It’s generally well-known that much of our body is made up of water, which plays a key role in maintaining multiple functions.

However, many people fail to drink enough water for countless reasons, from stress or to even a strong dislike towards its taste. Constant mild dehydration, day after day, means that our body does not function at its best and may be at risk for many problems and diseases.

Here’s why.


Effects of Dehydration

Sweat, excretion, vomiting, bleeding, breast feeding, all cause loss of water, which we replace throughout the day.

Mild dehydration – as little as 2% loss of water – can have a noticeable effect on the body. It causes dry mouth and eyes, headache, fatigue, loss of appetite, flushed skin, heat intolerance, light-headedness, burning sensation in the stomach, and dark urine with a strong odour.

During exercise, athletes can lose up to 6-10% of their water weight via sweat. This can increase fatigue and alter body temperature control, making exercise feel much more difficult, both physically and mentally. Exercise performance is optimal when athletes maintain fluid balance.

As dehydration becomes very severe (20%), blood pressure is very low, we feel drowsy, and kidney function is impaired. Other signs include difficulty swallowing, clumsiness, shriveled skin, sunken eyes and dim vision, painful urination, muscle spasms, and delirium.

Water plays a key role in the digestion, absorption, transportation, and use of nutrients (oxygen, minerals, vitamins, amino acids, glucose, and many more). So when there is less water, nutrients cannot reach where they are required.

Dehydration over long periods of time can therefore cause a constant state of malnutrition, leading to all sorts of nutritional and physical problems.

Here are a few examples:

  • Antioxidants from foods boost our immunity, while protecting our skin and hair from free-radical damage. When these antioxidants fail to get transported (something water, as we know, is largely responsible for), it can consequently affect the way we look and feel. Free-radical damage is also implicated in many lifestyle diseases like diabetes, heart diseases and cancer. This makes dehydration indirectly affect everything from ageing to diseases.
  • The lack of water in the body makes our blood thicken. This means that the heart has to work harder to circulate blood, which clots very easily, thus increasing the risk of heart disease.
  • Trypophan is an amino acid that’s required to make serotonin, a hormone that influences our mood. Dehydration may limit the amount of tryptophan available to the brain and cause mood disorders and depression. Many studies, ranging from children to the elderly, have shown that mild dehydration can impair mood, memory and brain performance.

Moreover, maintaining a good level of hydration has been shown to positively affect treating migranes, urinary tract infection, constipation, blood pressure, glaucoma, some complications of diabetes, and countless more conditions.


Hydration and Weight Management

Many people claim that drinking more water makes you lose weight by increasing metabolism and reducing appetite; these effects are mild and temporary. However, drinking half a litre of water about 30 minutes before meals seems to make people consume fewer calories.3, 4


Maintaining Body Fluid

A reduction in our total body water can happen because of two main reasons:[1]

  1. Water deficit (water loss dehydration)
  2. Salt and water deficit (salt loss dehydration)

How does salt fit into this equation?

Water in our body is found in two places: either inside the cells or outside the cells. The balance between these two, which is very important in order for the body to function properly, is maintained by salt. That’s why we’re given electrolytes (dissolved salts and glucose) in sports drinks, or when we are dehydrated. These additions allow water to be absorbed more quickly by the body.

Too much water can also be bad for you because the salts (and other nutrients) get diluted and cannot exert their effect or control the movement of water.


Some tips to maintain a good level of hydration:

During high heat and exercise, drink enough water from time to time, until you quench your thirst. Add some salt and glucose to your water if you feel very thirsty.

The health authorities commonly recommend about 2 litres of water in a day. But there are many factors that affect our individual needs. As a general rule, drink enough water for to have pale yellow colour urine. A bright yellow colour means you need more water. Some medications can also change the colour of urine. In that case, until you’re not thirsty anymore.

Thirst is generally a good sign of dehyration. However, older people may consciously need to watch their water intake, because our natural thirst mechanisms can start to malfunction in old age.

If you experience headaches on a daily basis, increase your water intake slowly to reach an amount that suits you.

Alcohol is a diuretic, i.e. it makes you lose water. Drinking a glass of water between alcoholic drinks can go a long way. It can also reduce the severity of a hangover.

Caffeinated drinks (tea and coffee) have a mild diuretic effect. The water loss is small enough to be replaced by water in fruits and vegetables. But moderation is still a good idea.

Speaking of fruits and vegetables, many of them have 80-90% water, along with fibre and other nutrients. These include cucumbers, salad greens, strawberries, watermelon etc. A diet rich in fruits and vegetables can help you stay hydrated.

If you do not like the taste of water, add a little bit of soda water or juice to it. Plain fruit juice will increase your fluid intake, but raise your calorie intake too, without the fibre benefits of eating whole fruits.

Only your body can tell you how much water you need! Just keeping an eye out for the signs of dehydration can help take a step closer to a healthier you.



1. Thomas DR, et al. Journal of the American Medical Directors Association 2008, 9(5): 292-301.
2.  Kleiner SM. Journal of the American Dietetic Association 1999, 99(2): 200-206.
3. Boschmann M, et al. J Clin Endocrinol Metab 2003, 88(12): 6015-6019.
4. Boschmann M, et al. The Journal of Clinical Endocrinology & Metabolism 2007, 92(8): 3334-3337.

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