9.6: Consequences of Deficiency or Excess

Hydration and Health

Like all nutrients, having too much or too little water has health consequences. Excessive water intake can dilute the levels of critical electrolytes in the blood. Water intoxication is rare; however, when it does happen, it can be deadly. On the other hand, having too little water in the body is common. In fact, diarrhea-induced dehydration is the number-one cause of early childhood death worldwide. In this section, we will discuss changes in hydration and electrolytes that compromise health.

High-Hydration Status: Water Intoxication/Hyponatremia

Water intoxication is extremely rare, primarily because healthy kidneys are capable of excreting up to one liter of excess water per hour. However, over-hydration can occur if urinary excretion does not compensate for water input. This was unfortunately demonstrated in 2007 by Jennifer Strange, who drank six liters of water in three hours without going to the bathroom while competing in a “Hold Your Wee for a Wii” radio contest. Afterward, she complained of a headache, vomited, and died. Water intoxication can also affect athletes who over-hydrate. Excessive water intake dilutes the concentration of sodium and other electrolytes.

Low-Hydration Status: Dehydration

Dehydration refers to water loss from the body without adequate replacement. It can result from either water loss or electrolyte imbalance, or, most commonly, both. Dehydration can be caused by prolonged physical activity without adequate water intake, heat exposure, excessive weight loss, vomiting, diarrhea, blood loss, infectious diseases, malnutrition, electrolyte imbalances, and very high glucose levels.

Physiologically, dehydration decreases blood volume. The water in cells moves into the blood to compensate for the low blood volume, and cells shrink. Signs and symptoms of dehydration include thirst, dizziness, fainting, headaches, lack of concentration, low blood pressure, fatigue, low (dark-colored urine) to no urine output, inability to regulate body temperature, weakness, and lethargy, and, in extreme cases, loss of consciousness and death. It is important to remember that the thirst mechanism is activated after dehydration occurs, so you are already dehydrated by the time you feel thirsty.¹ If a person is dehydrated for an extended period, the kidneys may not function properly. There is evidence that low-hydration status increases the risk of kidney stones and may be associated with chronic kidney disease.²

There are several risk factors for dehydration. Infants, athletes, and individuals with diabetes or alcoholism are more likely to experience dehydration. In addition, older people often suffer from chronic dehydration as their thirst mechanism is no longer as sensitive as it used to be.³

A person engaged in intense physical performance, especially in the heat or if heavy attire such as uniforms are involved, are at risk of dehydration if a good hydration plan is not in place. Examples of physical performance include military personnel, firefighters, or people who work in labor-intensive jobs. Research on athletic performance and dehydration supports the value of an athlete having a good hydration plan. Avoiding weight loss during an extended training session or event of no more than 2 to 3% of body weight may help the athlete avoid declining performance. Dehydration can impact both the physical and psychological aspects of sports performance. Tracking body weight change by weighing before and after an extended training session or event can serve as a good gauge of how well the athlete’s hydration plan is working. In addition to using weight as an indicator of hydration, athletes are encouraged to monitor their urine color, as shown in Section 9.3, and their thirst.⁴

Figure \(\PageIndex{1}\): Hydration and activity. Hydration status can be affected by physical activity, and without a good hydration plan, factors such as heavy uniforms and heat can lead to dehydration. "NLA, Lausanne HC vs. Rapperswil-Jona Lakers, 11th November 2014 03" by Fabien Perissinotto is licensed under CC BY-SA 4.0. https://commons.wikimedia.org/w/inde...curid=36740195

Heat Stroke

Dehydration can also contribute to abnormal temperature regulation in the body. Heat stroke is a life-threatening condition that occurs when the body temperature is greater than 105.1°F (40.6°C). It results from the body being unable to cool itself sufficiently by thermoregulatory mechanisms. Dehydration is a primary cause of heat stroke as there are not enough fluids in the body to maintain adequate sweat production, and cooling of the body is impaired. Signs and symptoms are dry skin (absence of sweating), dizziness, trouble breathing, rapid pulse, confusion, agitation, seizures, coma, and possibly death. Dehydration may be preceded by heat exhaustion, which is characterized by heavy sweating, rapid breathing, and fast pulse. The elderly, infants, and athletes are the most at risk for heat stroke.

Attributions

• Zimmerman, "An Introduction to Nutrition (Zimmerman)", CC BY-NC-SA 3.0. Text was updated and reorganized.

References

1. Dehydration. Cleveland Clinic. Updated June 5, 2023. Accessed October 13, 2023. https://my.clevelandclinic.org/healt...13-dehydration.
2. Roncal-Jimenez C, Lanaspa MA, Jensen T, Sanchez-Lozada LG, Johnson RJ. Mechanisms by which dehydration may lead to chronic kidney disease. Ann Nutr Metab. 2015;66(suppl 3):10-13. doi.org/10.1159/000381239.
3. Dehydration. NHS inform. Updated February 13, 2023. Accessed October 18, 2023. https://www.nhsinform.scot/illnesses...al/dehydration.
4. Belval LN, Hosokawa Y, Casa DJ, et al. Practical hydration solutions for sports. Nutrients. 2019;11(7):1550. doi.org/10.3390/nu11071550.