Hyponatremia, a word cobbled together from Latin and Greek roots, translates as "insufficient salt in the blood. Severe cases of hyponatremia can lead to water intoxication, an illness whose symptoms include headache, fatigue, nausea, vomiting, frequent urination and mental disorientation. In humans the kidneys control the amount of water, salts and other solutes leaving the body by sieving blood through their millions of twisted tubules.
When a person drinks too much water in a short period of time, the kidneys cannot flush it out fast enough and the blood becomes waterlogged. Drawn to regions where the concentration of salt and other dissolved substances is higher, excess water leaves the blood and ultimately enters the cells, which swell like balloons to accommodate it. Most cells have room to stretch because they are embedded in flexible tissues such as fat and muscle, but this is not the case for neurons.
Brain cells are tightly packaged inside a rigid boney cage, the skull, and they have to share this space with blood and cerebrospinal fluid, explains Wolfgang Liedtke, a clinical neuroscientist at Duke University Medical Center. Thus, brain edema, or swelling, can be disastrous. Where did people get the idea that guzzling enormous quantities of water is healthful?
A few years ago Heinz Valtin, a kidney specialist from Dartmouth Medical School, decided to determine if the common advice to drink eight, eight-ounce glasses of water per day could hold up to scientific scrutiny. After scouring the peer-reviewed literature, Valtin concluded that no scientific studies support the "eight x eight" dictum for healthy adults living in temperate climates and doing mild exercise.
In fact, drinking this much or more "could be harmful, both in precipitating potentially dangerous hyponatremia and exposure to pollutants, and also in making many people feel guilty for not drinking enough," he wrote in his review for the American Journal of Physiology—Regulatory, Integrative and Comparative Physiology.
People with certain kidney issues are also vulnerable since they can't properly process water and the problem isn't unique to water. For example, the same thing can happen if you down too much beer at once. That's called potomania. The good news is that there's an easy way to stay safe.
The average healthy adult needs somewhere around liters of water a day. And since this can come from food and other drinks too, drink when you're thirsty, and then stop. World globe An icon of the world globe, indicating different international options.
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How it Works. ORS Research. Founding Story. Our Mission. Mission Timeline. No items in your cart. Medical Conditions. Water is essential for life. The human body is made up of more than 60 percent water, and nearly 75 percent of the brain is comprised of H Drinking too much water or not having a way to remove it can cause water levels to build up. This dilutes important substances in your blood. Endurance athletes, such as those who run marathons and triathlons, sometimes drink too much water before and during an event.
The Institute of Medicine established guidelines for adequate water intake. So there is no exact formula on how much to drink. Common situations such as extreme heat, significant activity, and illness with fever will all require more fluid intake than average. In a healthy person, your urine is a good indicator of your hydration status. Pale yellow urine that looks like lemonade is a good goal. Darker urine means you need more water. Colorless urine means you are overhydrated.
In healthy people, athletes are at highest risk for overhydration. Sports experts at Harvard recommend that a logical approach to hydration while exercising is letting thirst be your guide. Some conditions and medicines cause overhydration by making your body hold on to more fluid.
These include:. Other conditions and drugs can cause increased water intake by making you extremely thirsty. Overhydration is more common among endurance athletes who drink large amounts of water before and during exercise. It has been reported among:. This condition is also more likely in people with kidney or liver disease. It can also affect people with heart failure. You may not recognize symptoms of overhydration in its early stages.
As the condition progresses, common symptoms include:. Untreated overhydration can lead to dangerously low levels of sodium in your blood. This can cause more severe symptoms, such as:.
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