PART I OF II
DRINK MORE WATER EACH DAY TO
Optimize Mood & Mental Tasks By Lawrence E. Armstrong, PhD
This article represents Part I of a two-part series. It explores the scientific studies that demonstrate the value of drinking water to optimize mood and cognitive processes. Part II, which will be published in the March/April 2017 issue of Bottled Water Reporter, will explore recent studies that link low daily water intake to a number of chronic diseases and will provide simple recommendations to help you maintain an optimal level of hydration. Most adults recognize that water is essential to health because it supports numerous physiological functions, including vision, circulation, metabolism, excretion of waste products, and regulation of body temperature. However, few people are aware of recent research that has discovered interesting and valuable cognitive benefits of consuming water each day.
water loss in these studies is approximately 1.0-1.5 percent of body weight, which is considered a mild level of dehydration. Studies comparing these dehydrated participants to a group of control subjects (who consumed as much water as they desired, and whenever they desired it, ad libitum) have revealed several interesting effects.
Scientists who study the effects of daily water intake on the human body asked test participants to stop drinking for half a day or longer, then observed the detrimental effects of the resulting dehydration. The amount of
Most adults rarely experience dehydration greater than 3 percent during their daily activities. The sensation of thirst and the finely-tuned actions of the kidneys maintain adult body weight within 1 lb (0.7%), from
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Mood & Mental Tasks
Most adults rarely experience dehydration greater than 3 percent during their daily activities. However, even mild dehydration—that is, 1-2%—can affect mood, energy level, and mental awareness. one day to the next. However, it is likely that most adults experience a 1-2% body weight deficit several times each week because thirst is not sensed until we reach a 1-2% body weight loss. Therefore, this article focuses on mild dehydration (1-2% loss of weight).
Controlled Laboratory Studies A Connecticut research team has published the findings of two mild dehydration studies (Ganio et al., 2011; Armstrong et al., 2012). The first involved a 12-hour body weight loss of 1.4% in young women and the second, 1.6% in young men. At those levels of mild dehydration, both groups experienced decreases on mental tasks, compared to control days when they were normally hydrated. Women reported headaches, increased task difficulty, and loss of concentration when mildly dehydrated; they also experienced mood changes in the form of reduced vigor and increased fatigue. Men similarly reported increased fatigue, plus greater anxiety. However, only men experienced poorer performance on computerized mental tasks, during vigilance and visual memory tasks. One year later, a French research group studied the effects of 24-hour fluid deprivation (FD) versus normal fluid intake, on selected mood and physiological factors (Pross et al., 2013). The
participating 20 healthy young women normally consumed 2.0–2.8 liters per day (L/d) of water. FD resulted in increased sleepiness and fatigue, lower levels of vigor and alertness, with increased confusion. These women also were more confused, less calm, and less happy. Interestingly, these mood changes were time-dependent, with greater impairments during the early afternoon (2:00 – 4:00 p.m.). This well-controlled investigation confirmed the findings of their initial study involving mild dehydration, which was published one year earlier (Pross, 2012). Modifying the amount of fluid consumed each day also can alter mood. Pross and colleagues (Pross et al., 2014) evaluated 52 women and men who habitually drank either a low volume (LOW = 1.5 L/d) or a high volume (HIGH = 2.7 L/d). During three controlled drinking days, the water intake of the 22 participants in the HIGH group was restricted to 1 L/day, whereas the water intake of the 30 LOW group participants was increased to 2.5 L/day. No purposeful dehydration was involved. In the HIGH group, the smaller volume of water resulted in statistically significant decreases of contentedness, calmness, positive emotions, and vigor. In the LOW group, drinking more water resulted in decreased fatigue, confusion/ bewilderment, and thirst, with a tendency toward less sleepiness.
A 2013 research investigation discovered the effects of drinking water on the reaction time required to perform a simple fine motor task: pushing a button. (Edmonds et al., 2013). Thirty-eight test participants abstained from drinking any fluid overnight; this resulted in a state of mild dehydration. In the morning, one-half were not given water to drink, and the other half consumed up to 1 L of bottled water, as dictated by thirst. The group that consumed no water had a slower reaction time than the group that drank water. The authors proposed that water consumption released mental resources (i.e., focused attention) that were otherwise occupied with brain processing of the sensations associated with dry mouth and thirst. Complex tasks also may be negatively influenced by dehydration, as shown in a 2015 study conducted in the United Kingdom (Watson et al., 2015). The aim of this study was to measure the effect of mild dehydration on performance during a prolonged, monotonous driving simulation task. This task consisted of a 2-hour continuous drive in an immobile car with a full-size, interactive, computergenerated road projection of a dull, monotonous four-lane dual highway. The computer screen “road” also had a hard shoulder and simulated auditory “rumble strips” (which were incorporated into white lane markings on either side of the highway and a barrier separating JAN/FEB 2017
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A U.K. study illustrated that mild dehydration affects the body similarly to sleep deprivation or a blood alcohol level of approximately 0.08%. the lanes), with long, straight sections followed by gradual bends. Drivers were instructed to remain within their lane unless overtaking slow moving vehicles. During the normal hydration experiment, volunteers were provided with 200 mL of fluid every hour, whereas only 25 mL was made available each hour during the fluid restriction experiment (FR); thus, test subjects lost 1.1 percent of their body weight during FR (mild dehydration). The magnitude of performance decrement during FR was similar to that observed following sleep deprivation, or the consumption of alcohol resulting in a blood alcohol content of approximately 0.08% (the current UK legal driving limit). A different experimental approach was taken by a group of investigators in the United States, who observed 120 healthy college-aged women during their normal daily activities (Munoz et al., 2015). These women drank water in volumes that ranged from less than 1.0 L/d to over 4.5 L/d, as shown in the figure at right.They were subsequently divided into three groups, to allow comparisons to be made: LOW volume (average, 1.5 L/d), MOD volume (2.3 L/d), and HIGH volume (3.1 L/d). Habitual total water intake (foods + fluids) during daily activities distinguished HIGH volume drinkers from the LOW and MOD groups. The entering, baseline mood scores of these women was assessed with the Profile of Mood States Questionnaire, which is widely accepted in psychological research and is sensitive to numerous stressors, including water 22
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restriction. Those who habitually consumed less water each day (see red line in the figure below) reported more tension, depression, confusion, and total mood disturbance (a summary score).
Practical Applications Since 2011, multiple randomized controlled research studies have identified the value of drinking adequate water to optimize mood, vigor, vigilance, visual memory, complex mental task performance, and fine motor reaction time; this included reducing the incidence of headache. However, it is important
to place in perspective the level of dehydration which these studies involved. All of the above experiments were conducted either in controlled laboratory settings or while healthy men and women went about their usual daily activities (i.e., no planned strenuous exercise sessions). When fluid was withheld, body weight loss in all studies reached 1-2%, a mild level of dehydration. Because humans do not perceive this level of mild dehydration until they become thirsty (i.e., at 1-2% body weight loss), it is likely that you reach this level of dehydration several times each week, without realizing it.
Daily Water Intake of 120 young women 20
Low Drinkers
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# of Women
Average Intake: 2.3 liters (2.4 quarts)
10
5
0 0.00
1.00
2.00
3.00
4.00
5.00
Water Consumed in All Fluids and Foods (L/24h)
Mood & Mental Tasks
If your goal is to optimize your mood, mental tasks, and processing of information, recent hydration studies provide sound evidence for optimizing your daily water intake. Therefore, if your goal is to optimize your mood, mental tasks, and processing of information, the aforementioned studies provide sound evidence for optimizing your daily water intake. To reach a minimum of 2.0 liters of total water each day (water + beverages + water in solid foods), remember that 22% of your total daily water intake is consumed as water in solid food; thus, you should drink at least 1.6 L of fluid, in the form of water and beverages. Indeed, the average volume of fluids consumed by Americans (plain water + moisture in beverages) is 2.7 L/d (men) and 2.2 L/d (women) (Yang & Chun, 2016).
The Harsh Side Effects of Mild Dehydration Recent research has shown that if you are mildly dehydrated—a 1-2% loss of body weight—there can be detrimental effects on your body, such as the following: • headaches • increased confusion/ bewilderment • mood changes • less calm/happy/contentment • decreased alertness • decreased positive emotions • reduced vigor • greater anxiety/tension • increased sleepiness and fatigue • increased task difficulty • loss of concentration
References • Armstrong LE, Ganio MS, Casa DJ, Lee EC, McDermott BP, Klau JF, Jimenez L, Le
Bellego L, Chevillotte E, Lieberman HR. 2012. Mild dehydration affects mood in healthy young women. The Journal of Nutrition. 142(2):382-8.
Lawrence E. Armstrong, PhD, is a professor of Environmental & Exercise Physiology at the University of Connecticut and the director of the Human Performance Laboratory. He presently serves as a trustee of the Drinking Water Research Foundation and as a scientific advisory board member for Danone Waters, France.
• Edmonds CJ, Crombie R, Gardner MR. “Subjective thirst moderates changes in speed
Part II of this series will be published in the March/April 2017 issue of Bottled Water Reporter and will describe how you can check your own hydration status each day, by making a few simple observations.
• Pross N, Demazieres A, Girard N, Barnouin R, Santoro F, Chevillotte E, Klein A, Le Bel-
of responding associated with water consumption.” Online journal. Frontiers in Human Neuroscience 16 July 2013, pg 1-8. Accessed at http://dx.doi.org/10.3389/ fnhum.2013.00363 on 23 Oct 2016.
• Ganio MS, Armstrong LE, Casa DJ, McDermott BP, Lee EC, Yamamoto LM, Marzano S,
Lopez RM, Jimenez L, Le Bellego L, Chevillotte E. 2011. Mild dehydration impairs cognitive performance and mood of men. British Journal of Nutrition 106(10):1535-43.
• Muñoz CX, Johnson EC, McKenzie AL, Guelinckx I, Graverholt G, Casa DJ, Maresh CM,
Armstrong LE. 2015. Habitual total water intake and dimensions of mood in healthy young women. Appetite 92:81-6.
• Pross N. 2012. Effect of a 24-hour fluid deprivation on mood and physiological hydration
markers in women. Nutrition Today 47(4):S35-7.
• Pross, N., Demazières, A., Girard, N., Barnouin, R., Metzger, D., Klein, A., Perrier, E. and
Guelinckx, I., 2014. Effects of changes in water intake on mood of high and low drinkers. PloS one, 9(4), p.e94754.
lego L. 2013. Influence of progressive fluid restriction on mood and physiological markers of dehydration in women. British Journal of Nutrition Jan 28;109(02):313-21.
• Yang, M. and Chun, O.K., 2015. Consumptions of plain water, moisture in foods and bever-
ages, and total water in relation to dietary micronutrient intakes and serum nutrient profiles among US adults. Public Health Nutrition 18(07): 1180-1186.
• Watson, P., Whale, A., Mears, S. A., Reyner, L. A., & Maughan, R. J. 2015. Mild hypohy-
dration increases the frequency of driver errors during a prolonged, monotonous driving task. Physiology & Behavior, 147, 313-318. JAN/FEB 2017
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