The Caffeine Addict's Bible

Caffeine is actually addictive in the colloquial sense of the word – it stimulates the brain using the same mechanisms as amphetamines, heroin and cocaine. If you feel like you can’t get by without a daily coffee, that’s because you can’t – without it you’ll start to get withdrawal symptoms (more on this below). Similar to these drugs, the more your body gets used to caffeine the less effect it has, and you need stronger coffee to get that ‘buzz’.

Most of us get caffeine through food and drink, where it enters the blood stream through the gastro-intestinal tract. It then gets distributed around the whole body, including passing through the blood-brain barrier. It reaches maximum concentration in a about an hour (everything from weight, sex, age and liver health can affect this), and has a half-life of about 6-7 hours, which is why withdrawal symptoms generally take around 24 hours to manifest.

And what exactly is it doing in your body? Caffeine affects the central nervous system, the brain, cardiac muscle, respiratory system and the kidneys. It increases your metabolic rate by about 10 per cent, increasing the level of circulating fatty acids and in turn enhancing fat oxidation. In other words it can help to turn fat into energy faster, which is why some diet pills contain copious amounts of the stuff, although there’s no actual proof this is of any benefit when so many other factors are at play in dieting. Interestingly, women metabolise caffeine about 20 per cent faster than men and for both sexes the effect on the metabolism is reduced the more accustomed to caffeine the body becomes.

In the brain caffeine constricts the cerebral blood vessels. If you’re used to drinking several cups of coffee a day and then you quit cold turkey, the body can become oversensitive to adenosine. Since adenosine also helps regulate blood pressure, it can drop, resulting in an excess of blood to the head, causing a headache. Ergo, one of the best known withdrawal symptoms (Oh Gods, tell me about it –ed). While it doesn’t have an effect on sobering you up (see ‘Not the anti-drunk’ box), it’s this facet that does make coffee good for hangovers – constricting blood vessels may bring some relief from the hangover blues.

While the buzz and sense of altered-ness can be a nice pickup, there are a range of negative side effects too: insomnia is the most apparent problem given its effect on adenosine. Another side effect can be the ‘shakes’, the result of an over-stimulated nervous system and probably a good sign it’s time to cut back on your drug of choice.

When you do, classic withdrawal symptoms can appear – irritability, inability to concentrate, and restlessness are common. The best thing to do here is drink plenty of water and wait for your body to adjust back to normal.