Gill Stannard

Monday, February 04, 2008

caffeine - benefits and harms

Caffeine, a xanthine alkaloid, appears in some of our favourite foods and beverages in various forms including coffee, tea (green, black and white), cola, ‘energy’ drinks, cocoa, chocolate, guarana and mate. It is also added to some pharmaceutical drugs and is available in popular over the counter stimulants.

Physiologically, caffeine has a stimulant effect on the body. It increases nerve cell activity in the brain and triggers the pituitary gland to release more adrenaline (also known as epinephrine, the ‘fight or flight’ hormone). Some of the effects include an initial sense of alertness, increased cardiac activity (heart beats faster) and a release of glycogen (stored sugar) giving us an energy boost. The first cup or two of caffeine may have what is perceived as being a positive effect on wellbeing, helping us think more clearly and act faster, those these benefits are reversed with increased intake. If you are already stressed, the added adrenaline will potentiate this state – increasing your chance of panic attacks, palpitations, insomnia, sweating etc.

However – as we are all individuals this can have different effects on us depending on how long it takes to metabolise caffeine, such as age, various medications and health of the liver. For example the half life (how long it takes the body to clear half of the caffeine from the body) in a healthy adult is about 3-4 hours, in a woman taking the oral contraceptive pill that increases to 5-10 hours, while in a pregnant woman it is up to 11 hours. The half life for a baby in utero or a newborn is even higher, so that even on one decent cup of caffeine a day via the mother’s milk the neonate may not have got rid of yesterdays intake fully before today’s hit.

Much of the conjecture as to whether caffeine may be harmful or beneficial comes down to genotype, how your individual blueprint dictates your metabolism of certain drugs. In science speak, it is all to do with your variant of the cytochrome P450 enzymes. Current wisdom deems that it is your variation of this enzyme that effects how you utilise caffeine (CYP1A21A allele are "rapid" caffeine metabolisers, whereas carriers of the variant CYP1A21F are "slow" caffeine metaboliers). For example see this study on caffeine metabolism and heart attack risk.

Interestingly, as caffeine is metabolised in the liver by the cytochrome P450 (enzyme) pathway – so do a number of herbs and drugs. The reason St John’s wort (and other herbs) is contraindicated with a number of pharmaceuticals (including the contraceptive pill, antivirals, anti-rejection drugs and some chemotherapy agents) is due to competing with this same metabolic pathway. Considering the popularity of coffee etc and quantity consumed – should there be a warning label slapped on your latte or cola drink?

Want to know more? Here's a good reference on the chemistry, metabolism and addictiveness of caffeine

Because there are so many variables in the way that caffeine is broken down in the body it could explain why it affects individuals so differently, though tolerance and addiction are also key players in the caffeine picture. This delicious alkaloid has a similar effect on dopamine, one of our ‘happy hormones’, as cocaine and heroin. It also interferes with another chemical, adenosine, which may cause insomnia. With less sleep we wake up ‘needing’ our caffeine hit to get going in the morning – and so the cycle continues.

When we abstain from our daily caffeine hits, the tiredness that many people experience is actually how you felt before – only the drug was masking it. So stopping caffeine doesn’t actually make you any tireder – rather it gets you in touch with where your body is really at. Increasing the amount of water you drink and taking a good multivitamin with at least 50 mg of B6, plus a few early nights should help remedy this.

There has been a flurry of negative studies about caffeine published recently, what is most significant is they overturn previous studies (or assumptions) as to benign or even beneficial effects of caffeine. These include an increase in first trimester miscarriage at even half (200 mg) the presumed ‘safe’ dose and a harmful rise in blood glucose levels in people with diabetes.

While most obstetricians have assured women for years that a caffeine intake equivalent of 3 standard cups of coffee a day in pregnancy will not harm the foetus, (keep in mind it was only a generation or ago that smoking in pregnancy wasn’t considered harmful) a study published this year in The American Journal of Obstetrics and Gynaecology has overturned this assumption. In a well-designed study a mere 200mg (just over one decent cafĂ© cup of coffee) a day was shown to double the chance of miscarriage in the first trimester. This was shown to be even more detrimental in women who had previously had a miscarriage.

Previous studies have also shown a connection between delayed conception (ie: taking longer to get pregnant) and caffeine intake in women. Paradoxically, it may have a positive effect on sperm motility (though I have not cited the study this claim is based on).

The second negative study regarding caffeine to hit the news already this year is in connection with Type 2 diabetes. While previous investigations have suggested that caffeine may be beneficial for those with diabetes, a pilot study in this month’s issue of Diabetes Care, tracks the effects of pure caffeine (versus tea or coffee drinking) on blood sugar levels. On average blood glucose levels rose by 8% after caffeine though after an evening meal this could peak to 26%. While it had a very small sample size, considering that we already know that caffeine triggers the liver to release glycogen, there is compelling evidence that avoiding caffeine of all kinds could help diabetics achieve better control.

Other than ‘helping’ us think and act initially quicker, caffeine appears to assist bronchodilatation – meaning if you are an asthmatic at the beginning of an attack without your inhaler, a strong cup of coffee immediately may bring some relief. There are some studies that coffee drinking may also be protective against Parkinson’s disease.

Don’t forget that all forms of caffeine (even so-called ‘decaf’) can negatively impact on your absorption or utilisation of a variety of nutrients – especially calcium, protein, iron and water soluble vitamins (eg B and C) so keep caffeine consumption away for meal times and supplement taking.

Updates: Here are some other articles on interest on the topic.

Red bull - heart attack in a can?

Coffee psychosis

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