Any deficit in normal body water – through dehydration, sickness, exercise or heat stress – can make us feel rotten. First we feel thirsty and fatigued, and may develop a mild headache. This eventually gives way to grumpiness, and mental and physical decline.
What happens in Dehydration ?
By the time you feel thirsty your body is already dehydrated; our thirst mechanism lags behind our actual level of hydration.
Research shows that as little as 1% dehydration negatively affects your mood, attention, memory and motor coordination. Data in humans is lacking and contradictory, but it appears that brain tissue fluid decreases with dehydration, thus reducing brain volume and temporarily affecting cell function.
As you “lose” body water without replacing it, your blood becomes more concentrated and, at a point, this triggers your kidneys to retain water. The result: you urinate less.
The thicker and more concentrated your blood becomes, the harder it is for your cardiovascular system to compensate by increasing heart rate to maintain blood pressure.
When your dehydrated body is “pushed” – such as when exercising or faced with heat stress – the risk of exhaustion or collapse increases. This can cause you to faint, for instance, when you stand up too quickly.
Here’s how to monitor your own hydration:
- Track your body weight and stay within 1% of your normal baseline. You can work out your baseline by averaging your weight (just out of bed, before breakfast) on three consecutive mornings.
- Monitor your urine. You should be urinating regularly (more than three to four times per day) and it should be a pale straw or light yellow colour without strong odour. If less frequent, darker colour or too pungent, then drink more fluids.
- Be conscious about drinking enough fluids. Your fluid consumption should prevent the perception of thirst.