Caffeine facilitates learning in tasks in which information is presented passively
Caffeine facilitates performance in tasks involving working memory to a limited extent
caffeine appears to rather improve memory performance under suboptimal alertness conditions.
Most studies, however, found improvements in reaction time.
At low doses, caffeine improves hedonic tone and reduces anxiety,
The larger improvement of performance in fatigued subjects confirms that caffeine is a mild stimulant.
Caffeine has also been reported to prevent cognitive decline in healthy subjects (Nehlig N.p.)
If my husband doesn’t drink some by 10 a.m., he can expect a man-sized headache by early afternoon. My best friend can’t speak in full sentences until they get theirs. I’m talking about coffee, of course! But the real addiction here is to the caffeine IN coffee, not coffee itself.
The truth is that there are lots of ways to get your caffeine fix. Some of the people chugging down those Big Gulps all afternoon may be in it for the caffeine. Another popular way to get caffeine is tea, hot or iced. A can of diet cola (or similar) will give you around 42 milligrams of caffeine, while a cup of hot tea usually has almost 50 milligrams.
I’m afraid eating chocolate can’t compete with the caffeine power of a cup of Joe. Even a 2-ounce chocolate bar has only 36 milligrams of caffeine — a drop in the bucket for hard-core espresso drinkers! Not that caffeine is the main reason people eat chocolate, but be warned that getting your caffeine fix in the form of chocolate is going to cost you in calories! Two ounces of chocolate will run you approximately 270 calories and 16 grams of fat.
Here’s a chart of some common caffeine sources and exactly how much of a wallop each packs:
1 cup of regular coffee 138 mg caffeine
Espresso 1/4 cup 125 mg (Magee N.p.)
The effect of caffeine in stimulating self-reported alertness and mood was not thought to persist for extended periods of time, with the effects peaking during the first 4 hours after ingestion. Research in office workers suggests that consuming caffeine with ornithine (an amino acid involved in protein metabolism, found in foods such as dairy products and meat, and which can be synthesized in the body) in the morning had a positive effect on self-reported mood (especially reducing “feelings of fatigue”, and increasing “willingness to work”, and “vigor”) in the late afternoon, suggesting that ornithine potentiated the physiological action of caffeine59.