"Coffee's good for you anyway"

You may have read that coffee is good for you, and you're right to bring it up, because a book that ignored it would be dishonest.

Robin Poole and colleagues at Southampton pulled together, in 2017, two hundred and one meta-analyses of observational studies of coffee and health, covering sixty-seven outcomes, along with seventeen meta-analyses of trials. Coffee drinking was more often associated with benefit than harm. The largest reductions in risk, for outcomes including death from any cause and heart disease, were at three to four cups a day compared with none. Higher consumption went with lower rates of several cancers and of liver, metabolic and neurological conditions. Most of the harmful associations disappeared once smoking was properly accounted for. The exceptions were in pregnancy, where higher intake went with low birth weight, preterm birth and pregnancy loss, and a link with fracture in women. The authors concluded that coffee seems generally safe at usual levels and more likely to benefit health than harm, while pointing out that these are associations and that trials are needed to know whether coffee causes the benefits.

The European Food Safety Authority, reviewing the safety of caffeine itself in 2015, put the amount that raises no safety concern for healthy adults at up to four hundred milligrams a day, with no more than two hundred in a single dose, and two hundred a day in pregnancy. For children and teenagers they found the evidence insufficient to set a figure.

So I'll say plainly what this book is not. It's not a case against coffee. If you like it and you're not pregnant, three or four cups a day is well within what the evidence calls safe and may well be doing you some good. Nothing here asks you to stop.

What the book is about is the pattern, and none of the research above is about the pattern. Poole's studies asked how many cups people drank, not when, or why, or what their nights were like. A person who has three coffees before ten in the morning and a person who has one at seven, one at three and one at half past five have the same count and very different days. The first wakes at the level after a proper night. The second lives in a cycle of shortfall, pick-up and a shallow night. The health associations may be identical. The experience isn't.

So keep coffee, if you like it. The argument is about using it as a prop for tiredness that it's helping to cause, and about where in the day it goes. The evidence that coffee is fine is also evidence that you can drink it for pleasure, at a good hour, without guilt, and that's the position the rest of the book is aiming for.