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There's a great New Yorker cartoon - two cavemen, sitting in a cave, looking suitably homo habilis or something, all sloping foreheads and protruding jaw. The caption reads:
'Something's just not right - our air is clean, our water is pure, we all get plenty of exercise, everything we eat is organic and free-range, and yet nobody lives past thirty.'
I think of it whenever someone trots out a living-close-to-the-soil, modern-lives-are-killing-us mantra about how we should stop eating cooked food or only wear natural fibres or whatever. Humans live longer, healthier lives now than wethey have at any other point in history (and that's largely true wherever you live in the world), so if living like our ancestors is so great, how come they all died of diseases we don't even have names for anymore?
The 'Paleo' diet was recently back in the news, this time because a study found that people who followed it were less likely to die of bowel cancer.
The 'Paleo' diet, if you're wondering, does pretty much what it says on the tin: you can't eat anything that our hunter-gatherer ancestors didn't eat. So, no preserved or processed food, no bread, no pasta; no booze or coffee; lots of berries and green leaves. If that was as far as it went, sort-of fair enough, since there's fairly good evidence that heavily processed foods, especially the stuff with loads of added salt and sugar and so on, isn't very good for you. We know that eating lots of fruit and veg is good for you.
But our hunter-gatherer ancestors not only hadn't got industrialised abbatoirs and so on, they also hadn't invented agriculture. That's why they were hunter-gatherers. So, if you're taking the Paleo diet seriously, no cultivated grain, even though they're full of health-giving protein and fibre. No dairy, even though it's full of calcium.
'But that's how we evolved!' you might think. Well, yes, that's how some of our ancestors lived, for a period of our evolution. But since then, we've evolved - for instance, a large swath of humanity is now lactose-tolerant in adulthood, an evolutionary response to our domestication of cattle.
That's all by the by, though. You might reasonably say, who cares how we evolved, as long as the Paleo diet helps reduce cancer. And it does, right?
Well, possibly, sort of. I can't get hold of the actual study, but from the Mail's report it involved following 2,000 people and grading them on how 'Paleolithic' (and separately how 'Mediterranean'); measuring the number of cases of colorectal adenoma among them - colorectal adenoma being a precursor to bowel cancer. There were fewer cases among those on the more Paleo diets: 29 per cent fewer for women and 51 per cent fewer for men.
If that's all there is to the study, then this tells us nothing new at all: people who eat fancy diets are almost certainly likely to look after themselves in other ways, and are probably richer and better educated as well, so they're much less likely to get cancer anyway.
None the less, probably, putting yourself on something called the 'Paleo diet' probably is good for you, if it involves eating lots of fruit and veg and not eating too much bacon. Because the only really good evidence we have for any sort of diet is: you should eat a mixed one, with plenty of fruit and veg and not too much processed meat.
We know all this stuff already and it has nothing to do with reclaiming our Edenic hunter-gather paradise. If telling yourself that you're living the caveman lifestyle helps you stick to it, then help yourself. But as far as I'm concerned it just makes you look like an idiot.