Do we really need 8 glasses of water a day?

Everybody is familiar with the recommendation that one should drink eight glasses of water per day. If you consider that two-thirds of the adult human body is made up of water, the need for this life-giving fluid is clear. But how much water should we really drink every day? There is no simple answer.

Why our bodies need water

Water is essential as every cell, tissue and organ in your body needs water to function optimally. This includes the brain, heart, lungs, muscles and skin, and even your bones.

Our body needs water to transport nutrients, regulate our body temperature, create bodily fluids like blood and saliva, lubricate the joints, cushion our organs, and eliminate waste though urine, bowel movements, breathing and sweating.

Being dehydrated means that there's an imbalance of water in the body, either because of more water being lost than normal or through higher water needs. Water can be lost when taking certain medications like diuretics; during illness when one has a fever; vomiting or diarrhoea; in hot or humid environments; or when exercising for long periods and/or at high intensities.

Water needs are also higher in pregnant and breastfeeding women, or if one suffers from conditions like constipation or kidney stones. Studies have shown that as little as 2% dehydration (equals a water loss of 1.6l in a person weighing 80kg) can affect the body. Other physiological functions affected include functions of the brain, gut, kidneys, heart (related to blood volume) and skin health. Dehydration can also cause headaches.

So, how much water should we drink? 

The age-old recommendation of eight glasses of water per day, while practical and easy to remember, is questioned by many healthcare professionals. It may be too simplistic to say that every person, regardless of weight, height, activity level or environment needs the same amount of water. The advice to drink to thirst is also criticised, as we can learn to override our thirst mechanism.

According to the Dietary Reference Intakes (DRIs) for Water, the average adult man needs 3.7l of water and the average adult female 2.7l daily, more if pregnant (3.0l), or breastfeeding (3.8l). Perhaps the best advice would be to drink water throughout the day, with higher volumes consumed when needs are higher.

A good rule of thumb is to use the colour of your urine to judge if you’re dehydrated, aiming for light-coloured urine and avoiding apple juice coloured urine.

How do we get additional fluids?

The National Board of Nutrition which published the DRIs recommends that 80% of our water needs should be met with plain water, and 20% can come from foods and beverages.

Examples of water-rich foods are fresh fruits and vegetables, which are good for our health in many ways. Although drinks like tea, coffee, juice and cooldrink also contribute to our total fluid intake, it is important to remember that plain water should make up the bulk of one's total fluid intake.

Smart hydration tip 

For some, plain water just doesn't taste good, while for others, getting into the habit of drinking water is the biggest challenge. Here are some practical tips to help you stay hydrated:

• Make it a rule always to drink a glass of water with every main meal, and preferably with snacks too.
  
• Always keep a visible source of water within arm’s reach, whether in a jug or a bottle. For example, make a habit of placing a jug of water on your desk as you get to work every day, and keep water bottles in gym bags, handbags and your car.
• Sparking water can be added to your daily water quota, as can herbal or Rooibos tea (without milk and sugar) and hot water, with or without a squeeze of lemon juice.
• Add flavour to plain, sparkling or bottled water with fresh fruit (e.g. diced apples, assorted berries, orange slices) or herbs (e.g. mint, basil, rosemary).
• Make healthy homemade iced teas by steeping four caffeine-free teabags like Rooibos in 1l of boiling water. When cooled down, remove the teabags and add one of the flavours mentioned above and serve as a drink, or pour into ice lolly moulds for a refreshing summer dessert.
• Freeze mint or lemon slices in ice trays to serve with water on hot days.
• Download a water reminder app on your smartphone to help you establish healthy water drinking habits.