If caffeine doesn't have an effect on someone (as in, they can drink a whole pot of coffee and then sleep an effortless 8 hours), then is excessive caffeine still bad for that person?

Whether or not you feel the increase in a marked fashion, you are more than likely not completely insensitive to it. It sounds like you’re not drinking coffee regularly – and that is the much more important factor in whether or not it is harmful. If you’re overexposed to it, that’s where it really will start to become a problem (unless, of course, your system is particularly sensitive to it – but this isn’t the case.)

You may have a genetic tolerance for it, but caffiene does affect you.

“Caffeine is metabolized in the liver by the cytochrome P450 oxidase enzyme system (to be specific, the 1A2 isozyme) into three metabolic dimethylxanthines,[63] each of which has its own effects on the body:

* Paraxanthine (84%): Has the effect of increasing lipolysis, leading to elevated glycerol and free fatty acid levels in the blood plasma.
* Theobromine (12%): Dilates blood vessels and increases urine volume. Theobromine is also the principal alkaloid in the cocoa bean, and therefore chocolate.
* Theophylline (4%): Relaxes smooth muscles of the bronchi, and is used to treat asthma. The therapeutic dose of theophylline, however, is many times greater than the levels attained from caffeine metabolism.

The precise amount of caffeine necessary to produce effects varies from person to person depending on body size and degree of tolerance to caffeine. It takes less than an hour for caffeine to begin affecting the body and a mild dose wears off in three to four hours.[30] Consumption of caffeine does not eliminate the need for sleep, it only temporarily reduces the sensation of being tired throughout the day.

In large amounts, and especially over extended periods of time, caffeine can lead to a condition known as caffeinism.[96][97] Caffeinism usually combines caffeine dependency with a wide range of unpleasant physical and mental conditions including nervousness, irritability, anxiety, tremulousness, muscle twitching (hyperreflexia), insomnia, headaches, respiratory alkalosis, and heart palpitations.[98][99] Furthermore, because caffeine increases the production of stomach acid, high usage over time can lead to peptic ulcers, erosive esophagitis, and gastroesophageal reflux disease.[100]”

Wikipedia

I’m not totally sure what exactly it is about caffeine that makes it “unhealthy”, since it’s been known to decrease the risk of Alzheimer’s and gallstones (by 45% in men!), and I know from living with my husband that it works wonders on asthma attacks.

I am one of “those people” that can drink coffee and go to sleep. In fact, nothing puts me to sleep quite like a mocha latte, whereas a Tryptophan pill like Alteril which knocks my hubby out cold hardcore is pretty much a guarantee for a sleepless night for me. I have no idea why this happens.

GQ Ive always wondered this. Like you caffeine doesnt do anything for me. Its quite unfortunate actually. I can down 2liters of soda and feel nothing. I wish I was able to be like ohh boy im feelin oftly tired lemme go grab an energy drink and be on my way. But to me energy drinks are just over priced soda. No boost of energy or anything :(

I am one of those people – caffiene has never had the effect of keeping me awake. I once went off it cold turkey because someone said they thought I was addicted. I didn’t touch a drop for a month and had no effects, then I went straight back on it the same as before (several mugs a day) and still no effect.

I am guessing that it’s just as dangerous for me as it is for anyone else to drink that much caffeine so I’ve since switched to decaff. I can’t tell the difference in any way (taste or affect) so I may as well go for the one that isn’t going to give me a heart attack or stomach ulcers.

Yes, because although you don’t physically feel the effects, and it may seem like there is no effect on you, it could still have effects on your body. Too much caffeine causes dehydration among other things.