Topical Area: Community and Public Health Nutrition, Obesity
Reviews consistently find that a loss of about 2% of body mass was needed before either athletic or psychological functioning is disrupted. However, although it is usually assumed that the minor changes in hydration status, that occur during normal life, do not impact on performance, experimentally the topic has been virtually ignored. The impact of everyday variations in hydration was therefore examined.
168 subjects were randomly allocated to drinking water, or not drinking, and in addition consume capsules containing either 300 mg of sodium chloride or a placebo. Subjects were monitored over a three-hour period, during which urine osmolality, loss of body mass and urine production were monitored. Repeatedly subjects reported their mood.
Subjects came having consumed their normal diet, without any restriction on fluid intake: on average 0.5% body mass was lost during the study. The major finding was that the hydration status on arrival had a greater influence, than subsequent fluid intake and changes in osmolality during the study. With ratings of being agreeable rather than hostile, those with lower baseline osmolality who drank water had better mood than if baseline osmolality was high. As another example, the mood of those who did not drink water only declined during the study when baseline osmolality was high rather than low. With measures of being composed rather than anxious, and being confidence rather than unsure, those who had lower baseline osmolality had a better mood, irrespective of whether water was consumed. Thus, baseline osmolality had an impact greater than drink induced changes in osmolality. Traditionally the normal range of urine osmolality has been said to be 200-800 mOsmoles/kg, yet the critical point at which the response to fluid intake changed was 600 mOsmoles/kg: 61% had a baseline osmolality over 600 and 38% over 800 mOsmoles/kg.
Some individuals are in a state of dehydration that adversely influences mood; a state not reversed by acute fluid consumption. The pattern of consumption associated with mild-dehydration and its functional consequences needs to be established.
Funding Sources : Funding Sources.There was no funding external other than provided by ** University