The other day, a very physically active friend was talking about health foods. After the usual dos and don’ts – five-a-day, protein and fibre in every meal, and so on – the subject of coffee came up. For me, coffee is a tasty beverage offering a quick pick-me-up, but apparently some people use it as a diet aid, hoping to burn more fat during metabolism. (NB my friend does NOT use coffee for this purpose.)
The substance of interest is caffeine: aside from its properties as a stimulant (the proper word is ergogenic – increasing the subject’s capability for mental and physical labour) , can also serve to boost your metabolism. The trouble therein is of course, to what extent? And with what side effects?
Fatty acids circulate in your body as tiny fuel cells. Caffeine increases the level of circulation. This in turn increases the rate of oxidation of these fuels, thus increases the overall oxidation of fat. This is useful news to runners, endurance athletes and people with similar hobbies. It is particularly effective in those who are not regular users.
For many of us coffee drinkers, we find that the effect wears off faster if we up the intake (say, around deadlines). We try to get around that by switching between different caffeinated drinks, or increasing consumption. What happens if you have too much? Is it possible to overdose?
The following extract is the abstract taken from research by K. Gilliland and D. Andress in American Journal of Psychiatry (1981; 138:512-514):
“Ad lib caffeine consumption, symptoms of caffeinism, and academic performance
The authors explored the relationship between ad lib caffeine consumption in college students and the incidence of caffeinism, characterized by heightened anxiety, depression, and various psychophysiological reactions. Students were randomly selected from four groups (abstainers from caffeine and low, moderate, and high consumers). A survey battery assessed the effects of caffeine, incidence of psychophysiological disorders, state-trait anxiety, and depression. The moderate and high consumer groups combined reported significantly higher trait anxiety and depression scores when compared with abstainers. The high consumer group also reported significantly higher levels of symptoms of caffeinism, higher frequency of psychophysiological disorders, and lower academic performance.”
Now we ask: how much is too much? 25 – 50 milligrams will have the pick-me-up effect in most people, offering alertness and lowering fatigue. Going to extremes, an acute overdose – caffeine intoxication – for the average adult is 300 milligrams, the result of which is colloquially known as “caffeine jitters”. See the image below for side effects.
A lethal dose for humans is approximated at 150 – 200 milligrams per kilogram of bodyweight. This would involve 80 – 100 cups of regular coffee, drunk within a certain time frame. So caffeine poisoning by drink may not occur too often, but is a larger danger for those who take caffeine pills.
However, it is not only products who literally wear their caffeine on their sleeve that contain the substance. Feast your eyes upon some other culprits:
Remember that moderation is always best.