Nearly every function in the human body depends on the efficient flow of water through its system. Water transports hormones, chemical messengers and nutrients to our vital organs (the brain, heart, lungs, liver and kidneys). It helps us to digest and absorb vitamins and nutrients and flushes our liver and kidneys of waste.
When dehydration occurs, your body doesn't have enough water and other fluids to carry out its normal functions.
How Does Dehydration Impact Human Organs?
"Extreme dehydration affects all of the organs in the body. When you are very dehydrated — dehydrated to the point where you become light-headed or faint — blood flow to all of the organs is also lower than it should be," says Joshua Thurman, M.D. "The light-headedness (or loss of conscience) occurs because there is not enough blood flow to the brain."
Other organs can also be affected: If blood flow to the heart is too low you can feel chest pain, and if blood flow to the kidneys is too low you can feel abdominal pain.
"Severe dehydration is rare, but even mild dehydration can cause symptoms and affect your performance," says Dr. Thurman. "In addition to making you feel thirsty, dehydration can make you tired and lethargic, and cause headaches. You may feel lightheadedness when you go from sitting to standing. Usually this sensation clears up after a couple seconds, but it can be a warning to drink something or to use care when standing up until you can rehydrate."
Men and Women Dehydrate Differently
Approximately half of our body weight is water. The percentage is slightly higher for men than for women, on average. "Because less of their body weight is due to water, it takes less fluid loss for women to become dehydrated," says Dr. Thurman. "Women may sweat less than men, though, offering a bit of protection from dehydration. There are some studies suggesting that even mild dehydration can affect cognition and mood in both men and women."
ABOUT OUR EXPERT
Dr. Joshua Thurman, MD is a board-certified nephrologist and Professor of Medicine specializing in renal medical diseases and hypertension at the University of Colorado School of Medicine. He received his medical degree from the University of Chicago Pritzker School of Medicine and his undergraduate degree from Harvard University. He has been in practice for more than 22 years.