There’s more to a cup of coffee than just an early morning pick-me-up.
By Michael Mosley
As I stagger out of bed in the mornings and begin my ritual of resistance exercises (press-ups, squats, sit-ups and the dreaded plank) the one thing that keeps me going is the promise of a lovely cup of tea when I get downstairs. After my first cup I take the dog for a walk, soak up the sunshine, then sip my first coffee of the morning, normally drunk black.
Apart from the flavour, what I love about tea and coffee is that they’re stimulants, rich with the world’s most widely consumed psychoactive drug, caffeine. A white, crystalline powder, it’s produced by plants to protect them against insect attack.
Not only do tea and coffee perk me up in the mornings, but there is strong evidence that caffeine consumers enjoy a range of other health benefits, with the benefits being clearer for coffee than tea.
A massive review of studies, ‘Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes’, published in the British Medical Journal, which looked at more than 220 studies, found that drinking coffee was associated with a significantly lower risk of heart disease and cancer, possibly because it’s rich in antioxidants and other anti-inflammatory compounds. Coffee drinking was also associated with a lower rate of Alzheimer’s and Parkinson’s disease.
Based on this and other studies, the best ‘dose’ is between two and five cups a day. In terms of health benefits, the studies don’t distinguish between instant coffee and brewed, but when it comes to caffeine content, a cup of instant coffee contains between 60-80mg of caffeine, while freshly brewed contains 60-120mg. A cup of tea, on the other hand, comes in at around 40mg of caffeine, depending on how long it’s been brewed.
As with most things, however, more is not necessarily better. Drink more than five cups of coffee a day and the benefits tend to drop off. It’s also unwise for pregnant women to drink lots, as it’s linked to a slightly higher risk of prematurity and miscarriage.
Another downside to coffee, when it’s drunk at night, is that it keeps some people awake. I’m sensitive to caffeine, but I also clear it from my system very fast, so I can drink coffee in the evening with no problems, while one cup in the afternoon has my wife twitching. The half-life of caffeine (the rate at which your body will clear half of what you’ve consumed) is anything from two to twelve hours and is largely dependent on your genetics and a liver enzyme called CYP1A2.
One of the things I should probably do is drink my coffee before my morning exercises, as studies show that coffee makes resistance exercise feel easier and reduces symptoms of fatigue. But I love the ritual of drinking coffee after a brisk walk too much to want to change the order, whatever the science suggests.
[Source: BBC Science Focus]