The importance of water and brain function

water and brain function is important for brain longevity, the effects of dehydration of water on the brain is clear, image of a refreshing glass of water

The importance of water and brain function

Your human brain is composed of 60 % water. And hydration is crucial to the balance of nutritional elements within your brain cells. Water participates in metabolism and maintains electrolyte balance. As well as other functions. [1] Even mild dehydration (not drinking water for four to eight hours) can have an impact on mood. The effects of dehydration on the brain also include poor concentration, short term memory, and long term memory. [2] The effects of dehydration on the brain, over time can even result in permanent shrinkage of your brain’s grey matter. [3] Adequate water allows for the transport of essential nutrients. It also regulates the temperature of your brain. [3] Water and brain function can improve, simply by increasing blood flow and oxygen to your brain. [3]

Hunger vs thirst – what to do if you don’t crave water?

Firstly, you can assess if you are drinking enough water, by the colour and frequency of your urine. Your urine should be a pale straw colour. You can also tell if you are getting enough water by monitoring if you are hungry at inappropriate times (after dinner, or between meals). Or if you are craving sweets. Furthermore, if you are feeling disoriented or have a headache, or if you feel lethargic and fatigued, you may need more water. [3]

green smoothie with bonsai

It is reasonable to expect to drink about 6 – 8 glasses of water a day. However, this may be different for you, based on your sex, body weight, and levels of physical activity. The CSIRO dietitian Pennie Taylor suggests that you should drink 35 ml for every kg of body weight. [4] This equates to about 1 oz of fluid per 2.2 lbs of your body weight for our American cousins! However, keep in mind that some of this total will come through food.

Remembering to drink water

One problem is that it can be hard to remember to drink enough water each day. This is especially problematic if your thirst response is not active. Over time of consistent dehydration, your thirst response can start to be misunderstood as a hunger response. You may feel hunger at inappropriate times. And craving sweet foods like chocolate is another sign of dehydration.

asian cabbage salad mixed

The reason that hunger is actually a misunderstood thirst response maybe because the metabolism of food actually produces some water. And so, this is why eating food will provide some of your daily water needs. It is important to wait for 10 minutes after water is consumed, to see if you are still hungry. As that is how long it takes for the water to make its way into your body’s cells.

There are of course implications to drinking too much water. However, it is not all that likely that this will be an issue for you. As your kidneys can process about 0.8 to 1 litre of water an hour.

How to train your thirst response

So, how to train your thirst response to make you feel thirsty and therefore remind you to get up and get a glass of water? First, like vegetables, the more you drink water, the more you will want to drink water. Some techniques that I have found useful are setting an alarm every hour and when it goes off, getting a glass of water. It can also be helpful to place a pitcher or jug of water on your desk when you begin work for the day. This will prompt you to drink water during your working day. Perhaps you can put a note in your calendar to remind you until you get into the habit of this.

the effects of dehydration on the brain can be serious long term, water and brain function can be improved by remembering to drink more water

Another way to build the water habit into your life is by drinking a big glass of water the first thing you do (after brushing your teeth). I have done this every morning for years. And if you add a drop of Vitamin D to your water at this point, you might notice over time that your thirst response becomes more sensitive. This is likely due to increased calcium levels in your blood, due to the vitamin D supplement. [Please note that excessive thirst can be a symptom of vitamin D overdose.][5]

Is it better to drink filtered water for brain function?

You might be wondering if it is okay to drink tap water for brain function. Most of my research suggests that drinking tap water is fine. [6] It also cheap and convenient, which makes it all the more satisfactory. Some health writers suggest that the fluoride in tap water, in particular, can affect your brain in negative ways. [7] This is thought to be especially important for children and for pregnant mothers. [7] Of course, the levels of fluoride in tap water are very low. And have been endorsed by the National Health and Medical Research Council (NHMRC). [8] 

water and brain function - a running tap - is tap water okay?

My concern with the current Australian Drinking Water Guidelines report is that it makes a bold statement about the effectiveness of adding fluoride to water on dental health, without any cited research to back up these statements. [8] They also seem to gloss over the safety impacts of adding fluoride to drinking water. After reading the report, I was not satisfied with the level of evidence cited that the practice endorsed by the NHMRC in 1983, has been fully researched. [8]

However, this report was released by the NHMRC and although they do not cite evidence, they are a peak scientific body in Australia.

Water is naturally contaminated

In any case, water, from any source runs the risk of contaminants, by way of its passage through riverbeds, dams, and other earth-based structures. [8] Most medical authorities do support the drinking of tap water. [6] In places such as the USA, it can be less advisable, based on where in the country you are located and the source of your drinking water. [6]

However, even companies that have something to gain from promoting bottled water (which is also terrible for the environment), or filtered water, struggle to cite evidence for the improved health outcomes of people who drink filtered or spring water. 

Unless you are pregnant or have small children, there is solid support for the fact that tap water is fine for your health and your brain.

What are the effects of dehydration on the brain?

Not drinking enough water has an effect on short-term memory, long-term memory, and concentration. In one study, mild dehydration without hyperthermia in men induced adverse changes in vigilance and working memory, and increased tension/anxiety and fatigue. [9] Furthermore, being dehydrated by just 2% impairs performance in tasks that require attention, psychomotor, and immediate memory skills, as well as the assessment of the subjective state. [10] Another study, published in the American Journal of Clinical Nutrition found that drinking water improved focused attention and memory. [11] It is clear how important water is to brain function.

water and brain function, the effects of dehydration on brain function. concentrating painting her mum

As mentioned above, it has also been found that continued mild dehydration (not drinking for four to eight hours) can permanently shrink the grey matter in your brain. [3] For these reasons, you will enjoy many cognitive benefits and cognitive longevity from drinking enough water. 

What about alcohol, tea, and coffee?

If you drink a lot of coffee, alcohol, or even caffeinated tea, this will cause your body to lose more water, by wanting to urinate more regularly. [12] These drinks are diuretics and do not count towards your total water consumed during the day. If you drink a lot of these drinks, it might be worth considering cutting back. However, herbal teas, that are not caffeinated, as well as the water you get from eating fresh fruit and vegetables do contribute to your water count during the day.

almond milk cafe with cafe furniture and decor in the background

The takeaway – the relationship between water and brain function is clear

If you really want to take care of your brain, then one of the cornerstones of your diet should be to drink adequate water for your body weight and activity levels. The research on the relationship between water and brain function makes it clear that water improves cognitive performance, perhaps through increased blood flow and oxygenation. The effects of dehydration on the brain are numerous and can make you more aggravated or angry, less able to concentrate, and less able to use your working and short term memory.

The further benefits of drinking water are for overall health. Water helps to control your appetite, and reduce the incidence of headaches.

What have you noticed about the effects of dehydration on the brain? What tips can you give your fellow readers about getting into a habit with drinking enough water?


  1. Zhang, J, Zhang, N, Du, S, et al, 2018, ‘The Effects of Hydration Status on Cognitive Performances among Young Adults in Hebei, China: A Randomized Controlled Trial (RCT)’, Int J Environ Res Public Health, accessed at < >
  2. Hydration for Health, 2020, ‘Hydration, mood state and cognitive function’, Hydration for Health, viewed at < >
  3. Women’s Brain Health Initiative, 2018, ‘Staying hydrated boosts brain power’, Women’s Brain Health, viewed at < >
  4. Bullen, J 2017, ‘How much water do we need to drink a day?’, ABC News, viewed at < >
  5. Carter, A, 2018, ‘Can too much vitamin D hurt you?’, Medical News Today, viewed at <>
  6. Orsky, L, 2015, ‘Is it Safe to Drink Tap Water?’, One Medical, viewed at <’s%20true%20that%20the,convenient%20way%20to%20stay%20hydrated.
  7. >
  8. NHMRC, 2019, ‘Australian Drinking Water Guidelines’, NHMRC, viewed at <>
  9. Ganio, Matthew S., et al. “Mild dehydration impairs cognitive performance and mood of men.” British Journal of Nutrition 106.10 (2011): 1535-1543.
  10. Adan, Ana. “Cognitive performance and dehydration.” Journal of the American College of Nutrition 31.2 (2012): 71-78.
  11. Benton, D, Jenkins, KT, Watkins, HT, & Young, HA 2016, ‘Minor degree of hypohydration adversely influences cognition: a mediator analysis’, American Journal of Clinical Nutrition, vol. 104, no. 3, pp. 603-612.
  12. Johnson, A, 2016, ‘Boost your brain function with…water!’ That Sugar Movement, viewed at < >

Image credits

“concentrate” by Leonard J Matthews is licensed under CC BY-ND 2.0

“Jars Tourron Pitcher in jade used to serve water” by Didriks is licensed under CC BY 2.0

“Tap with running water” by leunix is licensed under CC BY-SA 2.0


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