The less you drink, the less you think! Effects of dehydration on Brain Health

Dehydration can seriously effect not only your body and the processes in your body, but also how your brain functions. Water accounts for 75% of the brain mass and during periods of dehydration, it will effect cognitive performance (Zhang, Zhang & Ma, 2018). Even slight dehydration can cause changes in problem solving ability, coordination and attention (Bahl, 2018). This only gets worse as you age. Older adults lose fat deposits in their body and therefore lose ability to store water. So they dehydrate more quickly. Many medications also cause dehydration. Very slight dehydration can cause confusion in the elderly. Make sure there are drinks available at all times.

How do you know you are dehydrated? It can be mild, moderate or severe. There are some symptoms to tell if you are dehydrated:

Mild to moderate: dark urine, less urine, dry mouth, dry skin, thirsty, lack of concentration, memory issues, attention issues, headache (one of the number one reason that people experience headaches is dehydration. (Try to drink a couple glasses of water with a headache without medication and if your headache decreases, it was dehydration!)

Severe: rapid heart rate, decreased blood pressure, sunken eyes, rapid breathing, muscle cramps, sleepiness, confusion, lack of problem solving abilities, irritability, lack of energy (This can lead to shock and electrolyte imbalances, so if you can't re-hydrate with an electrolyte containing fluid like pedialyte, you need to seek emergency care for IV fluids and electrolyte replacement)

According to Gunnars (2018), increasing water combats dehydration, and has other health benefits:

According to two studies, drinking 17 ounces (500 ml) of water can temporarily boost metabolism by 24–30%..

Researchers estimated that drinking 68 ounces (2 liters) in one day increased energy expenditure by about 96 calories per day.

Additionally, it may be beneficial to drink cold water because your body will need to expend more calories to heat the water to body temperature.

Drinking water about a half hour before meals can also reduce the number of calories you end up consuming, especially in older individuals.

So how much is enough? Truth is...8 glasses of water a day is a myth. It depends on who you are, where you live, your age, weight, diet and exercise level. If you are not experiencing mild to moderate symptoms listed above and you feel good, you are probably hydrated enough. Be careful of over-hydration though. Too much water can be just as attention to your symptoms.

Does it have to be water? No. Any fluids will do, but be careful of highly concentrated sugary drinks, too much caffeine and unnecessary calories in your drinks. Before considering dementia, consider dehydration!


Bahl, R. (July 26, 2018). Even 2 hours of dehydration can effect your body and brain. Healthline.

Gunnars, K. (June 2, 2018). How much water should you drink per day? Healthline.

Zhang, J., Zhang, N. & Ma, G. The effects of hydration status on cognitive performances among young adults in Hebei, China: A Randomized Controlled Trial (RCT). International Journal of Environmental Research and Public Health. July 15(7):1477.


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