Time to wake up and smell the Coffee

The title is not a metaphor, this is a posting that is quite literally about Coffee. Be aware that it is a substance that I consume lots of on a regular basis, so I may indeed be a tad biased. The news is that a meta-analysis of many Coffee studies has declared it to be not only safe but also potentially beneficial to your health.

Is this news yet another on-again/off-again Daily Mail type of viral ad by a coffee producer?

No, not at all, this all comes via the British Medical Journal. They have published, not one, but three related articles on the topic on the same day (Nov 22nd).

The BMJ Coffee Editorial

There is an editorial : Coffee gets a clean bill of health and there you get the big picture summary …

Poole and colleagues report findings from an umbrella review of clinical trials and observational studies of coffee intake and health outcomes … The authors concluded that coffee consumption seems generally safe within usual patterns of intake and is more likely to benefit health than to harm it.

That however does come with some additional and quite important observations …

Does coffee prevent chronic disease and reduce mortality? We simply do not know. Coffee drinking is a complex behaviour

In other words, “beneficial” is a correlation, because nobody has established a causal link here. The problem is that often coffee consumption is also associated with other things. For example smoking is a well-known association, hence when studying it, then you do need to carefully factor that in and not fool yourself into reaching a false negative conclusion.

What is also true is that if you walk into any coffee shop then often you will be encouraged to buy some cake or cookies as well – “Would you like a pasty with that?” is a common encounter with a smiling barista as they waft the freshly baked chocolate fumes in your direction with a wave of the hand. In a more domestic setting, we often keep the cookie jar beside the coffee jar. This often leads to coffee consumption also being associated with the consumption of refined sugars and unhealthy fats, and so when working out how safe it is then that also is another factor in such associations.

The association sword cuts both directions because people often cut coffee out of their diet as a response to other health issues. That reality just might explain why consuming it crafts an illusion of it being beneficial, and so factoring that into an observational study is very challenging.

So where exactly do things now stand?

What is clear is that study after study does confirm that drinking coffee is generally safe …. but …

  • Coffee and pregnancy don’t go well together – the studies appear to associate a higher risk of lower birth weights with coffee consumption
  • Coffee was also associated with an increased risk of fracture in women

Beyond that, it is not only safe, but it appears to actually be beneficial to your health.

Exactly how beneficial, what does that actually mean?

They determined that lowest risk of illness is associated with about 3-5 cups per day.

Now let’s be clear here, they did not just find that drinking coffee will do you no harm, they found that people who drink moderate amounts appear to have a better health outcome than those who drink none.

drinking three cups of coffee a day was associated with the greatest benefit in terms of cardiovascular disease, coronary heart disease, and stroke, when compared with not drinking coffee.

Consumption at this level was associated with a 19% lower risk of mortality from cardiovascular disease (relative risk 0.81, 95% confidence interval 0.72 to 0.90),

a 16% lower risk of mortality from coronary heart disease (relative risk 0.84, 0.71 to 0.99),

and a 30% lower risk of stroke mortality (0.70, 0.80 to 0.90)

In a word … wow.

Can I now expect to be given a prescription for Coffee?


Now this is where you really do need to rev up your skepticism to full throttle. The word “beneficial” is emotional music to the ears of a coffee drinker such as myself and millions of others.

While it is safe to consume, this is not medicine. An association between coffee consumption and various health benefits has been observed, and that is all we have here. It does not establish a causal relationship, this is just or correlation.

Or as the BMJ puts it …

Should doctors recommend drinking coffee to prevent disease? Should people start drinking coffee for health reasons? The answer to both questions is “no.”

In other words, the key message here is this …

The evidence is so robust and consistent across studies and health outcomes, however, that we can be reassured that drinking coffee is generally safe

but (if I may be permitted to drum it in once again) no causal relationship has been established.

Further Details: The Meta-Analysis

The full Meta-Analysis is available here.

Entitled : Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes.

It’s a long paper, and so here are the results and conclusions …

Results The umbrella review identified 201 meta-analyses of observational research with 67 unique health outcomes and 17 meta-analyses of interventional research with nine unique outcomes. Coffee consumption was more often associated with benefit than harm for a range of health outcomes across exposures including high versus low, any versus none, and one extra cup a day. There was evidence of a non-linear association between consumption and some outcomes, with summary estimates indicating largest relative risk reduction at intakes of three to four cups a day versus none, including all cause mortality (relative risk 0.83, 95% confidence interval 0.83 to 0.88), cardiovascular mortality (0.81, 0.72 to 0.90), and cardiovascular disease (0.85, 0.80 to 0.90). High versus low consumption was associated with an 18% lower risk of incident cancer (0.82, 0.74 to 0.89). Consumption was also associated with a lower risk of several specific cancers and neurological, metabolic, and liver conditions. Harmful associations were largely nullified by adequate adjustment for smoking, except in pregnancy, where high versus low/no consumption was associated with low birth weight (odds ratio 1.31, 95% confidence interval 1.03 to 1.67), preterm birth in the first (1.22, 1.00 to 1.49) and second (1.12, 1.02 to 1.22) trimester, and pregnancy loss (1.46, 1.06 to 1.99). There was also an association between coffee drinking and risk of fracture in women but not in men.

Take note the wiggle vague words I’ve underlined below and remember that this is the alpha source for any and all news articles you might read about this latest news…

Conclusion Coffee consumption seems generally safe within usual levels of intake, with summary estimates indicating largest risk reduction for various health outcomes at three to four cups a day, and more likely to benefit health than harm. Robust randomised controlled trials are needed to understand whether the observed associations are causal. Importantly, outside of pregnancy, existing evidence suggests that coffee could be tested as an intervention without significant risk of causing harm. Women at increased risk of fracture should possibly be excluded.

Bottom Line – Safe yes but not if you are pregnant or concerned about fractures, and beneficial … perhaps.

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