Quick Guide to Caffeine


Caffeine and in particular, coffee, is a topic that a lot of my nutrition clients ask me about. If you struggle to do without your daily fix of tea or coffee, it’s worth remembering that caffeine is a psychoactive drug. In other words it belongs to the same class of drugs as LSD. So it’s not really surprising that it’s addictive!

Caffeine is a naturally occurring chemical found in plants. As well as coffee, it’s found in cocoa beans and tea leaves. It is also extracted and added to food, drink and some medicines. Caffeine is a central nervous system stimulator. It causes an increase in certain brain chemicals that can change your mood and behaviour. It’s no wonder that so many people are hooked on it. It’s not all bad though!

Can caffeine be good for you?

First let’s start with the benefits.

  • The caffeine found in dark chocolate, coffee and tea is accompanied by antioxidant rich plant chemicals called polyphenols. These are anti-inflammatory. They are therefore highly beneficial because inflammation drives most chronic diseases today. Interesting fact – a cup of coffee contains 2 and a half times more polyphenols than tea!
  • Caffeine stimulates cognitive function and memory. It makes you more alert, relieves fatigue and improves your concentration. It does this by stimulating the release of two important brain chemicals dopamine and noradrenaline.
  • Caffeine may improve athletic performance.
  • Caffeine increases metabolism and fat burning.

And the not so good…

  • Caffeine impairs the absorption of nutrients such as iron and calcium
  • Caffeine is dehydrating and it makes you pee more . This leads to increased loss of certain  nutrients such Vitamin C and B complex and potassium.
  • Caffeine is linked with acid reflux and increased production of stomach acid and therefore ulcers. It speeds up the rate at which food mixed with acid leaves your stomach. This means it enters the first part of the small intestine more quickly and the acid can cause inflammation in the small intestine.
  • Caffeine can trigger migraine and raise blood pressure in people who are susceptible
  • Caffeine negatively affects the time it takes to get to sleep and sleep quality
  • Caffeine consumption has long been linked with anxiety. Caffeine-induced anxiety disorder is a recognised diagnosis. It is known to make anxiety disorders worse and to trigger panic attacks in people with a history of panic attacks.
  • Caffeine is thought to play a role in psychiatric disorders. A study from 2003 concluded that “Assessment of caffeine intake should form part of routine psychiatric assessment and should be carried out before prescribing”
  • In pregnant women, It is known that caffeine crosses the plancenta to reach the foetus. It seems from research that caffeine, at certain levels, affects the growth of the baby in the womb and may increase the risk of miscarriage or stillbirth or giving birth to a low weight baby.
  • Finally when it comes to coffee, we must not forget all those things that might be added like cream, sugar, chocolate etc. This can hike the calories up to as much as 500 for one frappacino, for example!


How much is okay?


How much is good for you very much depends on your individual caffeine tolerance.

UK guidelines for caffeine consumption are 400mg maximum daily and no more than 200mg in pregnancy. 400mg is about 4 medium to large cups of coffee.

However, these are very general guidelines and it very much depends on individual caffeine and the type of health issues you have.

For a start, your body weight is a big factor. If you weigh 8 stone you will tolerate about 200mg less caffeine daily  than someone weighing around 16 stone.

If you suffer from anxiety, panic attacks or nervous problems, you’ll be much more sensitive to caffeine’s effects.

As caffeine depletes B complex and other nutrients, if your levels of these nutrients are not optimal in the first place, you could experience symptoms relating to deficiency. For example, lack of B vitamins contributes to tiredness and mental health problems.

How efficient your liver is at metabolising caffeine is another important consideration.  Just as some people have a higher alcohol tolerance, the amount of caffeine we can manage without ill effects varies.

So if you are feeling very tired, wired, anxious or depressed, keeping your caffeine intake much lower than 400mg daily,  will likely be of benefit.

How long does it take to get caffeine out of your body? 

Caffeine is thought to have a half-life of about 6 hours.  A Half life is how long it takes for half of the drug to be metabolised.  So if you consumed 150mg caffeine at 11am you would still have 75mg left in your body at 5pm. But this does vary from one individual to another.


  • For every caffeinated drink, drink a large glass of water to help flush the caffeine out.
  • Keep caffeinated drinks at least one hour away from meals to reduce the likelihood of iron and calcium absorption being blocked.
  • Take a B complex with vitamin C if you drink a lot of tea and coffee to replace lost vitamins
  • If there is osteoporosis in your family history, think about your calcium and magnesium intake from food and supplements.
  • Don’t forget unexpected sources of caffeine. Check the label of over the counter painkillers as some contain up to 130mg caffeine per tablet.
  • Coffee brewed through a paper filter contains less cafestol, a substance in coffee that raises LDL cholesterol. Other types of brewed coffee contain more cafestol.
  • If you are making your own tea and coffee, brewing it for less time will reduce the caffeine content.
  • Fresh coffee is preferable to instant. Whilst instant contains less caffeine it contains higher levels of acrylamide. Acrylamide is formed during the roasting process and has been linked to cancer. It does occur In other foods as well such as well done toast, cereals, chips and crisps. Incidentally cereal based coffee substitutes contain much higher levels than real coffee!
  • Avoid caffeine from mid afternoon onwards.
  • If you have high blood pressure, anxiety or depression, consider drastically reducing your caffeine.
  • If you are pregnant, restrict your caffeine intake (NHS guidelines are 200mg in pregnancy). Avoid caffeine altogether if you are susceptible to miscarriages.


The caffeine content below is for an 8floz tea or coffee (except for espresso). 8floz is the small size in most coffee chains. There can be a lot of variation in the caffeine content of different brands of tea and coffee. For example there was a study on several brands of green tea which involved brewing each of the teas for exactly the same time. The caffeine content of each cup of tea varied from 47mg down to 12mg! Of the coffee chains, Starbucks seems to be the only company who are  transparent and helpfully list the caffeine content of all their coffee.

Starbucks caffe latte 75mg

Starbucks cappuccino                                                                                   75mg

Starbucks decaff                                                                                            12mg

Starbucks filter coffee                                                                                   157mg

Starbucks Espresso single shot 75mg

Caffe Nero espresso single shot 84mg

Costa espresso single shot 92mg


Decaff instant coffee                                                                                      2.5mg

Regular instant coffee                                                                                    57mg


Green tea 25mg +

PG Tips 56mg


85% cocoa solids dark chocolate100g bar 81mg


Pepsi max 330ml can 42mg

Diet coke 330 ml can 42mg

Coca cola classic                                                                                             31mg

Pepsi regular                                                                                                   35mg

Anadin extra (1 tablet)                                                                                   45mg


Well done on finding time to read to the end! I hope you found it informative.