The health impact of coffee is hotly debated - and studied. Ellie Broughton asks whether the drink is more than just a brief caffeine rush and why it matters?
Morning fogs part, spirits lift and the idea of work becomes a probable reality - anyone who has had a strong cup of morning coffee knows the welcome impact it can have on the body. A cup too many, however, and the coffee shakes tell us something else.
Most of the drink’s clout comes from caffeine, a stimulant that is a natural chemical in coffee beans - one that only becomes toxic at very high doses, between 50 and 200 cups of coffee over 24 hours. More positively, caffeine is known to improve concentration in the face of tiredness, as well as sporting performance, co-ordination and focus. Yet this is some way off saying coffee is an active health benefit. Indeed, the public assumption seems to be the opposite.
“It’s not the coffee that’s unhealthy in itself - a mug of coffee by itself is even virtually fat free and contains just 15 or 16 calories a cup. It’s only once you add cream, milk and syrups that it’s fattening, and the bigger problem is the associated behaviours, such as the cigarette and the bun that might go with it.” counters Sarah Schenker, dietician and member of the Nutrition Society. “But there has also been a massive escalation of research into coffee and its health benefits.
Sometimes the association between almost every condition you can think of and coffeedrinking is strong, and sometimes it’s weak - but it doesn’t seem that moderate coffee consumption has a link with any of these diseases.”
Certainly complications in studying caffeine’s effects only add to the confusion. A study published last year asserts that coffee wards off depression in women. From a large study of more than 50,000 women, researchers in the US found that women who drank two or more cups of coffee a day were less likely to get depressed.
More closely examined though, and it seems the study relied on self-reporting, meaning that the women taking part not only had to remember and report what they’d been drinking, but also whether they had depression or not. Then there is the possibility that reverse causation influenced the results: rather than coffee protecting women from depression, it could be that depressed women drank less of it.
Experts were again unconvinced by research conducted by scientists in Utrecht, Holland, and published in 2009, promising a link between coffee and a reduced risk of developing type 2 diabetes. Diabetes UK was especially unimpressed by their findings. Dr James Pickett, a research officer at the charity, noted at the time that it was “impossible” to know what other factors might affect a person’s risk of developing the condition. The development of type 2 diabetes is strongly linked to lifestyle and according to the charity, the best way to reduce your risk of developing it is taking regular exercise and eating a healthy balanced diet.
The Department of Health’s only warning is to limit consumption to five single espressos a day
As for coffee proving a benefit - the jury remains out. Its negative impact on health may be no less assured. Most evidence suggests regular consumption of coffee has, for example, no significant relationship with the risk of cancer at any site and the Department of Health’s only warning is to limit consumption to less than 500mg of coffee a day - five single espressos, six cups of brewed coffee or seven cups of instant (and 200g or less of caffeine from all sources a day if pregnant). But that doesn’t exactly frame coffee as a boon to long life either.
Might the two most recent studies offer any stronger connection between coffee consumption and health benefits? A paper published by researchers from Sweden in September suggests that coffee has a preventative effect against strokes. The survey was actually a meta-analysis of 11 studies, which included more than 10,000 cases of stroke in a total 479,689 participants.
In conclusion, the study’s authors suggest that consuming coffee in moderation is unlikely to increase risk of stroke - but nor did the the study prove that coffee directly decreases the risk either. Drinking in moderation, eating less, moving about more and stopping smoking, in contrast, do help lower the risk of stroke - if you want to drink coffee, no problem.
A second coffee study published by Swedish researchers, also last year, seems more confident in its conclusions. It has found an association between coffee and one kind of breast cancer. Around one in four women diagnosed with breast cancer will have oestrogen-receptor negative breast cancer, which is often resilient to drug treatment and requires intensive chemotherapy. Researchers led by Dr Jingmei Li surveyed nearly 6,000 women and found that drinking more than five cups a day could halve a woman’s risk of developing this type of cancer.
“But before I would go to tell my neighbours to start drinking more coffee, I would like to know what biological mechanism is at work, and that’s not yet clear,” explains a cautious Dr Li. “The goal would be to try and discover what it is in coffee that may be beneficial.”
Indeed, Dr Li admits that we don’t yet know what kind of coffee protects against ER-negative breast cancer, and we don’t yet know if coffee directly affects breast cancer risk. While we might know these things in future, she concludes, there’s no point changing your habits now: there’s simply not enough evidence yet that coffee or caffeine has a major impact on your health, for good or ill.
Cancer Research has responded to this and other surveys more bluntly still - by writing that the data for the link between coffee and breast cancer are “all over the place”. At the moment, it seems like the strongest link between coffee and cancer is the Macmillan Coffee Mornings fundraising campaign. So, more lab work is required either before we’re repeating the mantra that a few cups a day keeps the doctor away or before your latte cup comes with a big red government health warning.
For many, this status quo is just fine - if caffeine was found to be dramatically good or bad for you, then you would also have to watch your tea, cola and chocolate consumption as well as your espresso habit. But with coffee consumption on the up, there is growing interest in finding out. Like a filter coffee machine, expect a steady drip of new scientific revelations - some more convincing that others - over the coming years. Keep the PG Tips to hand just in case.