Water regulation in the human body is primarily controlled by the kidneys, with younger people having a broader range of urine concentration ability (40-1400 mOsm/kg) compared to elderly individuals (92-700 mOsm/kg). The body requires 2.5-3 liters of water daily under normal conditions, which can increase to 6 liters in extreme heat. Even mild dehydration (2-2.6% body weight) can impair cognitive function and physical performance. The article highlights that elderly and children are particularly vulnerable to dehydration - elderly due to reduced thirst sensitivity and kidney efficiency, while children due to their higher surface-area-to-body-mass ratio. An interesting finding from a German school study showed that providing water dispensers and education reduced diabetes risk by 31% in children. The article also debunks the myth that increased water intake significantly improves skin hydration and reduces wrinkles.
A study on endurance-trained cyclists revealed that dehydration significantly impairs cardiovascular function during exercise, especially when combined with hyperthermia. While hyperthermia or dehydration alone reduced stroke volume by 7–8%, the combination led to a 20% reduction in stroke volume and a 13% drop in cardiac output, causing greater cardiovascular strain. Restoring blood volume reversed the effects of dehydration alone, underscoring the critical role of hydration in maintaining cardiovascular stability during intense exercise in hot conditions.
A systematic review of studies found that producing less than 900 mL of urine per day increases the risk of kidney stones, with a minimum safe urine output of 1.6 liters per day for those who've had stones before. The most effective beverages for prevention include low-calcium water, citrus juices, and blackcurrant juice, while cranberry and plum juices have less favorable effects. Drinking an additional 1.3 liters of fluid daily can help achieve protective urine levels and reduce kidney stone risk.
The study highlights the significant impact of dehydration on sustained attention in middle-to-older-aged adults, who are more vulnerable to dehydration due to age-related changes in thirst perception. While dehydration did not impair memory or problem-solving, it made tasks requiring prolonged focus much harder. The findings emphasize the importance of staying hydrated to maintain mental sharpness, particularly for older adults.
Dehydration impairs concentration, short-term memory, and overall mood.
Dehydration is one of the factors that can influence the onset or exacerbation of headaches. Although the mechanism by which dehydration affects headaches is not fully understood, data suggest that this condition can impact the pain threshold, intensifying pain and increasing the risk of a range of disorders associated with headaches.