Generally, people tend to have quite firmly established ideas about weather a food is healthy or not. And they may even have some idea about which conditions a food is supposed to protect against or promote. So, for instance, when asked to comment on red meat, most people will express the view that this food is inherently unhealthy, and will often qualify this by mentioning its supposed link with heart disease and colon cancer. And when many people think of sugary soft drinks, their mind will tend to go rapidly to problems such as tooth decay and weight gain.
Another foodstuff that tends to labour under an unhealthy image is coffee. Yet, when I ask individuals what it is about this drink that is so unhealthy I find the answers can be very vague indeed. Some may mention caffeine but be unable to say what the problem might be here. Mostly, though, individuals are unable to say what it is about coffee that makes it a supposedly undesirable beverage.
One reason for this is that there isn’t actually much evidence that coffee is unhealthy. In fact, there is a fair body of evidence suggesting quite the reverse. Not so long ago one of my blog posts looked at some of the evidence linking coffee consumption with a reduced risk of certain conditions including diabetes and cardiovascular disease (such as heart attacks and stroke).
Some have suggested that the apparent health-giving properties of coffee may come, at least in part, from the ‘antioxidant’ substances it contains (including so-called ‘polyphenols’ that are found in other foodstuffs such as tea, cocoa, onions and apples).
With this background in mind, I was interested to read about a study published this week which looked at the relationship between coffee-drinking and risk of death in a group of about 86,000 women and 42,000 men. Men in this group were monitored for 18 years, while women were monitored for 24 years.
The researchers who conducted this study, from the Harvard School of Public Health, in Boston, USA, looked at the relationship between different levels of coffee consumption and overall risk of death in both men and women. In women, compared to drinking less than one cup of coffee per month, drinking at least 5-7 cups of coffee per week was associated with a statistically significant reduction in overall risk of death. In particular:
Drinking 5-7 cups of coffee per week was associated with a 7 per cent reduction in risk of death
Drinking 2-3 cups of coffee per day was associated with an 18 per cent reduction in risk of death
Drinking 4-5 cups of coffee per day was associated with a 26 per cent reduction in risk of death
Drinking 6 or more cups of coffee per day was associated with a 17 per cent reduction in risk of death
For men, no statistically significant results were obtained. However, there was a trend for increasingly lower risk of death as coffee consumption increased. Specifically:
Drinking 2-3 cups of coffee per day was associated with a 3 per cent reduction in risk of death
Drinking 4-5 cups of coffee per day was associated with a 7 per cent reduction in risk of death
Drinking 6 or more cups of coffee per day was associated with a 20 per cent reduction in risk of death
This study showed that the reduction in risk of death was, essentially, due to a reduced risk of deaths due to cardiovascular disease. So-called epidemiological studies of this nature cannot be used to prove that coffee can reduce the risk of death. However, in women at least, this study supports the notion that coffee may have real benefits for health and longevity.
One weakness of this sort of epidemiological study is that it’s not coffee drinking per se, but factors associated with coffee drinking (so-called confounding factors) that may be the real reason behind an association with this dietary habit and disease. For instance, coffee-drinking may be more prevalent among younger people, and it might be their relatively young age that is the reason for why coffee-drinkers appear to be at a reduced risk of cardiovascular disease. In this study, certain confounding factors (including age, smoking and other risk factors for cardiovascular disease) were accounted for, which strengthens its findings somewhat.
All-in-all, this study seems to provide further evidence that coffee does not deserve its quite unhealthy reputation. It also supports the idea that coffee might even have some significant benefits for health.
Lopez-Garcia E, et al. The Relationship of Coffee Consumption with Mortality. Annals of Internal Medicine 2008:148(12);904-914