Dehydration & Other Concerns of Water Intake in the Body

Dehydration & Other Concerns of Water Intake in the Body
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  • 0:01 Dehydration
  • 2:54 Causes of Dehydration
  • 3:26 Other Concerns
  • 5:00 Prevention
  • 5:48 Treatment
  • 6:22 Lesson Summary
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Lesson Transcript
Instructor: Jayne Yenko

Jayne has taught health/nutrition and education at the college level and has a master's degree in education.

Dehydration can be a serious, even fatal, condition. For the most part, we have control over how much fluid we consume and how much we exercise, which allows us to reduce and even eliminate most of the causes of dehydration. There are a few causes, however, that we have very little control over. Find out more in this lesson.


Today, you are going for your first hike in Death Valley. You have chosen the hottest day of the year, but between work and school, this is the most opportune time. You are in good physical shape and are looking forward to the quiet, unusual landscape of the desert. You have filled your backpack with trail mix, energy bars, and two liters of water. Have you brought enough water with you? Let's find out.

Dehydration is the excessive loss of fluids within the body, accompanied by osmotic imbalances. This occurs when fluid loss exceeds fluid intake, typically due to exercise or to a disease process. Most of us can handle a loss of three to four percent of body water. Five to eight percent will probably cause us to feel fatigued and dizzy. And over ten percent loss causes physical and mental deterioration, along with severe thirst. Death comes when the fluid loss is around 15%, as the body organs begin to fail, starting with the kidneys.

There are three types of dehydration: isotonic is an equal loss of water and electrolytes; hypertonic is primarily a loss of water; hypotonic is primarily a loss of electrolytes. Electrolytes are minerals that, in the human body, regulate fluid balance. The most common of these are sodium, potassium, calcium, magnesium, and chloride.

Hemorrhage, diarrhea, and vomiting all cause a direct decrease in blood volume. The body will increase sodium retention in the kidneys in order to maintain the potassium-sodium ratio, which increases blood volume. This can deplete the muscles of potassium, which leads to weakness. Severe potassium depletion affects the heart muscle, resulting in cardiac failure.

In mild dehydration, we will experience such symptoms as thirst, headache, dry skin, decreased urine output, confusion, and fatigue. If the dehydration lasts a long time or is severe, additional symptoms will appear, such as abnormally dark urine, rapid breathing, decreased blood pressure, delirium, seizures, unconsciousness, tongue swelling, and death.

There are many ways we lose body fluids. These ways are generally categorized as either sensible or insensible based on whether or not the loss is perceived by the senses. Sensible water loss would include sweating and vomiting; insensible would include respiration.

Causes of Dehydration

Some causes of dehydration in the human body include excessive sweating without consuming adequate water, particularly in a hot and/or dry environment; blood loss due to physical trauma; fluid loss due to severe burns or injuries; diarrhea; vomiting; infectious diseases such as cholera, gastroenteritis, and yellow fever; malnutrition from fasting or inability to swallow; diabetes; and Crohn's disease.

Other Concerns

Other influences on water balance in the body may include:

  • Female hormones, which increase sodium and water excretion, leading to an increase in potassium retention.
  • Diuretics are medications that reduce the fluid accumulation within tissue spaces caused by a number of disease conditions, such as congestive heart failure. These medications increase sodium and water loss, too.
  • Ethanol is the alcohol in alcoholic beverages that is a diuretic. It causes fluid to bypass the kidneys and go directly to the bladder. Hangover symptoms are signals to replace body fluids.

Drowning also causes drastic electrolyte imbalances, which vary depending on whether you are drowning in sea water or fresh water. The human body is approximately 0.9% salt. Sea water is 3.5% salt. When drowning in sea water, the accumulation of water in the lungs causes a rush of fluid from the blood to dilute the sodium concentration. Death is due to pulmonary edema, also called water in the lungs, and decreased fluid in the blood.

Drowning in fresh water causes the water in the lungs to spread into the blood to attempt to balance the potassium-sodium ratio. This influx of water into the red blood cells causes them to burst, also known as hemolysis, which releases large amounts of potassium into the body fluid, damaging the heart muscle, and then causing death by cardiac arrest.

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