
intake and satiety, it is widely appreciated (Table 2) that a
complex and dynamic network of behavioral, metabolic,
and physiological factors exists. This suggests that caloric
intake is influenced by the timing of intake, volume of
fluid consumed, mode of fluid presentation, chronological age, as well as personal food and fluid preferences.
Thus, because water consumption may be effective for
some individuals but not for others, this simple intervention deserves future research attention.
Finally, recommendations for future research focus
on the effects of dehydration and fluid consumption on
disease and health outcomes. These recommendations
are organized into two categories: fluid intake, and hydration assessment. Urolithiasis is the only disorder that consistently has been associated with chronic low daily water
intake. However, investigations that explore the effects of
chronic low daily fluid intake (i.e., across months and
years) on disease progression are difficult to design,
conduct, and interpret. Future investigations should
measure the effects of total fluid intake (i.e., including
water, beverages, and solid foods) on health outcomes,
especially obesity and type 2 diabetes.
S126
Acknowledgments
The concepts and opinions expressed by the author do
not represent those of the University of Connecticut.
Declaration of interest. The author is a consultant to ILSI
North America and to Danone Research. He serves on the
Danone Research Scientific Advisory Board and receives
funding to conduct research from Danone Research,
France.
REFERENCES
1. Arnaud M. Hydration Throughout Life. International Conference Vittel (France)
June 9–12, 1998. Vittel, France: John Libbey Eurotext; 1998.
2. Grandjean AC, Reimers KJ, Buyckx ME. Hydration: issues for the 21st century.
Nutr Rev. 2003;61:261–271.
3. Altieri A, La VC, Negri E. Fluid intake and risk of bladder and other cancers. Eur J
Clin Nutr. 2003;57(Suppl 2):S59–S68.
4. Maughan RJ. Impact of mild dehydration on wellness and on exercise performance. Eur J Clin Nutr. 2003;57(Suppl 2):S19–S23.
5. Keller U, Szinnai G, Bilz S, et al. Effects of changes in hydration on protein,
glucose and lipid metabolism in man: impact on health. Eur J Clin Nutr. 2003;
57(Suppl 2):S69–S74.
6. Wilson MM, Morley JE. Impaired cognitive function and mental performance in
mild dehydration. Eur J Clin Nutr. 2003;57(Suppl 2):S24–S29.
7. Manz F, Wentz A. 24-h hydration status: parameters, epidemiology and recommendations. Eur J Clin Nutr. 2003;57(Suppl 2):S10–S18.
8. Benton D. Dehydration influences mood and cognition: a plausible hypothesis?
Nutrients. 2011;3:555–573.
9. Shannon J, White E, Shattuck AL, et al. Relationship of food groups and water
intake to colon cancer risk. Cancer Epidemiol Biomarkers Prev. 1996;5:495–502.
10. Institute of Medicine. Dietary Reference Intakes: Water, Potassium, Sodium, Chloride, and Sulfate. Washington, DC: National Academy Press; 2004.
11. Michaud DS, Spiegelman D, Clinton SK, et al. Fluid intake and the risk of bladder
cancer in men. N Engl J Med. 1999;340:1390–1397.
12. Radosavljevic V, Jankovic S, Marinkovic J, et al. Fluid intake and bladder cancer. A
case control study. Neoplasma. 2003;50:234–238.
13. Strippoli GF, Craig JC, Rochtchina E, et al. Fluid and nutrient intake and risk of
chronic kidney disease. Nephrology (Carlton). 2011;16:326–334.
14. Beetz R. Mild dehydration: a risk factor of urinary tract infection? Eur J Clin Nutr.
2003;57(Suppl 2):S52–S58.
15. Chan J, Knutsen SF, Blix GG, et al. Water, other fluids, and fatal coronary heart
disease: the Adventist Health Study. Am J Epidemiol. 2002;155:827–833.
16. Kelly J, Hunt BJ, Lewis RR, et al. Dehydration and venous thromboembolism after
acute stroke. QJM. 2004;97:293–296.
17. Kalhoff H. Mild dehydration: a risk factor of broncho-pulmonary disorders? Eur J
Clin Nutr. 2003;57(Suppl 2):S81–S87.
18. Rolls BJ, Kim S, Fedoroff IC. Effects of drinks sweetened with sucrose or aspartame on hunger, thirst and food intake in men. Physiol Behav. 1990;48:19–26.
19. Rolls BJ, Bell EA, Thorwart ML. Water incorporated into a food but not served
with a food decreases energy intake in lean women. Am J Clin Nutr. 1999;70:
448–455.
20. Lappalainen R, Mennen L, van Weert L, et al. Drinking water with a meal: a simple
method of coping with feelings of hunger, satiety and desire to eat. Eur J Clin
Nutr. 1993;47:815–819.
21. DellaValle DM, Roe LS, Rolls BJ. Does the consumption of caloric and non-caloric
beverages with a meal affect energy intake? Appetite. 2005;44:187–193.
22. Van Walleghen EL, Orr JS, Gentile CL, et al. Pre-meal water consumption reduces
meal energy intake in older but not younger subjects. Obesity (Silver Spring).
2007;15:93–99.
23. Davy BM, Dennis EA, Dengo AL, et al. Water consumption reduces energy intake
at a breakfast meal in obese older adults. J Am Diet Assoc. 2008;108:1236–1239.
24. Dennis EA, Dengo AL, Comber DL, et al. Water consumption increases weight
loss during a hypocaloric diet intervention in middle-aged and older adults.
Obesity (Silver Spring). 2010;18:300–307.
25. Stookey JD, Constant F, Popkin BM, et al. Drinking water is associated with
weight loss in overweight dieting women independent of diet and activity.
Obesity (Silver Spring). 2008;16:2481–2488.
26. Armstrong LE. Assessing hydration status: the elusive gold standard. J Am Coll
Nutr. 2007;26(Suppl):S575–S584.
27. Shirreffs SM, Maughan RJ. Urine osmolality and conductivity as indices of hydration status in athletes in the heat. Med Sci Sports Exerc. 1998;30:1598–1602.
Nutrition Reviews® Vol. 70(Suppl. 2):S121–S127
28. Kavouras SA. Assessing hydration status. Curr Opin Clin Nutr Metab Care. 2002;5:
519–524.
29. Sawka MN, Cheuvront SN, Carter R 3rd. Human water needs. Nutr Rev. 2005;63
(Suppl):S30–S39.
30. European Food Safety Authority. Scientific opinion on dietary reference values
for water. EFSA J. 2010;8:1459–1469.
31. Grandjean AC, Reimers KJ, Bannick KE, et al. The effect of caffeinated, noncaffeinated, caloric and non-caloric beverages on hydration. J Am Coll Nutr.
2000;19:591–600.
32. Fulgoni VL 3rd. Limitations of data on fluid intake. J Am Coll Nutr. 2007;26
(Suppl):S588–S591.
33. Hedrick VE, Comber DL, Estabrooks PA, et al. The beverage intake questionnaire:
determining initial validity and reliability. J Am Diet Assoc. 2010;110:1227–1232.
34. Monsen E. Research: Successful Approaches, 2nd ed. Chicago, IL: American
Dietetic Association; 2003.
35. American Diabetes Association. Economic costs of diabetes in the U.S. in 2007.
Diabetes Care. 2008;31:596–615.
36. Wang Y, Beydoun MA, Liang L, et al. Will all Americans become overweight or
obese? Estimating the progression and cost of the US obesity epidemic. Obesity
(Silver Spring). 2008;16:2323–2330.
37. Manz F. Hydration and disease. J Am Coll Nutr. 2007;26(Suppl):S535–S541.
38. Negoianu D, Goldfarb S. Just add water. J Am Soc Nephrol. 2008;19:1041–1043.
39. Boschmann M, Steiniger J, Hille U, et al. Water-induced thermogenesis. J Clin
Endocrinol Metab. 2003;88:6015–6019.
Nutrition Reviews® Vol. 70(Suppl. 2):S121–S127
40. Boschmann M, Steiniger J, Franke G, et al. Water drinking induces thermogenesis
through osmosensitive mechanisms. J Clin Endocrinol Metab. 2007;92:3334–
3337.
41. Cian C, Koulmann N, Barraud PA, et al. Influence of variations in body hydration
on cognitive function: effect of hyperhydration, heat stress and exercise-induced
dehydration. J Psychophysiol. 2000;14:29–36.
42. Cian C, Barraud PA, Melin B, et al. Effects of fluid ingestion on cognitive function
after heat stress or exercise-induced dehydration. Int J Psychophysiol. 2001;42:
243–251.
43. Szinnai G, Schachinger H, Arnaud MJ, et al. Effect of water deprivation on
cognitive-motor performance in healthy men and women. Am J Physiol Regul
Integr Comp Physiol. 2005;289:R275–R280.
44. Armstrong LE, Ganio MS, Casa DJ, et al. Mild dehydration affects mood in healthy
young women. J Nutr. 2012;142:382–388.
45. Ganio MS, Armstrong LE, Casa DJ, et al. Mild dehydration impairs cognitive performance and mood of men. Br J Nutr. 2011;106:1535–1543.
46. Sakakibara R, Kishi M, Ogawa E, et al. Dehydration encephalopathy: a neurological emergency in the older adults. J Am Geriatr Soc. 2010;58:1819–1821.
47. Armstrong LE, Pumerantz AC, Fiala KA, et al. Human hydration indices: acute and
longitudinal reference values. Int J Sport Nutr Exerc Metab. 2010;20:145–153.
48. Cheuvront SN, Fraser CG, Kenefick RW, et al. Reference change values for monitoring dehydration. Clin Chem Lab Med. 2011;49:1033–1037.
S127