Here’s a good, though long, article on caffeine. Hightlights:
- Per capita caffeine consumption in the US increased almost 20% since 1995. Starbuck’s, anyone?
- Caffeine can cross the blood/brain barrier, unlike many drugs.
- In 30 to 45 minutes after ingestion, it is in every cell.
- Caffeine consumption is self limiting as at higher dosages one gets the shakes, etc. This is unlike other stimulant drugs such as cocaine.
- Women metabolize caffeine twice as fast as men.
- The most serious ill effects are sleeplessness and stress.
- … there’s more, you’ll have to read the linked article.
For me, caffeine is vitamin C.