Can I reset my tolerance for caffeine?

Ginny - Caffeine is used by so many people to keep them feeling awake. It's probably one of the most commonly used drugs, but it actually works by countering a substance in your brain known as adenosine. This builds up during the course of normal brain activity. There are receptors to monitor the amount of the substance and that's how your brain tells when it's coming to the end of the day, and you should maybe be getting a bit sleepy and thinking about going to bed.

Now caffeine is really clever because it looks quite similar to one of these adenosine molecules so that it actually fits into the receptors, but doesn't activate them.

So because the receptors are then blocked by the caffeine molecules, your brain is tricked into thinking there's less adenosine there and so, you don't get the feelings of sleepiness and that allows your brain's natural stimulants, the dopamine and glutamate molecules to work freely without being inhibited.

The strength of these effects can vary from person to person and it depends on loads of different factors, but partly, it's their level of tolerance. As with all drugs, continued use of caffeine does build up this tolerance. So, the first time you have a cup of coffee, you probably feel its effect very strongly, but if you've been drinking 5 cups a day for 10 years, you'll probably stop feeling the effects at all and actually, just need it to get back to a normal level. You can think of tolerance as the brain trying to get back to what it was like before you started drinking caffeine. So, if you push it in one direction, it's going to try and push back in the other direction. But that then means if you take away the caffeine, your brain is then too far the other way and this is where you get the withdrawal symptoms which can be quite extreme.

Chris - Headache.

Ginny - A lot of people get headaches, but you can also get nausea, you can get irritability, all sorts of horrible things. This tolerance can build up really quickly, actually between 1 and 2 weeks and can be really strong. So, even very high doses of caffeine can start not increasing your alertness after only 18 days or so.

Chris - There was a chemist in Glasgow University who did a study where he wants to know how much caffeine was in the coffees being served up at the average coffeehouse. If you go and buy a pack of cigarettes for example, they tell you how much nicotine there is in cigarettes. If you go and buy an alcoholic drink, it would tell you how much alcohol there is in it. You can go to any coffee chain and buy a coffee, but it doesn't tell you how much caffeine is in there.

This is important because there are risks to health for certain groups. Women who are pregnant - it's been shown - should probably try to keep their caffeine intake down below about 2 cups a day because any more than that can actually be associated with miscarriage.

And this gentleman found, by going into a number of - I think more than 20 - coffee shops in Glasgow, ordering an espresso and then immediately taking it outside, putting it in methanol and then freezing it in his lab to preserve the caffeine, he found that there was anything between 50 micrograms of caffeine which is the equivalent of a reasonable strength coffee up to 300 from one coffee shop! So that's the equivalent in just the same beverage of having 6 cups of coffee in one go from one store and just three in another. It's amazing, isn't it? It's incredible dosage!

Ginny - Wow, that's a huge difference.

Chris - So what should Ari do then? Should he ditch the coffee?

Ginny - Well sadly, the only way to get over this tolerance that I've found is to stop drinking the coffee. There are people who say it's better to go cold turkey and you may feel a bit rubbish for 10 days or so, but then it will get better. Other people say it's better to bring it down gradually. I think that's up to you, but the only real way to get over it seems to be, to stop it so that your brain can recover.