On Monday, several national newspapers, including the Mail and the Express, reported that “just one glass of cherry juice a day can slow down the ageing process – and may even save your life”.
“A tumbler of 250ml of diluted juice,” we were told, “offers better protection against cancer, heart disease and stroke than more than 20 typical portions of fruit and vegetables,”
This claim was backed up nutritionists including Patrick Holford – who’s credibility has been the subject of repeated attacks from Ben Goldacre and his Bad Science pals – and who, a year ago, the Advertising Standards Authority found to be making claims that were ‘likely to mislead’ in leaflet he was sending out.
You’d have thought that, in making claims that drinking cherry juice prevented ageing, the science in question would have measured the effects of cherry juice on how people age. But it didn’t.
Next best bet would probably be to study the effect of cherry juice on animals, or human cells, or cancer cells, or some other sort of ‘model’ system. But it didn’t do this either.
So what did it do then? The study, which is published in Nutrition Practicer measured the amount of “antioxidants” in the cherry juice, compared to other fruit.
Why isn’t this convincing?
Here at Cancer Research UK we are extremely sceptical that cherry juice holds the secret of a longer, healthier life.
Although there’s emerging evidence that some antioxidants may play some role in in preventing some people from some types of disease, it is very much overstating the case to say that, because a food contains ‘a lot’ of antioxidants it must therefore protect against all disease.
It’s exactly the kind of logical fallacy that Ed blogged about back in July.
But what else did the story say?
After making these grand, unsubstantiated claims, the story then went on to tell us that there was no point in eating cherries to get that massive antioxidant boost – cherries bought in the UK are a different variety.
But never fear! Because the story also informed us that a new product was available on the supermarket shelves – a juice made from the exact variety of cherry that the scientists happened to study.
Now fancy that.
Simon K October 1, 2008
I saw Ben Goldacre talking at the South Bank the other day discussing exactly this issue – the over-interpretation of perfectly valid scientific experiments. It may be perfectly good science to say, “this variety of juice contains lots of antioxidants” – the fallacy comes with the next step, which therefore assumes it’ll make you live longer.
More generally, this sounds like another salvo in what Goldacre memorably described as “the Daily Mail’s sisyphean task to divide all inanimate objects in the world into those which cause, and those which cure, cancer”.