Healthwise: Why you need 10 glasses of water a day


Mild dehydration, even when not linked to hangovers or illnesses, can precipitate moderate to intense headaches, including painful tension headaches and migraines.

With central and western India in the grips of a heat wave that has temperatures soaring well over 45 degrees Celcius in April, dehydration has become potentially as life-threatening as drug-resistant infections or driving blindfold on a highway.


Hot weather and the excessive sweating associated with it add to the fluids and electrolytes lost naturally as urine and saliva, which can cause dehydration very quickly during the summer months. Along with the water loss, sweating leads to an acute imbalance of electrolytes – such as calcium, sodium, potassium, chloride, magnesium and phosphate – in the blood, which are essential for the normal functioning of cells and organs, including regulation of heart and muscle contractions, maintenance of fluid balance and nerve functioning, stabilisation of blood pressure and heart rhythm, etc.


Dehydration can occur anywhere and anytime, with sun exposure, physical activity, fasting, extreme diets, certain medications, and illness and infections being major triggers. Among the common symptoms are tiredness, dizziness, headaches, dark yellow urine, dry mouth and irritability.


The absence of sufficient fluids in the body leads to a fall in the blood volume, which lowers blood and oxygen flow to the brain and other vital organs. The most common symptoms of an electrolyte disorder are irregular heartbeat, quickened heart rate, fatigue, nausea, vomiting, numbness and pain in joints, dizziness, especially when standing up suddenly, confusion and trouble concentrating.


Dehydration headaches


While stress, poor sleep, loud sounds and sinusitis are some established causes of headaches, a lesser known trigger is dehydration. Mild dehydration, even when not linked to hangovers or illnesses, can precipitate moderate to intense headaches, including painful tension headaches and migraines.


When the blood volume falls because of the shortage of fluids, the blood vessels dilate to increase blood flow to the organs and the brain, leading to pain. Electrolyte imbalance also makes the brain produce pain signals.


Dehydration-induced headaches can be prevented by having at least two to 2.5 litres of fluids a day, including water, milk, tea, coffee and juices. According to a study in the journal Neurology, migraine suffers who had four extra glasses of water a day on average had less severe and 21 fewer hours of pain on average than those who didn’t have additional water.



Diabetes and dehydration


People with diabetes risk developing dehydration very quickly because they have high levels of unutilised glucose in the blood, which makes the kidneys work harder to remove the excess sugar by excreting it as urine. Along with the excess glucose, they also lose water and electrolytes.


Lower blood volume also increases the glucose concentration in the blood and along with it, induces transient insulin resistance that makes cells unable to metabolise glucose, which further increases blood sugar levels. When cells cannot use glucose for energy, they burn fat and produce ketones, which increase urination and water and electrolyte loss.


Keeping newborns, toddlers and children who have blood volume because of their smaller size to begin with, hydrated is imperative, as it is for people over 65 years and those with multiple chronic infections and illnesses, such as heart disease.


Wonderful water


Dehydration can also occur indoors during the hot, dry summer months. Even people who don’t feel heat discomfort, say in an air-conditioned environment or even in a swimming pool, are at risk of getting dehydrated, so remind yourself to have glass of water every 30 minutes if you’re outdoors, and a glass every hour when indoors. An easy way to stay hydrated it having water just before stepping out and a glass as soon as you walk in from the heat.


Drinking water is all you need to prevent dehydration, but when fluid depletion in the body is severe enough to cause dizziness, vomiting and disorientation, lost fluids and electrolytes have to be replaced with an oral rehydration solution, which contains all the essential electrolytes in adequate amounts for rapid rehydration. The sachets of the formulation, which has the World Health Organization’s approval, are available at all public hospitals and private pharmacies, where it is priced between Rs 5 and Rs 30, depending on the brand.