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
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
# of Women
Average Intake: 2.3 liters (2.4 quarts)
Water Consumed in All Fluids and Foods (L/24h)