The authors have the following interests: This study was funded by Danone Research and conducted by Forenap. AD, NG, RB, DM, and NP were employees of Forenap, where the trial was conducted. AK, EP, and IG are employees of Danone Research. NP is an occasional consultant for Danone Research. There are no patents, products in development or marketed products to declare. This does not alter the authors′ adherence to all the PLOS ONE policies on sharing data and materials.
Conceived and designed the experiments: NP NG RB DM AK. Performed the experiments: NP NG RB DM. Analyzed the data: NP RB DM. Contributed reagents/materials/analysis tools: AK EP IG. Wrote the paper: NP AD EP IG.
To evaluate the effects of a change in water intake on mood and sensation in 22 habitual high-volume (HIGH; 2-4 L/d) and 30 low-volume (LOW; <1.2 L/d) drinkers who were asked to respectively decrease and increase their daily water intake.
During baseline HIGH consumed 2.5 L and LOW 1 L of water/day. During 3 controlled intervention days HIGH's water intake was restricted to 1 L/day whereas LOW's was increased to 2.5 L water/day. Several mood scales (Bond & Lader Visual Analog Scale (VAS), Profile of Mood States, Karolinska Sleepiness Scale, Thirst & Emotional VAS) were administered at different time points during the study. ANOVA including intervention, time point and intervention by time point as fixed effects on mean values (i.e.; baseline data
At baseline HIGH and LOW were comparable in mood state, except for thirst scores (estimate = 17.16, p<0.001) and POMS depression-dejection scores (estimate = 0.55, p<0.05) which were both higher in the HIGH
Increasing water intake has beneficial effects in LOW, especially sleep/wake feelings, whereas decreasing water intake has detrimental effects on HIGH's mood. These deleterious effects in HIGH were observed in some sleep/wake moods as well as calmness, satisfaction and positive emotions.
There is a growing body of literature showing that fluid deprivation negatively impacts several mood areas
Studies examining the effects of increased water consumption on mood and physiological sensations (e.g. thirst and headache) are even rarer. To the best of our knowledge, only three studies on this topic have been performed in healthy adults
The aim of the current study was to evaluate the effect of a change in water intake on several mood states and physiological sensations in high (HIGH; habitual fluid intake ≥2 L/d) and low (LOW; habitual fluid intake <1.2 L/d) drinkers who were asked to respectively decrease and increase their daily water intake. Based on the limited literature, it was hypothesized that in HIGH, a water decrease would negatively impact sleep/wake related moods. For LOW it was hypothesized that increased water intake would positively affect alertness and happiness ratings, as previously demonstrated in adults and young children.
This study was conducted at a single center in accordance with the ethical principles stated in the revised version of the Declaration of Helsinki and after approval on October 12th 2010 by an Independent Ethics Committee, Comité de Protection des Personnes Est IV, located in Strasbourg. The protocol was also approved by an institutional review board of the French Drug Agency, Agence Nationale de Sécurité du Médicament de Santé, on September 23rd 2010. All participants provided written informed consent.
After an eligibility check and before inclusion in the study, potential subjects were asked to report their habitual fluid intake at home in an electronic diary (Neometis-24WQ-Waters questionnaire) for three consecutive days. Among the 87 subjects enrolled, 35 were not included for the following reasons: habitual daily fluid consumption not consistent with inclusion criteria (N = 15), consent withdrawal (N = 9), other reasons (e.g.; positive urine test, poor venous system, N = 11). Eligible subjects whose total daily fluid consumption was consistent with the thresholds for low (LOW, <1.2 L/day, N = 30) or high fluid intake (HIGH, ≥2 L/day, N = 22) were included in the study. These cut-offs for fluid intake were based on previous research indicating that one third of the French population consumed less than 1.2 L of fluid per day and that one third consumed more than 2 L per day
The inpatient study period lasted 6 days (from the afternoon of Day 0 to the morning of Day 6) for both groups. All meals, sleep and waking hours were standardized. To minimize water lost to sweat, participants were permitted only sedentary activities such as reading, playing cards, or watching television. A drinking program was defined for each group (
Note: X corresponds to the mood and sensations assessments (i.e.; Thirst VAS, KSS, eVAS, POMS, Bond and Lader VAS).
Since circadian variations in mood have previously been reported
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All statistical analyses were performed with SAS version 9.1.3 (Cary, NC) with data from all subjects who completed the study. To compare LOW and HIGH groups at baseline, an ANOVA including group, time point and group by time point as fixed effects for each parameter was performed. Males were not included in the baseline comparisons since they were only represented in the LOW group.
To assess the effects of water intake switch in LOW and HIGH (i.e.; intervention effect) and to include circadian mood variations, an ANOVA including intervention, time point and intervention by time point as fixed effects on mean values (i.e.; Day 1 data
Results are presented as estimates (E), 95% confidence intervals (95% CI) and p-values (statistical level of significance at p<0.05, two-tailed). Means and standard deviations for the different mood scales are provided in the tables.
All 52 randomized subjects completed the study protocol and were included in the analyses. Based on fluid consumption at screening, 30 LOW and 22 HIGH were identified. Participant characteristics and habitual daily fluid intake volume, as reported during the screening period, are provided in
All | Low drinker | High drinker | ||
Number | n | 52 | 30 | 22 |
Mean ± SD | 24.8±3.1 | 24.9±2.9 | 24.5±0.7 | |
Min – Max | 20–30 | 20–30 | 20–30 | |
Male | 11 (21.2) | 11 (36.7) | - | |
Female | 41 (78.8) | 19 (63.3) | 22 (100.0) | |
Mean ± SD | 22.32±1.61 | 22.38±1.59 | 22.25±1.67 | |
Min – Max | 20–25.1 | 20–25.1 | 20–24.9 | |
Mean ± SD | 1.54±1.07 | 0.71±0.28 | 2.66±0.65 | |
Min – Max | 0.12–5.33 | 0.12–1.19 | 2.00–5.33 |
At baseline, HIGH and LOW were in comparable mood state, except for the thirst scores and the POMS depression-dejection scores. HIGH reported higher thirst feelings compared to LOW (group effect p<0.001, estimate = 17.16, 95% CI = [11.43; 22.88]) (
In HIGH, the Bond and Lader VAS scores revealed significant decreases in contentedness and calmness (p<0.05 and p<0.01, respectively;
Outcome parameters | Time point | p value (for main intervention effect) | ||||
07:00 | 14:00 | 16:00 | 18:00 | 20:00 | ||
Day 1 | −0.7±3.1 | −2.3±1.5 | −2.1±1.2 | −1.7±1.6 | −1.9±1.6 | ns |
Day 3-4-5 | −0.9±1.5 | −1.8±1.2 | −1.3±1.5 | −1.0±2.0 | −1.7±1.6 | |
Day 1 | 1.2±2.6 | 1.3±1.9 | 0.9±2.2 | 0.5±1.1 | 1.1±2.5 | ns |
Day 3-4-5 | 0.7±1.5 | 0.8±1.4 | 1.0±2.3 | 1.0±2.1 | 0.9±1.8 | |
Day 1 | 1.0±2.2 | 0.6±0.9 | 0.5±1.0 | 0.2±0.6 | 0.2±0.8 | ns |
Day 3-4-5 | 1.0±1.2 | 0.4±0.9 | 0.6±1.4 | 0.5±1.3 | 0.6±1.1 | |
Day 1 | 5.1±2.3 | 3.6±2.9 | 2.5±2.1 | 2.4±2.1 | 3.7±3.8 | p<0.05 |
Day 3-4-5 | 3.9±2.5 | 2.5±2.0 | 2.7±2.2 | 2.1±1.7 | 2.2±1.8 | |
Day 1 | −0.6±2.1 | −1.2±1.9 | −1.4±1.5 | −1.3±1.6 | −1.0±3.0 | ns |
Day 3-4-5 | −0.5±1.6 | −1.1±1.3 | −1.1±1.6 | −0.9±1.3 | −1.1±1.1 | |
Day 1 | 10.3±4.8 | 12.8±4.9 | 11.2±4.4 | 11.3±5.4 | 8.6±4.1 | p<0.001 |
Day 3-4-5 | 5.7 ±3.4 | 8.4±4.3 | 8.4±4.1 | 8.1±3.8 | 7.5±4.2 | |
Day 1 | 3.6±1.1 | 2.8±1.3 | 2.7±1.1 | 2.8±1.6 | 3.2±1.2 | ns |
Day 3-4-5 | 4.2±1.0 | 2.6±1.2 | 2.6±1.0 | 2.5±0.9 | 2.7±0.9 | |
Day 1 | 67.4±16.8 | 76.3±14.9 | 74.3±12.2 | 71.8±13.4 | 69.5±8.3 | p<0.05 |
Day 3-4-5 | 59.8±12.0 | 69.1±13.2 | 72.0±10.7 | 69.0±12.1 | 70.9±11.3 | |
Day 1 | 36.4±10.0 | 30.9±9.8 | 30.5±9.7 | 31.6±8.9 | 37.1±13.4 | ns |
Day 3-4-5 | 41.6±12.8 | 32.9±12.3 | 33.0±13.6 | 32.4±11.8 | 33.0±11.9 | |
Day 1 | 25.7±12.7 | 24.3±10.7 | 21.8±9.6 | 26.4±10.9 | 22.8±10.2 | p<0.01 |
Day 3-4-5 | 25.9±11.0 | 29.5±11.6 | 28.6±11.3 | 30.4±13.8 | 28.2±11.8 | |
Day 1 | 27.2±11.0 | 25.5±11.0 | 24.4±11.4 | 24.9±11.8 | 26.6±10.6 | p<0.05 |
Day 3-4-5 | 32.3±11.5 | 27.2±10.6 | 28.9±11.0 | 28.9±12.5 | 27.9±11.3 | |
Day 1 | 59.7±20.9 | 55.6±16.6 | 59.7±19.5 | 60.0±18.5 | 68.3±17.7 | p<0.001 |
Day 3-4-5 | 80.5±13.3 | 75.8±16.2 | 79.8±13.5 | 76.2±13.0 | 80.4±13.4 |
Abbreviations: POMS, Profile Of Mood States; KSS, Karolinska Sleepiness Scale; eVAS, emotional Visual Analogue Scale; B&L VAS, Bond & Lader Visual Analogue Scales; tVAS, thirst Visual Analogue Scale.
Significant time effects were present for fatigue-inertia (p<0.001), tension-anxiety (p<0.05) and vigor-activity (p<0.05) (POMS subscores), alertness (p<0.05) (Bond and Lader VAS subscore), sleepiness (p<0.001) (KSS) and emotional stability (p<0.01) (eVAS). The detailed time by time comparisons of all these variables (not shown) reported mood worsening at awakening (07:00) compared to the other time points.
No significant intervention by time interaction effects were present in HIGH.
Significant intervention effects were found for the POMS scores (
Outcome parameters | Time point | p value (for main intervention effect) | ||||
07:00 | 14:00 | 16:00 | 18:00 | 20:00 | ||
Day 1 | −0.3±4.1 | −1.9±1.9 | −2.3±1.6 | −1.6±1.8 | −1.8±1.5 | ns |
Day 3-4-5 | −1.3±1.4 | −1.8±1.6 | −1.7±1.6 | −1.7±1.7 | −1.8±1.7 | |
Day 1 | 1.2±1.7 | 0.8±1.4 | 0.5±1.0 | 0.2±0.6 | 0.5±1.2 | ns |
Day 3-4-5 | 0.5±0.9 | 0.6±1.0 | 0.5±1.1 | 0.5±1.1 | 0.7±1.7 | |
Day 1 | 1.8±2.8 | 1.1±1.5 | 0.5±0.8 | 0.4±0.6 | 0.5±1.0 | ns |
Day 3-4-5 | 0.9±1.6 | 0.6±1.1 | 0.4±0.9 | 0.7±1.4 | 0.6±1.1 | |
Day 1 | 5.0±3.7 | 3.0±2.4 | 2.1±2.9 | 1.8±2.3 | 2.7±3.2 | p<0.001 |
Day 3-4-5 | 2.3±2.3 | 1.8±1.8 | 1.9±1.9 | 1.7±1.7 | 1.8±1.8 | |
Day 1 | 0.8±4.0 | −0.8±2.1 | −1.0±2.2 | −1.0±2.1 | −0.5±2.0 | p = 0.05 |
Day 3-4-5 | −0.4±1.6 | −1.2±1.8 | −1.2±1.9 | −1.1±1.7 | −1.0±2.1 | |
Day 1 | 11.6±6.2 | 11.7±5.7 | 11.7±6.0 | 11.1±6.3 | 10.1±6.9 | p<0.05 |
Day 3-4-5 | 6.7±5.2 | 10.2±6.2 | 10.8±6.3 | 10.4±6.2 | 9.7±6.4 | |
Day 1 | 4.3±1.8 | 3.2±1.3 | 3.0±1.8 | 3.2±1.5 | 3.2±1.7 | p = 0.0729 |
Day 3-4-5 | 4.6±1.4 | 2.8±1.4 | 2.7±1.2 | 2.5±1.1 | 2.7±1.1 | |
Day 1 | 68.7±14.9 | 71.0±13.2 | 68.1±16.1 | 72.6±13.5 | 70.2±16.4 | ns |
Day 3-4-5 | 61.1±12.0 | 71.5±12.9 | 74.3±14.4 | 75.6±14.2 | 75.5±13.6 | |
Day 1 | 37.0±17.5 | 30.4±14.8 | 30.5±16.8 | 28.4±15.0 | 32.9±16.6 | ns |
Day 3-4-5 | 41.6±16.7 | 28.4±15.0 | 27.2±15.6 | 26.7±13.9 | 28.3±15.3 | |
Day 1 | 26.8±20.1 | 23.4±15.1 | 25.0±15.2 | 26.1±13.4 | 24.7±13.7 | ns |
Day 3-4-5 | 24.1±23.7 | 25.3±25.2 | 24.8±22.0 | 26.5±22.3 | 24.4±21.7 | |
Day 1 | 26.9±17.0 | 24.5±12.1 | 22.2±10.6 | 23.2±11.7 | 24.4±13.1 | ns |
Day 3-4-5 | 28.8±12.9 | 23.7±14.4 | 22.2±13.7 | 22.1±12.4 | 22.5±12.6 | |
Day 1 | 43.7±23.7 | 43.1±20.4 | 53.8±22.5 | 38.8±21.7 | 49.4±21.3 | p<0.001 |
Day 3-4-5 | 55.8±20.4 | 31.8±18.7 | 34.4±19.6 | 30.0±20.7 | 33.5±20.5 |
Abbreviations: POMS, Profile Of Mood States; KSS, Karolinska Sleepiness Scale; eVAS, emotional Visual Analogue Scale; B&L VAS, Bond & Lader Visual Analogue Scales; tVAS, thirst Visual Analogue Scale.
Significant time effects were found for several POMS scores (anger-hostility, p<0.01; confusion-bewilderment, p<0.01; fatigue-inertia, p<0.001 and tension-anxiety, p<0.05), for the KSS sleepiness score (p<0.001), the eVAS score (p<0.01), for the Bond and Lader alertness score (p<0.001) and for the thirst score (p<0.001). Detailed time analyses (time by time comparisons not shown) found worse mood at awakening (07:00) compared to the other time points.
Intervention by time interaction effects were all non-significant, except for the thirst scores. These analyses showed that the LOW indicated significantly higher thirst scores at awakening (07:00) after the water intake switch than at baseline (p<0.05). At 14:00, 16:00 and 20:00 thirst scores were lower after fluid increase than at baseline (p<0.05, p<0.001 and p<0.01 respectively).
This intervention study demonstrated that a daily water intake increase led to a significant mood improvement in habitual low drinkers, who reported less fatigue, less confusion, less thirst, and who tended to be less sleepy. Conversely, habitual high drinkers forced to reduce their daily water intake indicated that the restricted water intake negatively impacted their mood state; they indicated being more thirsty, less calm, less content, less vigorous, and reported lower positive emotions. Thus, the present research results suggest that an increase or decrease in habitual water intake have, respectively, an improving or worsening effect on mood and sensations depending upon an individual's habitual drinking habits (HIGH
According to the few published studies addressing water consumption and mood, the hypothesis was that a reduction in water intake in HIGH would have the same effect as fluid deprivation
One surprising finding was that HIGH were less fatigued during the intervention period of reduced water intake which is not only contradictory to the research hypothesis, but also to the observed decrease in the vigor. One explanation for this observation is that the lower fatigue scores were not directly related to the change in water intake habits but rather to the change in life habits required during the study. During the inpatient period all volunteers refrained from physical activity, performed limited intellectual activities without any form of stress and were required to sleep eight hours per night. Consequently it seems plausible that they felt less fatigued after several inpatient days compared to in everyday life where they are exposed to the stressors and rhythms of daily life (e.g. work).
The LOW who increased their daily water intake reported less fatigue and less confusion. The water intake increase also tended to decrease sleepiness. This positive effect on alertness of water intake has previously been described in other experimental conditions
Group comparison analyses showed that at baseline, mood in LOW and HIGH was similar except on subjective thirst feeling which was higher in HIGH than in LOW, and on the depression ratings which were also higher in HIGH. Both these group differences could be due to the fact that water intake was standardized (i.e.; given quantities at given time points) and was not an
Water intake standardization, defined as providing specified quantities of water at defined time points, may represent a bias in this study as indicated by the significant group differences in thirst and depression observed at baseline. In future research the effect of the structured drinking program should be taken into consideration when interpreting the results, at least on effects observed during the baseline period, as it seems to have an adverse effect on HIGH. It should also be noted that the drinking program during the intervention period was somewhat artificial because in real-life conditions, timing and quantities of drinking vary according to individuals and to the nature of fluids consumed
This study addresses the effects of a change in water intake on mood and physiological sensations in adults. The results showed that a switch toward an increase in water intake has especially beneficial effects on sleep/wake moods of habitual low-volume drinkers. The switch toward a decrease in water intake has detrimental effects on mood rating of habitual high-volume drinkers, including reduced feelings of calmness, satisfaction and positive emotions. Further research is necessary to confirm these results, using a less restrictive drinking program and a more appealing daily schedule of activities so that the effects of water intake changes can be more accurately assessed.