How much is too much caffeine - and what does it do to the body? A Magazine feature published last week raised this question, and there was a huge response from readers.
Caffeine has been called the planet's most popular "psychoactive drug", and we asked for your stories of caffeine consumption. Here is a selection:
1. I drink a single cup of sweetened coffee a day. I brew it using a little Bialetti stove-top espresso maker. Somehow I'm missing something when I don't get to prepare my cup, even if I drink a cup from the drip coffee maker (which I prepare for my wife) or if I buy one at the coffee shop. It's as much about the process as it is about the beverage. Being a native of Belgium, I started early, about age 10. There have been times in my life when I drank more and when I drank none at all. I think there is a certain level of habituation involved, as is the case with most mood-altering foods and beverages. When I have a single cup (or any other caffeinated beverage) above my one-cup measure, I sleep poorly the following night. That one cup does it for me. Christian Franken, Saint Paul, Minnesota, US
2. I have been monitoring my tea consumption. Any tea drinking after 3pm will jeopardise my beauty sleep for the night. The tea can be of any type - English black tea, Chinese tea or the designer drink that has huge following in Asia - bubble tea that originates from Taiwan. It doesn't matter how much I drink - a cup or glass after the "curfew" time will trigger insomnia. Jessie Seow, Malaysia
3. In Costa Rica, even newborn babies are weaned on coffee when mothers dip their thumbs in coffee and allow the baby to suck on it. Of course, the afternoon coffee brings all business to a halt. Surely these parts of our culture cannot be bad... right? Max Ruiz, Santa Barbara, Costa Rica
4. Having been a smoker and knowing that first-cigarette-of-the-day feeling, I became alarmed when I recognised that same feeling for my first cup of tea. It was bliss, and quickly followed by another and another. By the end of the day, I would be drinking but without the enjoyment. A slave to the cup. I soon realised that I had an addiction and it needed to stop. So I did. I picked a week when I was on holiday and I quit. The next 48 hours were hell. Tiredness like you wouldn't believe along with flu-like symptoms. I folded. One cup of tea. Thirty minutes later and *boom* I was A-OK again. Since then I've weaned myself down to a lower level of use. After that experience, I suddenly understand why caffeine is in everything and posh coffee shops have sprung up in every orifice of the High Street. Dan K, Swindon, UK
5. On my 25th birthday party a long time ago, in the evening, I served espresso coffee in thermoses which the guests drank as though it was normal strength coffee. They reported finding it difficult to sleep when back home, just lying awake, staring into the ceiling. Hans Aberg, Stockholm, Sweden
6. I live in a city where it's normal to have home delivery of Coca Cola. Before I realised the damage I was doing to myself I used to consume 1.5l of diet cola every day, in addition to about four cups of tea and two or three coffees. One day I decided to go cold turkey and stop using the diet drink. The following day I was almost unable to function. It took me about three days to get to normal and I discovered I had lost more than 2kg (and I am a slim person). I put the weight-loss down to the aspartame in the diet drink, it appears to cause fluid retention. After a few weeks I drank a half-litre of diet cola during morning break, and became hyperactive and with a raging thirst. Since then I have stopped drinking all fizzy drinks and I only drink decaffeinated coffee. I feel a lot better for it. Clive Warner, Monterrey, Mexico
7. I have an autoimmune condition with symptoms of balance loss. Prescribed medication is completely ineffective in treating this. However six cups of strong black coffee spread through the day provides complete remission. M Birch, Thirsk, Yorkshire
8. Being from the home port of Starbucks, I am an enthusiastic consumer of caffeine, but only in the form of coffee and tea. No issues with it unless I go past about three big cups a day. In a recent visit to my doctor though, I had a chat with the nurse who told me about how many young blue-collar guys they see who have developed high blood pressure at 25 from living on energy drinks, which are full of sugar and caffeine. Plenty of young men and women seem to live on nothing else but these and beer. Here in the US, it's macho to drink the stuff, especially when you don't get enough sleep - all the overworked young professionals in suits with places to go and people to see. Gotta run, my triple caramel macchiato awaits... Lisa Dukes, Seattle, WA, US
9. I tend to drink about five diet soda cans worth of caffeine a day. If I exceed that, I start getting nervous, tense, and angry. If I drink coffee it upsets my bowels and makes me a raging grump. If I don't get my caffeine, I feel a little down, obsess over getting my next soda, and suffer headaches. I am definitely addicted to caffeine. Bonnie J Lincoln, McAlester, Oklahoma, US
10. In a typical day I consume eight to 10 cups of coffee. Nothing compares to the wonderfully bitter, rich taste and aroma, and good quality stuff is freely available at my workplace. I find that the quantity of coffee consumed doesn't really affect me, but the strength does - one espresso might cause shakes where two litres of filter coffee wouldn't. M Greenhalgh, Slough, UK
11. As a writer and painter, I consume as much coffee, tea and energy drinks as possible. One particularly epic coffee session at Sweet Mother's Kitchen in Wellington, Aotearoa, led to the discovery of an entirely new abstract-tribal bird of paradise which has been successfully depicted on the walls of a hotel in Patong Beach, and a rune-illuminated example that currently hangs in a bar in Krabi. Sweet Mother's do a mean bottomless cup of coffee which is satisfyingly strong, copious and lights up the neurons like city lights after dark. I heard during a psychology lecture back in the 1990s that extroverts are often low in a certain brain chemical known as norepinephrine, meaning they need the added stimulation of music during work or exciting jobs such as fire-fighter in order to prevent the neurons from falling asleep. Coffee might accomplish a similar task. Rob Fewster, Krabi, Thailand (originally Rainham, Kent)
12. What the article says is true: each person's metabolism is different. I started drinking caffeine at the age of five, when my grandma in Peru used to make the cafe con leche (coffee and milk) for us. Now I'm an adult and I know my own limits - one cup of coffee with cream and sugar in the mornings, another (optional) cup in the afternoon. Taking coffee in the evening or at night will give me insomnia. Jorge Collantes, Toronto, Canada
13. I have never exceeded "my limit". I do admit I need a cup of coffee to start my day (my car needs petrol) and during the day, it's a pleasant habit to go and make some coffee. Whether it enhances my creativity, I am not sure. I do, however, enjoy painting more with a cup of coffee on the table beside me. Jo-Anne Nelson, Durban, South Africa
14. I probably (definitely?) exceed my limit each day. I'm sitting here at 1:30am because I can't sleep. I'm caught in vicious cycle. I spend a lot of time at the gym. I need energy for the the gym so I take pre-workout supplements (with shed-loads of caffeine) because they work well and I get good results from them. Also, I'm an English teacher, I need a lot of energy for my job. When I'm at work, I drink oolong tea (as much as I need to to keep me going). As a result of all this I've recently begun to suffer from insomnia. So, after three or four hours sleep, I need more caffeine to keep me functioning efficiently. It's not a major problem, just an inconvenience, but my only concern is my blood pressure, which has always been normal and healthy. As soon as I develop high blood pressure as a result of my caffeine intake, then it will definitely be time to cut down. Phil Wills, Xiangyang, Hubei, China
15. As a Colombian, I wish there was some restraint in the way people take caffeine. A good coffee to start the day is about much more than caffeine intake, so I would not like that custom to suffer from the fear caused by those that abuse it and end up badly. My resistance to caffeine is very high, I have not noticed any stimulation from it, and I could go to sleep right after a brew as strong as they make (or the ones I make that are even stronger). By the same token, I have never experienced any withdrawal symptoms. So, I hope as many people as possible enjoy coffee like me, for its taste and the ritual, with no caffeine added to other foods and drinks. Juan Villarreal, Bogota, Colombia
16. I am pregnant, so I try to consume as little caffeine a day as possible. But at the moment I have quite a lot of work to do, so I do have my latte macchiato on my way to work. I don't think it will do much harm to the baby, if at all, because in general they tell you under 200mg a day is fine in pregnancy. I think, there should be more information available on how much caffeine is in all those drinks, especially the many "to go" coffees that so many like me get on their way to work. I wrote an email to the cafe chain where I get my coffee to find out, but they haven't replied yet. I still drink their coffee though... Ida, Greifswald, Germany
17. After careful self-experimentation, I've found out if I drink more than two cups of coffee or tea, my heart starts racing, I get muggy-headed, and I run the risk of starting a heart arrhythmia. The arrhythmia could last a few weeks, until my heart reverts back to a steady beat. I'm very careful with how much I drink now. Adam M, Sheffield, UK
18. I drink between four and seven cups of strong coffee a day. I am also in the process of finishing an MA in TV scriptwriting and find that I cannot get down to write a script unless I've had my caffeine fix. The ritual of brewing the coffee (or, in my case, cheating somewhat as I use those one-cup filter things) and then slowly sipping is just marvellous. A few minutes later and I feel something I can only describe as a tiny happy spark, enabling me to start writing instead of blankly staring at the screen. If I over-do it and have a few too many cups then I may get palpitations, a little anxiety or a headache - perhaps all three if I've really gone overboard. I also get these if I don't drink any coffee, or drink less than usual. Caffeine, for me, is a wonderful substance and really helps me to be productive and happy. Pamela Hallam, Wigston Magna, Leicestershire
19. My caffeine intake has been seriously extreme because I like coffee so much. In fact, I have somehow managed to almost poison myself with it. I drank two pots a day of extremely strong coffee I made myself plus one small cup of Starbucks dark roast, plus I ate coffee beans like peanuts. I developed extreme sweating in 2008, and then last November, a very bad rash in my sweat glands (Grover's disease) due to extreme diuretic effects. Skin peeling required massive cortisone doses. Finally the doc asked if I sweat a lot.
- Me: "Yes, a lot, an extreme amount."
- Doc: "What do you drink?"
- Me: "Coffee."
- Doc: "How many cups a day?"
- Me: "Wrong question, you should ask how many pots a day."
- Doc: "We may have found the problem."
Now, back to two and a half cups a day with few side effects and sweating is much better. Rash and itching is better but not gone yet. Tried decaf, meh, drek, why bother. David O'Hara, Tallahassee, FL USA
20. I probably drink the equivalent of five or six cups a day. Hard to tell. Load up the coffee machine for breakfast, large mochachino on the way into work, and the coffee machine for the rest of the day. Think I'm joking? Look at the time I posted at [5:12am]. I can quite happily stay awake all night, although the caffeine hangover... "Caffiend", Belfast, Northern Ireland
21. I drink about 10 cups of coffee every day. I make a large cup in the morning for the drive into work. After a morning workout I brew a pot of coffee and drink almost all of it throughout the day. If I don't drink coffee during the day I will usually get a headache late in the afternoon. I am only 24 but for the seven years that I have been drinking coffee the effects of the caffeine have diminished. On a particularly draining day I can finish off a cup of coffee and then put my head down and take a quick nap. I have had to go without coffee for a month and am able to adapt just fine. I would say that I am a connoisseur of coffee. I genuinely love the taste of a good cup and don't like to drink sub-standard coffee (of course that is solely up to my judgement). When I really need a boost of energy, I do turn to a Red Bull or Monster energy drink. I guess the way I see it is that I would rather sit and enjoy a quality cup of coffee rather than pound an energy drink to feel pumped up. Chris Reid, Colorado Springs, US
22. After some 30 years of constant coffee drinking, I have arrived to the conclusion that it is, just the very best idea catalyser. Emilio de los Raos, Merida Yucatan, Mexico
23. For me one cup of green tea a day is enough caffeine, I get hyper and shaky with more. Also, green tea helps me with migraine prevention - caffeine is something that can both cause and cure migraine in some sufferers. Ruth, Halifax, UK
24. I'm an architecture student, I must confess coffee intake enlarges my work output. I drink one cup a day, when I exceed my limit, my arms start to vibrate vigorously. Taiwo Aiyepe, North Cyprus
25. About 20 years ago, due to a very high stress job with long hours, I consumed massive quantities of caffeine. I would make a jug of filter coffee and then pour it back through with a fresh filter of coffee and then drink it with a couple of ProPlus tablets. I did this for more than a year and by the end of it, if anyone was dumb enough to come anywhere near me before I'd drunk at least three mugs of coffee, they did so at their own risk. I was irritable, rude and downright unhelpful if I hadn't had my caffeine fix. I needed more and more just to get though the days and nights. After being made redundant, I went cold turkey. If what I went though is anything like coming off harder drugs, then those people have my every sympathy. Hot and cold flushes, shaking, cold sweats. Today I still drink coffee but in much smaller quantities (maybe three cups a day) and I find that it has no effect on me at all. Alasdair Carnie, Wollaston, Northants