Caffeine attracts its fair share of controversy. From reducing our chances of conceiving to impacting our cholesterol levels, the health headlines on caffeine often paint it as a poison. Detox gurus and many nutritionists also advise the elimination of coffee, tea and chocolate specifically because of their caffeine content, while celebrity detox diets churned out in many women's magazines give the substance scathing reviews.
And certainly, like any product consumed excessively, a raised intake (more than 400mg per day) of this pharmacologically active compound can have negative effects on the body - think mood swings, sleep interruptions, migraines and raised blood pressure (though only short term). It is also considered a mild gut irritant, and contributes to premenstrual fluid retention. Withdrawal symptoms can include anxiety and irritability. Although these symptoms occur only if the daily caffeine levels are exceeded, the substance is still perceived as a poison.
"Caffeine gets hammered a lot by many nutritionists, but I've looked at the evidence about caffeine being detrimental to health, and it seems that problems only arise at high doses," says nutritionist and researcher Dr Carrie Ruxton. She points out that tea and coffee can also contain high levels of antioxidants, which may help protect against cancer.
In fact, it is the antioxidant content of many caffeinated products that has been making headlines lately. Coffee, tea and chocolate are all high in a number of plant compounds including antioxidants, which the latest research says can boost our immune systems and even protect against some cancers.
Recent studies have suggested that three cups of coffee a day can help slow memory loss associated with Alzheimer's (due to its stimulatory effects). Caffeine is also said to lower risk of developing type 2 diabetes by about 25 per cent.
Although the anti-caffeine headlines have listed the substance as harmful to our hearts and increasing our risk of developing cancer, this has yet to be proven. The bulk of the evidence suggests that moderate, regular consumption (300mg daily) of caffeine does not adversely affect health. There is no known association with cardiovascular disease or cancer. So removing caffeine from your diet - like excluding dairy, wheat and sugar - is not really the pro-health choice.
"Telling people to avoid caffeine has become a mantra among certain healthy-eating gurus," explains Dr Ruxton. "But being told to eliminate caffeine, sugar, dairy, wheat and yeast doesn't leave many options to those who want to eat well and yet enjoy their food. I feel it's time to rehabilitate caffeine - and stop instructing consumers to avoid it."
Indeed, in modest quantities, caffeine can provide the kind of benefits you'd least expect. So before you eliminate it from your diet, and miss out on a nice cup of tea and a well-deserved chocolate bar at the end of the day, read on to discover how a little caffeine can be good for you.
1. It makes us more agreeable
In research published in the European Journal of Social Psychology in 2006, scientists from the University of Queensland revealed that moderate intakes of caffeine can make us more likely to be swayed by a positive argument.
Researchers carried out experiments on 140 volunteers who were quizzed about their views on controversial topics like euthanasia. They were asked to read arguments in support of the view opposing their own.
Those who had been given orange juice containing caffeine were more likely to change their opinion than those who had been given orange juice without caffeine. This suggests that caffeine allows us to process a persuasive argument more efficiently.
2. It fights cellulite
Yes, there's a very good reason why the cellulite creams that work contain caffeine. "When applied topically in an alcohol-based formula, caffeine penetrates the skin and stimulates the fat cells to liberate their fatty acids, reducing cellulite," says cosmetic medicine practitioner, Dr Elisabeth Dancey.
"Drinking tea and coffee can also have a positive effect on [reducing] cellulite as up to two cups a day will increase the body's metabolic rate. But caffeine is a double-edged sword where cellulite is concerned. Any more than two cups and you risk damaging the micro-circulation leading to a decreased elimination of toxins, which can result in more cellulite."
3. It can reduce the risk of asthma attacks
It has been known for more than a century that caffeine can help those susceptible to asthma to breathe more easily. French writer Marcel Proust, an asthmatic, wrote how as a child in the late 1800s, caffeine "was prescribed to help me breathe". Several modern-day studies appear to confirm the long-held suspicion. Drawing from six clinical trials in the subject, researchers involved in a 2007 study in the Cochrane Database of Systematic Reviews found that caffeine helped relax airway muscles and produced improvements in airway function lasting up to four hours. An Italian study of over 70,000 people revealed an inverse association between asthma symptoms and coffee intake, with the risk of an attack falling by 28 per cent in those consuming three or more cups daily.
4. It can help fight pain
Ever wondered why the painkillers to take for a headache contain caffeine? It's due to the fact that caffeine boosts the medicine's ability to act. It appears to improve the absorption of the painkiller, helping it to work more effectively. Anecdotal reports suggesting that a cup of tea or coffee can help clear up a mild headache have been supported by a few modest studies. Indeed, it is known that vasodilators (chemicals that dilate blood vessels - such as alcohol) can induce headaches, and that vasoconstrictors (chemicals that constrict blood vessels - such as caffeine) can relieve them. Some have expressed concern that caffeine is added to painkillers, but the advantage is that it may lower the dose required to offer relief, and so potentially decrease the likelihood of dependence. In a small study, scientists from the University of Georgia in the US found that drinking coffee was more effective in reducing muscular pain during hard exercise than taking an aspirin.
5. It may protect against liver disease
A study of almost 10,000 volunteers conducted by the National Institute of Diabetes and Digestive and Kidney Diseases in America revealed that consuming caffeine in tea or coffee may reduce the risk of liver damage in heavy drinkers and in people who are overweight. Another study from Norway also suggests that three cups of coffee per day may reduce death rates from cirrhosis of the liver. More recently, a study published in the Journal of Hepatology in 2010 found that 300mg of caffeine from coffee each day offered strong protection effect against liver fibrosis or scarring.
6. It can boost physical performance
Numerous studies have linked caffeine to improved physical performance: the International Olympic Committee even has a limit to the quantity an athlete can have in his or her system during competition. Caffeine appears to allow athletes to extend their peak performance times and enhances endurance. In a 2009 review of more than twenty studies published in the Journal of Strength & Conditioning Research, scientists concluded that caffeine intake was an effective physical performance and recovery enhancer for endurance athletes, when taken before or during exercise in moderate quantities. They also found that abstention from caffeine a week prior to an event improves its effect.
7. It boosts mental function and alertness
A team led by Professor Andrew Scholey of the Human Cognitive Neurosciences Research Unit at Northumbria University, England, has been researching the effects of caffeine intake on mental functioning. In one study, volunteers were divided into two groups: those who normally drank the equivalent of several cups of coffee daily, and those who consumed virtually no caffeine at all. Each group was given equal quantities of caffeine and was subjected to cognitive testing. The results showed that caffeine positively affected both groups equally. "We expected the benefits of caffeine to be down to the alleviation of withdrawal symptoms," Professor Scholey says. "But it looks like it's not. Our results prove that the caffeine in a cup of coffee improves alertness, makes you perform and concentrate better, and gives you quicker mental recall."
8. It protects the brain against cancer
In a large study published in the American Journal of Clinical Nutrition in 2010, British researchers from Imperial College London found that tea and coffee drinkers were considerably less at risk - over a third less likely - to develop a brain tumour. The research involved more than 400,000 individuals from across Europe. While some experts speculated that the antioxidants in tea and coffee offered some protection, the researchers also suggested that the caffeine can help mildly restrict blood flow to the brain, hindering the growth of potential tumours.
Unless caffeine has been specifically added to a product (as in painkillers or energy drinks) it will not be listed as an ingredient - for example, in coffee or chocolate, so do check.
How much is too much?
300mg is recommended for normal, healthy adults, with the aim of staying below 400mg
200mg is the recommended limit for pregnant women