We are a nation of coffee addicts — last year alone we spent almost £1 billion on it. Our caffeine habit was vindicated last week when Swedish researchers revealed women who drink five or more cups a day could be protecting themselves against an aggressive form of breast cancer.
But with other research suggesting high doses of caffeine can pose risks to health, just how much coffee should you be drinking a day? To help you decide, we reveal the benefits — and risks — of your daily intake.
PROS: Drinking just one cup of a coffee a day could reduce your blood pressure, according to a Greek study of 485 people aged 65 to 100.
The researchers found those who drank between one and two cups daily had the healthiest arteries.
The scientists believe this is due to antioxidants in the coffee increasing the production of nitric oxide, a compound found naturally in the body. Nitric oxide helps relax artery walls, and lowers blood pressure.
And a single cup could boost your brainpower, too: a Bristol University study of 600 people found those who had a cup of regular coffee performed better in mental tests than those who drank decaffeinated coffee or nothing.
This may be because caffeine causes more sugar to travel to the brain, giving it extra energy and creating a temporary ‘lift’, says Dr Sarah Schenker, a dietitian.
CONS: Even one cup during the day could keep you counting sheep late into the night, says Sian Porter, of the British Dietetic Association. It takes around eight hours to completely remove caffeine from the body, she explains, so don’t drink a cup after 3pm to 4pm if you suffer from sleep troubles.
PROS: This amount of coffee a day could keep Alzheimer’s at bay, say scientists from the University of Florida. Although the findings came from animal research, the team say that around 200mg of caffeine, the equivalent of two cups of coffee, could help prevent the build-up of proteins in the brain that have been linked to memory loss associated with the disease.
And drinking the equivalent of two cups of coffee 30 minutes before exercise may enhance your performance by providing you with more energy, suggests a study in the International Journal of Sports Medicine.
‘It stimulates the production of fatty acids in your body which you use for fuel — it’s like opening the cap on your reserve tank,’ says Dr Schenker.
CONS: ‘If you’re pregnant, your upper caffeine intake limit should be 200mg, or two cups of regular-strength coffee,’ says Dr Schenker.
‘It’s thought the caffeine causes the body to release high levels of the stress hormones cortisol and adrenaline, which could increase the risk of miscarriage.’
PROS: The caffeine intake from three cups a day can reduce the risk of developing ovarian cancer by a fifth, the American medical journal Cancer reported in 2008.
After studying more than 122,000 women, researchers found the benefits were even greater for women who’d never been on the contraceptive pill or HRT (their risk was reduced by 35 and 43 per cent respectively).
Men who drink three cups of coffee have a 40 per cent lower risk of developing gallstones, according to a study published in the Journal of the American Medical Association. The scientists believe the caffeine stimulates contractions in the gall bladder, helping to remove any small stones before they become a problem.
CONS: Coffee drinkers who have more than three cups a day may increase their risk of heart attack, a U.S. study in 2006 found.
‘After around three cups of coffee, your heart will beat noticeably faster, raising blood pressure slightly,’ explains Dr Schenker.
And bizarrely, drinking just three cups of a coffee a day may make some women’s breasts shrink, according to researchers from Lund University in Stockholm.
The scientists surveyed almost 300 women about their bust size and coffee consumption, and found a clear link between drinking three or more cups of coffee daily and smaller breasts. The effect of caffeine on oestrogen levels could be responsible for the results, say the researchers.
PROS: There is 400mg of caffeine in four cups of coffee and this amount is thought to provide the maximum benefit of coffee’s disease-combating antioxidants.
‘Tea and coffee are packed with antioxidant polyphenols, which can potentially cut the risk of cancer,’ says Dr Michelle Harvey, research dietitian at the Genesis Breast Cancer Prevention Centre, University Hospital of South Manchester NHS Foundation Trust.
‘Studies show it promotes production of a less potent form of the cancer-causing hormone oestrogen,’ she says.
University of Utah scientists found people who drink four cups daily are 39 per cent less likely to suffer from cancers of the mouth and larynx.
Other research suggests this amount may also reduce the risk of developing colorectal and prostate cancer, as well as type-2 diabetes.
CONS: People who drink this amount are twice as likely to develop rheumatoid arthritis.
Researchers believe coffee may increase the levels of compounds in the body that can lead to inflammation and joint pain.
PROS: Researchers at the National Cancer Centre in Tokyo found that drinking five cups of coffee reduced the risk of serious liver damage by three quarters.
Their findings were based on a study of 90,000 middle-aged men and women over ten years.
The scientists believe antioxidants in the coffee may be responsible for the protective effect.
CONS: Several studies have shown that this amount of coffee is a risk factor for osteoporosis, as caffeine can interfere with the absorption of calcium.
However, many experts dispute this, and the National Osteoporosis Society says there is no conclusive evidence that coffee thins bones, but advises no more than five cups to be safe.
SIX OR MORE CUPS
PROS: Drinking six or more cups a day can reduce the risk of some skin cancers by 31 per cent, according to researchers from Wayne State University in Detroit, who studied more than 90,000 women. They believe antioxidants may protect skin cells.
CONS: This amount of coffee can lead to dehydration, says Dr Schenker. ‘The coffee causes excess fluid to be lost from the body. This speeds up the elimination of minerals and vitamins — one of the key vitamins it depletes is B6, vital for preventing kidney stones.’
It can also cause the body to release hormones that, linked to anxiety and stress, can lead to irritable bowel syndrome, increase blood pressure and in turn, the risk of cardiovascular illnesses.
‘The constant “fight-or-flight” response this amount of caffeine has on your body can definitely have severe health implications,’ she adds.
By MATTHEW BARBOUR
Last updated at 8:17 AM on 18th May 2011