Image source: http://news.bbc.co.uk/1/hi/magazine/6945697.stm (cited later on)
Caffeine is part of most people’s everyday lives (especially mine!), for the most part deliberate, although there are many places where caffeine can be found which are rather surprising (such as chocolate and decaf). Caffeine is naturally found in chocolate, coffee and tea and is added to cola, energy drinks, and medicines such as flu remedies among others. Decaffeinated coffee still contains approximately 10% of the original caffeine making the name “decaffeinated” somewhat of a misnomer. It is absorbed very quickly, usually within a few minutes, and acts to block chemical signals in your brain that tell you to feel sleepy – so you end up feeling more awake. Unsurprisingly, it has been shown in various studies that caffeine can interrupt normal sleep patterns, and that abstinence from caffeine improves sleep for those who suffer from insomnia.
Caffeine is addictive and has significant withdrawal symptoms including headaches, depressed mood, irritability, flu like symptoms, and nausea. Typically withdrawal symptoms last 2-9 days and have been reported in people who consume as low a daily dose as 100mg/day (one cup of coffee). Enough evidence of this withdrawal has been found that it has now been included in the newest version of the Diagnostic and Statistical Manual (DSM). It is possible to overdose on caffeine, with one man reportedly dying from eating too many energy mints.
All of these suggest that caffeine is a really bad component in your daily cuppa. Are there any actual positives of caffeine? Various recent studies are suggesting that there are some good reasons to include caffeine in your daily rituals so you may be able to relax a bit. One study showed that a cup of coffee before exercising can help you to exercise for longer than you would otherwise, while another showed that fat burning was increased following strength training after a cup of coffee. Specific sources of caffeine have also been investigated, with green tea demonstrating a helpful influence on muscle recovery following strenuous strength training – although that was a study on mice and human mileage may vary. Various studies have shown an improvement in cognitive abilities following caffeine intake, such as this one on information processing, and this one on the prevention of “cognitive decline” in ageing rats. A further study has found increased life expectancy for those who drink moderate amounts of tea or coffee, although this comes with the warning that high doses may lead to increased anxiety-related illnesses.
The current advice from the Food Standards Agency in the UK lists a recommended maximum daily doses of caffeine of 400mg for adults, and 200mg for women who are pregnant or trying to conceive. So how much is that? While the table below lists standardised amounts these should be taken with caution as caffeine amounts vary hugely depending on the type of bean, how the beans are roasted and how they are served. This makes for an interesting day of mental maths for most people doesn’t it?
CAFFEINE IN FOOD AND DRINK
• 1 mug of instant coffee: 100mg
• 1 mug of filter coffee: 140mg
• 1 mug of tea: 75mg
• 1 can of cola: 40mg
• 1 can of ‘energy’ drink: up to 80mg
• 1 x 50g bar of plain chocolate: up to 50mg
• 1 x 50g bar of milk chocolate: up to 25mg
So if you eat…
• one bar of plain chocolate and one mug of filter coffee, or
• two mugs of tea and one can of cola, or
• one mug of instant coffee and one can of energy drink
…you have reached almost 200mg of caffeine.
Source: Department of Health