Why Caffeine Tastes So Good
Chris - Our other guest this evening is Peter Rogers from the University of Bristol and Peter works on caffeine, amongst other things. It's my favourite drug for certain, so what's it doing to my body?
Peter - Well indeed it's the world's favourite drug, so it's easily the most widely consumed drug globally and therefore very important. So what's it doing to us? It has some pretty fundamental biological actions and has affects accordingly on many organs and tissues in our body, including the brain. It's affects are quite surprising and not what we think they are. For a start, the most obvious thing we think about caffeine is that we get stimulated by it. Certainly, we feel that stimulation when we wake up in the morning and have that first cup of tea or coffee.
Chris - It's pretty addictive isn't it?
Peter - Well I wouldn't use the word addiction with caffeine at all. I think addiction should be reserved for when there's compulsive use and so on.
Chris - I think my usage is pretty compulsive!
Peter - Well you probably consume it frequently but I think you could probably give it up quite easily.
Chris - Someone once put a jar of decaff in my cupboard and I didn't realise and went round with a headache for a week.
Peter - Yes, now that shows that you're physically dependent on caffeine, and I would say that caffeine causes dependence. You'd probably need about a week to get over the dependency, so it's quite easy to give up. The key thing is that in terms of your acute day-to-day functioning, you're probably functioning just as well without caffeine as you are with it once you've got over that initial withdrawal.
Chris - That perpetual headache, a feeling of lassitude and tiredness, an inability to concentrate, words gets tangled up in your head: it's got all the hallmarks of an addiction. When I drink this coffee here, when I take that into my body, what's actually happening?
Peter - What caffeine is doing is blocking adenosine receptors; cell surface receptors on cells in our brain and other organs in our body. Those cells' receptor are normally activated by adenosine that's produced by the body. Adenosine levels are actually increased during wakefulness and decreased during sleep. By blocking the effects of adenosine at those receptors, caffeine is keeping us stimulated and awake. An important issue is that with regular consumption of caffeine, that system adjusts itself. That system becomes more sensitive to the effects of endogenous adenosine, and we've shown in our experiments, that with regular consumption we're not actually getting a net benefit for our alertness and mood from consuming caffeine because of this readjustment of physiology.
Chris - So it has an effect for a little while and that wears off, so you're back to square one and you need the drug to feel normal.
Peter - You are. We've pretty much clearly shown that the buzz you feel in the morning is what we call 'withdraw-reverse'. So overnight you metabolise away the caffeine you consumed the previous day and you wake up feeling tired and lethargic, even after a good night's sleep. This is when you're in the early stages of caffeine withdrawal. Your caffeine in the morning picks you up and brings you back to normal, but not above normal.
Chris - Lots of these cold remedies you take when you have a cold are loaded with caffeine. The reason you feel so pepped up is that there's a microscopic dose of paracetamol, a whiff of aspirin and a massive slug of caffeine.
Peter - It's not got a massive slug. It's probably got a cup of coffee equivalent slug of caffeine in there, and that's obviously a misnomer, such as the idea of energy drinks having massive amounts of caffeine. You could get the equivalent amount of caffeine from an energy drink but much more cheaply. It's interesting that it's in analgesics and flu remedies. The benefit there is that you're reversing caffeine withdrawal again, because actually when you've got the flu, you don't feel much like drinking tea and coffee, so that's your replacement caffeine.
Chris - It's very good for people who want to sell you something. If you feel much better because all it's doing is pandering to your addiction, it's not really making you feel better at all, is it?
Peter - Well it's getting you back to normal. I would argue that you'd be better without consuming caffeine on a daily basis, although there are some longer term studies of caffeine that are very interesting.
Chris - That was going to lead me onto the next thing, which is: is this bad for us? We're all drinking this stuff, so if caffeine health deleterious?
Peter - I think it should be put in perspective and there are lots of other things that I would do first in terms of my behaviour to improve my longevity than giving up caffeine. All too often people say that of there's something wrong with you, you should give up caffeine. I think that's not the right approach to take because tea and coffee are actually part of our lives and they're enjoyable, so if there's no reason to give it up, don't give it up.
Chris - Is there any evidence that it is bad for you? They must have done some trial.
Peter - The greatest worry in terms of my understanding of the literature is concerned is that caffeine increases blood pressure, and we've already heard how that increases the risk of cardiovascular disease for example. But there's a lot of discussion about those effects. There are obviously these short-term caffeine effects such as caffeine withdrawal, which is not good for our everyday functioning. There are some interesting results suggesting that long-term caffeine consumption may be protective against cognitive decline later in life, and there's also evidence that it may be protective in relation to the risk of Parkinson's disease.
Chris - I think people have said, though, that smoking can protect you against Parkinson's and Alzheimer's, and cynics have said that it's because people who smoke don't live long enough to get those diseases. So maybe in caffeine's case, one could argue that there is a beneficial effect.
Peter - I think there is in relation to caffeine, and I don't think that that's a good explanation either, the smoking data or the caffeine data. There are good reasons to believe how caffeine may interact with Parkinson's disease because adenosine interacts with dopamine in the brain, and adenosine normally puts a break on dopamine function. So caffeine blocking that adenosine function may de-inhibit dopamine action, which is impaired in Parkinson's disease for example. So there are plausible mechanisms whereby caffeine could be protective with regards to the adenosine system and also in relation to Parkinson's disease.