Can you drink coffee that has been left overnight

Do you usually drink leftover coffee the next day? Does this affect your health if you do it frequently?

Literally the overnight coffee doesn’t only refer to the coffee that has been left overnight, but left for several hours, even a couple of days. Almost all the coffee sellers would recommend you to drink fresh brewed coffee instead of storing it till the other day, generally speaking coffee won’t go bad too soon if you store it in the refrigerator, 3-4 days is Okay, while under room temperature you’d better dump it out after 12-24 hours. It’s safe to drink stale coffee, but the flavor is going to lose and the ingredients may be changed as well.

Does the amount of caffeine go lower in overnight coffee? It doesn’t seem to, caffeine is a very stable compound, it would not go changed during water evaporation. So it always stays there in your brewed coffee, even after all day or night. Don’t count on the caffeine degrade, while the other ingredients like antioxidants will degrade over time, which can protect against aging and many diseases that are partly caused by oxidative stress.

However, it is not guaranteed that the coffee with added milk will not go bad over a whole night, practically everyone knows that the drinking milk that sitting outside of a refrigerator for more than 2 hours probably goes bad, especially in summer. If you risk recycling it you’d better kill the bacteria by microwaving it.

There might be other factors which affect how long you can keep a cup of brewed coffee, the process how you brew it and the container you use may make a difference. When you use a good press coffee maker the ground coffee is filtered and it can last for days without deterioration. And you’d better store the rest coffee in a closed glass instead of an opened mug, of course, don’t forget to leave it in a refrigerator if you want to keep for more than 12 hours. 

If you drink leftover coffee frequently, it may not affect your health but the degraded antioxidant ingredients make the coffee less effective on anti-aging and anti-cancer, it somehow eliminates the healthy benefit of coffee. Plus, the taste and flavor is definitely worse than a fresh cup of brewed coffee, if you have time to brew coffee every morning it’s better not to drink overnight coffee.