5 ways dehydration can affect your health
Without water, humans can only survive a few days. Most of us would know how essential water is cell homeostasis and constitutes between 55 to 75% of our human body. You may have commonly heard that we need 8 glasses of water per day however, there is no single water requirement for a given person as individual water requirements can vary vastly based on different climates, different diets and different levels of physical activity. The water requirement for an individual is the minimum amount of water that equals water losses and prevention of dehydration.
Thirst and how it prevents dehydration
Thirst is our innate way of the body to maintain fluid levels. Factors that influence the trigger of thirst include blood pressure, blood volume, arginine vasopressin (AVP) which is the body’s primary water-regulating hormone and angiotensin II which causes our vessels to constrict. For older adults > 65 years of age, they may experience reduced thirst and water intake due to a reduced autonomic baroreceptor capability to detect a loss of blood volume. Hence they may be at a higher risk of dehydration.
Dehydration and thermoregulation
The human body’s temperature control relies largely on hydration status. In hot climates especially with physical activities that raise body temperature, sweating is the body’s way to cool down through evaporation of sweat. Water loss through the skin can range from 0.3 L/hr to 2 L/hr depending on heat and activity levels. If fluid replacement is not sufficient, this could lead to increase in core body temperature and reduction in plasma volume. Mild dehydration is also known to cause an imbalance in electrolyte levels and elevation in cortisol which is a stress hormone of the body.
2. Dehydration and Physical Performance
Reduction in physical performance levels in athletes has been observed with as little as 2% loss of body weight. The reduction in physical performance has been related to reduced endurance, increased fatigue, reduced motivation and increased perceived effort. This would be reduced stroke volume of the heart, reduction in blood pressure and reduced blood flow to the muscles. Sports that are higher intensity such as tennis, long distance cycling and running with longer duration are impacted more.
3. Dehydration and Cognitive Performance
Dehydration affects our cognitive performance as much as it affects our physical performance. Dehydration has been shown to affect concentration, alertness and short term memory. It can also affect perceptual discrimination, arithmetic ability, visual-motor tracking and psychomotor skills. Hence, your poorer mathematics ability may be a sign of dehydration.
In some studies, elevated mood scores which include fatigue, confusion, anger and vigour have also been shown.
4. Dehydration and Gastrointestinal function
There are many causes of constipation which includes poor diet, medication use, inadequate fiber intake and also inadequate fluid consumption. Constipation due to hypohydration can be easily managed by increasing fluid intake. In older adults, low fluid intake is a predictor for increased levels of acute constipation which can be easily addressed. During diarrhoea, maintaining hydration levels along with electrolyte levels can make the difference between life and death. In developing countries, it can result in 1.5 - 2.5 million deaths per year.
5. Dehydration and Headaches
Dehydration may be the cause of some headaches. In some observational studies, this is due to impaired concentration and increased irritability with dehydration that serves as a trigger for migraines. In those with dehydration-induced headaches, consuming water provided relief within 30 mins to 3 hrs for most individuals.
Check out the next blog on practical tips to maintain hydration.
References
Popkin BM, D'Anci KE, Rosenberg IH. Water, hydration, and health. Nutr Rev. 2010 Aug;68(8):439-58. doi: 10.1111/j.1753-4887.2010.00304.x.
Armstrong LE, Johnson EC. Water Intake, Water Balance, and the Elusive Daily Water Requirement. Nutrients. 2018 Dec 5;10(12):1928. doi: 10.3390/nu10121928. PMID: 30563134; PMCID: PMC6315424.
