Tuesday, February 24, 2009
Caffeine & Coffee : Health Benefits
So, is coffee good for you? Or is it bad for you?
How about decaf?
It seems that there are mixed messages out there, about health effects from things such as coffee or caffeine.
What does the evidence tell us?
The evidence base is extremely compelling --
Here is a link to a study by Lopez-Garcia et al. from Annals of Internal Medicine in 2008, involving over 100 000 people, over 18 years of follow-up. Such massive studies with long follow-up time are incredibly informative:
In the study, it shows clearly that coffee drinkers have lower overall mortality rates, mainly due to a reduction in rates of cardiovascular disease. It showed a modest reduction in mortality rates associated with decaffeinated coffee as well. The authors conclude that the potential health benefits from coffee are due to components in the coffee other than caffeine.
The graph on the top is copied from the paper, and summarizes the results from the study. You can click on the graph to expand it. Actually, the data as presented on the graph suggests that people are healthier who have 2-3 cups of coffee per day, compared to those who have just 1.
Perhaps the less desirable effects from just a single cup per day are due to the more pronounced "jolt" of caffeine that would happen in a person who is not used to drinking as much coffee. Perhaps this effect would offset the health benefit, at low doses. At higher doses, the body may become more tolerant to caffeine's anxiogenic effects.
Unfortunately, this study did not look at mental health effects from drinking coffee, or from caffeine intake.
In another large epidemiological study of over 1400 people followed over 21 years, it was found that those who consumed coffee in mid-life had a substantially lower risk of developing dementia. This association was true after adjustment for demographic differences, lifestyle, and vascular disease.
This case-control study from Archives of Neurology in 2007 showed an inverse association between coffee intake and development of Parkinson disease (i.e. this relationship suggests that coffee could protect the brain from disease such as Parkinson's). However, smaller case-control studies such as this one are much weaker than the large prospective studies cited above:
The following 2008 article from Sleep Medicine Reviews presents a more cautionary account of caffeine's effects, particularly with respect to causing a dependence phenomenon, and to disrupting sleep quality. However, a lot of the data cited in this article is absurd, such as showing that a dose of caffeine immediately before sleep causes sleep disruption! Bedtime doses of coffee are not a realistic reflection of most people's caffeine intake!
Here's an interesting reference to an article showing that the tendency for caffeine to cause sleep disturbance is a heritable trait. That is, some people might be vulnerable to caffeine-induced insomnia, whereas others could sleep well regardless of their caffeine intake:
Here's a case report of a person with schizoaffective disorder improving upon discontinuing heavy caffeine intake:
In summary, it appears that coffee drinking is not harmful. In most cases, it may in fact be good for you. However, pregnant women should minimize their use of coffee. For some people, caffeine may cause or exacerbate anxiety or insomnia, especially at higher doses.