I heard that caffeine shortens your life (forgot by how much) because it forces your heart to basically go into overdrive and beat faster than it should. I also read that muscle shortens lifespan because you weigh more, and just like caffeine it needs to pump more blood faster. If this is true why? Wouldn't your heart adapt or something?

I wouldn't put too much stock into any of that. You could die next week from eating bad vegetables. I wouldnt worry too much, lol.

Worrying about these things also shortens your lifespan....

Caffeine is a problematic subject.
There are so many upsides and downsides it can get confusing.
In every way it is helpful it also causes damage and vice versa.

A few interesting up to date research results on caffeine:
* Caffeine consumption increases your BMR (High BMR means you burn more calories during the day) and helps weight loss {Study was made on obese women}
* Caffeine does NOT enhance metabolic activity during exercise and may even cause some damage if consumed in large quantities (5 mg of caffeine per kg of body weight). {This study was on fit yet ntrained men}
* Caffeine impairs Glucose Controlability in Type 2 Diabetic patients (Caffeine May Increase Insulin Resistance in Adults at Risk for Type 2 Diabetes)
* Caffeine can have certain protective effects on hear diseases {Study was made on heavy smokers}
* Drinking multiple cups of coffee each day may reduce the risk of gout in men

So is it good or bad for you? Depends on your situation and who you ask...
Noone can give you a definitive answer because noone really knows.

caffeine is great for you. end of story. take my life and liberty but leave me my coffee

Breathing slowly kills you too.

I try to limit my caf only because I'm not a big fan of bouncing off the walls.

Sadly most anything now days has a study where it can kill.

I remember seeing an article on where having sex can kill. Especially if the person your having sex with is married.

Some things kill you better than others. Anyway - with caffeine it is usually inconclusive anyway - even if you do listen to scientists...

I've found that sleep is pretty important for living well... If I had to choose between 6 hours of sleep and 3 cups of coffee or 8-9 hours of sleep, it's always the option with more sleep.

Sometimes I worry that I'm pre-diabetic or hypoglycemic, with exactly how much coffee affects me, because I can't believe that people consume so much if one cup makes them feel the same way as I do after one cup.

I have a high tolerance for caffeine. I usually get 500 or 600mg of caffeine daily and I get 7hrs of sleep plus an hour or 2 nap in the day. I usually down an energy drink and pass out in the day, "caffeine nap" it's supposed to make you more alert when you wake up. My only concern was when I heard that it leads to shorter lifespan, it was a while back but I wasn't concerned then as I am now so I just asked. I would assume the heart would just adapt around the intake, because our bodies adapt well to every other variable we throw at it.