It feels like crystal

Ben Goldacre
Thursday December 11, 2003
The Guardian

· As a Guardian-reading science bunny, there’s something slightly galling about the way that right-on beliefs so often seem to cluster together. For example, what’s the connection between torturing political dissidents and crystal magic? Over to the Amnesty Christmas catalogue, and its magnificent Salt Crystal Lamp. “Crystals are one of nature’s most effective purifying minerals. They cleanse the air by absorbing humidity. The process releases negative ions which neutralise positively charged particles of air pollution, creating the fresh air found by the sea or in the mountains.”

· Is Amnesty doing this to give us some small window of experience into what it’s like to be persecuted for your beliefs? Crystals do not absorb water, or at least, if salt crystals did, they would dissolve away pretty quickly, and you’d be left wondering which puddle to stick in the post to demand your money back with. Nor do they work as air fresheners. And you don’t need to spend £34.95 to find that out for yourself.

· And now to Michael van Straten, the Daily Express’s “nutritionist”. “Recent research,” he says, has shown that turmeric is “highly protective against many forms of cancer, especially of the prostate”. Every single day of every single week, you can be sure that a pseudoscientist somewhere is extra- polating merrily away from obscure lab findings to pretend that something is proven and effective. Ridiculous. There are, for turmeric and prostate cancer, speculative lab studies of cells growing or not growing under microscopes, and usually from rats. That’s not enough. Forty years ago this guy called Bradford-Hill knocked out a set of criteria for assessing causality. Read them once: it will only take 20 seconds of your life, and it is the cornerstone of evidence-based medicine, after all, which is what these guys are always pretending to call on. It needs to be a strong association, which is consistent and specific to the thing you are studying, with a temporal association between cause and effect; ideally there should be a biological gradient, such as a dose-response effect; it should be consistent, or at least not completely at odds with, what is already known (because extraordinary claims require extraordinary evidence); and it should be biologically plausible. The Daily Express’s nutritionist has got biological plausibility, and nothing else. Well, that and 20 seconds’ reading to change the habit of a lifetime.