The human body is made up of 70 percent water, says Dr Gaurav Jain, Consultant Internal Medicine, Dharamshila Narayana Super Speciality Hospital, Delhi. Drinking water is essential to maintain body temperature, detoxify the body through sweat, urine and bowel movements, and lubricate the joints.

“Many of us wake up feeling thirsty and instinctively reach for the water bottle on the bedside table to drink. But this can be a bad habit,” says Dr Gaurav Jain.

Dr Gaurav Jain explains that if water is left uncovered, it mixes with carbon dioxide. While there are no obvious harmful effects of this, it does slightly lower the pH of the water.

While drinking water left uncovered overnight is safe for a healthy person, drinking this water can be a risk for infection due to contamination as their immunity is low. Therefore, we need to drink and store water properly.

Sharing the same view, Dr. Ashit Bhagwati, an internist at Bhatia Hospital Mumbai (India), said that contamination can occur if water is not covered. This is because our environment is full of small dust particles and other pollutants that settle over time.

“Leaving a glass of water uncovered overnight will lead to contamination from dust and particles that exist in the air,” Dr. Bhagwati explained.

In addition, the water bottle can get foul after a period of use, making it necessary to clean the bottle after each use. Not cleaning the bottle also makes it a place for bacteria and other viruses to accumulate, which can enter the body through the bottle and the water inside.

Doctors also say that we should avoid drinking water kept in closed spaces such as cars. Because water kept for a long time in plastic bottles or closed spaces in cars is not safe because it heats up under sunlight and creates conditions for bacteria to grow.

The best way to consume water is to go to a water source such as a water purifier and get a clean glass of water, fill it up and drink it immediately.

Dr. Ashit Bhagwati further notes that storing water in plastic bottles should be avoided because the water can be contaminated with chemicals used to produce them.