“the report is more hypothesis-generating for future research than a rigorous scientific study. Find us some money and we will do a proper job. You can quote me for that.” Professor David Smith (Oxford). Scientific adviser for Food for the Brain.

A great deal has been written about media ‘nutritionist’, Patrick Holford. He’s the chap who thinks that chromium and cinnamon can treat diabetes (watch the video), among other odd beliefs. For all the details, check badscience.net, holfordwatch and here.
For a quick synopsis, look at Holfordmyths.org.

Patrick Holford and Drew Fobbester are joint researchers and authors of the Food for the Brain Child Survey , September 2007 (pdf). Holfordwatch has made a very thorough study of this report, in eight parts (so far). They conclude

“HolfordWatch can not share the optimism for these claimed benefits and finds that there is insufficient data to support them in a robust manner.”

There are many detailed questions, but the basic problem with the report is very simple. The fact that is (a) self-selected and (b) not randomised make it just another naive observational study. The stunningly obvious confounder in this case is, as so often, the socio-economic background of the kids. That was not even assessed, never mind any attempt being made to allow for it.

This isn’t just pedantry because what matters is causality. It is worth very little to know that eating vegetables is correlated with high SAT score if the correlation is a result of having well-off parents. If that were the reason, then forcing kids with poor parents to eat vegetables would make no difference to their SAT score because their parents would still be poor. The only conclusion of the study seems to be that we should eat more fruit and vegetables, something that we are already lectured about in every waking moment.

Many questions about the report have not yet been answered by its authors. But the report has a panel of scientific advisors, some of whom at least seem to be very respectable (though not ‘orthomolecular medicine‘, which is a cult founded on the batty late-life beliefs of the once great Linus Pauling that Vitamin C is a magic bullet).

Furthermore they are thanked thus

As it happens, David Smith is an old friend, so I wrote to him, and also to Philip Cowen, with some detailed questions. I didn’t get detailed answers, but the responses were none the less interesting. Cowen said

“I did see the report and quite agree with your conclusions that it an observational study and therefore not informative about causality.”

“The advice about diet seems reasonable although, as you point out, probably somewhat redundant.”

But still more interesting, David Smith told me (my emphasis)

“the survey was the largest of its kind and was done on minimal funding; hence several matters could not be dealt with and so the report is more hypothesis-generating for future research than a rigorous scientific study. Find us some money and we will do a proper job. You can quote me for that, if you wish.”

I’d grateful to David for his permission to quote this comment, It seems that Holford’s top scientific advisor agrees that it is not a rigorous study, and even agrees that the “proper job” is still to be done.

But it does seem a shame that that was not made clear in the report itself.