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Caffeine: uses, dosage and background

Siski Green / 26 February 2020

Caffeine is the most popular drug in the world, used in coffee, tea, chocolate, guarana, soft drinks and some medicines for cold or flu symptoms.

Two cups of coffee on a table
The effects of caffeine can last for more than six hours

Without even realising it many of us ingest caffeine on such a regular basis that if we suddenly had to stop, it’s likely we’d suffer mild withdrawal symptoms. Both tea and coffee contain caffeine, in different amounts, and many of us rely on a cuppa not only in the morning but throughout the day too. The substance itself can be extracted from more than 60 plants and can also be man-made. The most common usage in daily life is, however, via tea or coffee, and, in lesser quantities, in chocolate.

What is caffeine used for?

The most obvious way people ‘use’ caffeine is to be more wakeful. It’s a stimulant. Many people have tea or coffee in the morning to help them ‘wake up’ while others use caffeinated drinks to wake up in the afternoon, or energy drinks before a workout, for example. Others, who don’t like coffee or tea, might take caffeine supplements instead.

Caffeine is also often touted as a tool for weight loss, and research also suggests it might help preventatively with diseases such as Alzheimer’s and dementia.

What’s the history of caffeine?

Coffee has been around for thousands of years. It’s known to have been a common drink in the 6th century in Arabia, Turkey and northern Africa. Coffee only really reached European shores fully in the 17th century and after that plantations were established in other parts of the world to supply that need – in Indonesia and the Caribbean, for example.

What’s the best way to take caffeine?

Depending on your need, you can ingest caffeine via tea or coffee, drinking an energy drink, or using supplements which will have a more dramatic effect. There are other options too – yerba mate, soft drinks and cocoa drinks also contain varying amounts of caffeine.

Caffeine content of coffee or tea varies according to the plant. To compare, the arabica bean contains around 1% caffeine, while robusta contains 2.2%. A substantial difference. An espresso contains around 200mg caffeine, a tall latte with one shot contains around 77mg, usually. To compare, a caffeine supplement usually contains between 50 and 100mg per tablet.

When you drink coffee or tea, however, you also benefit from other substances contained in the bean or the leaf, whereas a caffeine supplement may not contain those ingredients.

There are also many medications that take caffeine too, such as those for colds and flu, so check the label if you want to avoid caffeine or if you’ve already ingested enough.

Does caffeine really work?

Caffeine is an effective stimulant. It works by binding to adenosine receptors in the brain. Adenosine works by supressing arousal and promoting sleep – by binding to those receptors the caffeine blocks adenosine, stimulating your brain to release adrenaline. The result? A burst of energy and wakefulness for you.

While many claim that caffeine helps supress appetite, it hasn’t been shown to be especially effective at helping people lose weight or keep it off. A 12 year study published in the American Journal of Clinical Nutrition on caffeine and weight gain found that coffee-drinkers were less than 1lb lighter than other non-coffee drinkers at the end of the study period. Caffeine can, however, give you an energy burst while working out and in that way you would be more likely to burn more calories which in turn would aid weight loss.

Caffeine also seems to have a protective effect against Alzheimer’s and dementia, with research published in the Journal of Alzheimer’s Disease showing that drinking 3-5 cups of coffee per day at midlife reduced the risk of dementia or Alzheimer’s disease by 65% later in life. Researchers suggest this could be related to antioxidants in coffee or increased insulin sensitivity.

How long does caffeine take to work?

Once you’ve had a cup of a caffeinated beverage it goes into your bloodstream and from there takes around ten minutes to have an effect.

If you feel like you can’t function in the morning without coffee it could be a sign that you’re not sleeping properly too. It shouldn’t be necessary for normal functioning, but rather an additional boost.

What are the side effects of caffeine?

One disadvantage of the boost to energy and alertness caffeine gives is that it can prevent you from sleeping properly. If you have a coffee in the late afternoon, for example, you might still feel its effects hours later making it difficult to nod off.

It takes around six hours to halve the amount of caffeine in your body, so if you had a cup of coffee containing 200mg at 11am, by 5pm you’ve still got 100mg floating around in your bloodstream. By bedtime at 11pm, there’s still 50mg. So you can see why it might prevent quality slumber. Aim to steer clear of all caffeine after midday to ensure you sleep well if you have trouble getting or staying asleep. Remember, however, that each person’s response to caffeine is different – some people get jittery with just one cup, while others seem to be able to drink coffee without it interfering with sleep at all.

Caffeine also triggers our pleasure centres in the brain, releasing dopamine, so it’s easy to become addicted to that ‘high’ and drink more and more, chasing that feeling. Drinking coffee in large amounts daily won’t keep giving you that same good feeling, however, and you’ll simply become dependant on it, as with many other stimulants, which then could lead to withdrawal symptoms if you’re forced to go without.

Another common side effect is on your digestive system. Caffeine is a mild diuretic so you might find you need to visit the bathroom soon after having a cup or two; and it also can work as a mild laxative too by stimulating your colon.

Are there any contraindications when taking caffeine?

Blood pressure and heart rate are affected when ingesting caffeine products so if you have recently suffered heart problems, it is best to avoid caffeine or ask your GP if you can ingest low doses. Ulcers caused by stomach acid as well as issues with your colon and small intestine, as well as liver disease, may be impacted by caffeine intake too. See your GP if in doubt.

Need to talk to a GP from the comfort of your own home? Saga Health Insurance customers can talk to a qualified, practising UK GP 24 hours a day by phone. Find out more about our GP service.



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The opinions expressed are those of the author and are not held by Saga unless specifically stated. The material is for general information only and does not constitute investment, tax, legal, medical or other form of advice. You should not rely on this information to make (or refrain from making) any decisions. Always obtain independent, professional advice for your own particular situation.