How Harmful Is Overnight Water?

Uncovered water can absorb toxins. Johnson-Arbor believes dust, bacteria, and insects can contaminate open glass. "Includes everything floating or flying"

1. Contamination

Your body digests bugs or "anthropods" like any other meal, so this may not be as dangerous as it seems.

If you've ever chugged overnight-leftover water, you may have noticed a shift in taste. Johnson-Arbor explains.


"Carbon dioxide dissolves in a glass of water left out overnight," she says. "Carbon dioxide dissolves in water to form carbonic acid, making residual water bitter."

The NIH says your mouth has 700 bacteria species (NIH). Many bacteria!
Backwash occurs when liquids mingle with oral bacteria and return to the glass. This is why Johnson-Arbor believes you shouldn't drink from a glass of water left out overnight.

3. Bacteria are possible

"Our mouths contain microorganisms that infect water bottles and glasses," she says. While our own bacteria are unlikely to cause harm if we reuse a bottle or glass after leaving it out overnight, these germs could affect others and vice versa.

Overnight water changes taste but not safety. Bugs and dust may get in your glass, but they're harmless.

4. How Harmful Is Overnight Water?

"Water left out overnight may not taste as delicious, but it's unlikely to make someone sick," adds Johnson-Arbor. If there's no obvious contamination, it's safe to drink overnight-leftover water.

This one sauce causes weight gain and inflammation and should be avoided.

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