Ann Walker festival: "There is no convincing evidence that Ginkgo biloba is efficacious for dementia and cognitive impairment"

1A slight interruption to your usual service here, while Holford Watch participates in the Ann Walker blog festival. To cut a long story short, UCL was “recently contacted by Dr Alan Lakin on behalf of his wife, herbal medicine practitioner Dr Ann Walker, in relation to comments made about her, on a websitehosted by UCL, by Professor Colquhoun, a distinguished UCL pharmacologist”. In response to Lakin’s contact, UCL forced Colquhoun to move his excellent blog temporarily, though after legal advice was taken I’m pleased to say it should be reinstated at UCL pretty soon.

However, this shouldn’t be the end of the affair. As Ben Goldacre puts it:

There is a more serious issue in the background, however. It strikes me that there is a sizeable cohort of people who sell themselves and their wares by making scientific claims, but then use bullying and legal threats when their claims and ideas are criticised. This to me is completely unacceptable. I suspect that in the case of Dr Lakin and Dr Walker their efforts in this case may backfire, and a great deal more attention will now fall on their work…Are we about to see a festival of Ann Walker?

I certainly hope that we’re going to see a festival of Ann Walker – to defend the freedom of bloggers to write and to criticise. Already, the excellent Science Punk and Quackometer blogs have began to look at Walker’s work. My own modest contribution is below – hopefully, many more will follow. If you’re contributing to the festival, let me know (you can e-mail me through my blogger profile) and I’ll add a link to you here.

Writing on HealthSpan’s site (where ginkgo biloba pills are sold) Ann Walker argues that

More evidence exists for the beneficial effect of ginkgo on mental function than for any herb for any body condition. Indeed, ginkgo is the most well-established herbal treatment for Alzheimer’s disease….The number of double-blind, placebo-controlled human studies on the effects of ginkgo on mental health now exceed 50. The authors of the influential Cochrane review (2002), while calling for further studies, added: ‘Overall there is promising evidence of improvement in cognition and function associated with it’.

These are bold claims. Holford, similarly, argues that ginkgo is a “proven brain booster…A review of all the studies up to 2002 concluded that there is ‘promising evidence of improvement in cognition and function with ginkgo'”*. Unfortunately, their interpretation of the evidence is somewhat selective.

Walker has, on occasion, spoken for HSIS (an “educational” body funded by The Boots Company PLC, Bayer PLC, Perrigo, Seven Seas Ltd and Wyeth Consumer Healthcare), and been very critical of some studies that have argued against the benefits of supplement pills. For example, responding to a high quality JAMA meta-analysis of antioxidant supplements (which found that some actually increase mortality) Walker argues that “The results of these mixed-sample metaanalyses are worthless”. Clearly, then, one would expect Walker to demand a high standard of evidence before recommending any pills.

As noted above, Walker and Holford both sing the praises of Gingko, quoting part of the conclusion of a Cochrane meta-analysis to do so. However, it’s worth quoting the conclusion of this meta-analysis at more length, to get a fuller picture of the evidence:

Many of the early trials used unsatisfactory methods, were small, and we cannot exclude publication bias. Overall there is promising evidence of improvement in cognition and function associated with Ginkgo. However, the three more modern trials show inconsistent results. Our view is that there is need for a large trial using modern methodology and permitting an intention-to-treat analysis to provide robust estimates of the size and mechanism of any treatment effects.

This sounds a lot less positive than Holford’s and Walker’s summary of the review. In effect, this review concludes that – while further trials would be useful – the current evidence base for the use of ginkgo to treat cognitive decline is poor. Therefore, Walker not only uses a meta-analysis here (having been so critical of the JAMA meta-analysis) but Holford and Walker’s interpretation of the meta-analysis is very problematic.

To make matters worse, a February 2007 Cochrane Review of the evidence re. ginkgo and cognitive impairment found that

There is no convincing evidence that Ginkgo biloba is efficacious for dementia and cognitive impairment. Many of the early trials used unsatisfactory methods, were small, and publication bias cannot be excluded. Overall, evidence that Ginkgo has predictable and clinically significant benefit for people with dementia or cognitive impairment is inconsistent and unconvincing. Two of the best most recent trials, which are also among the largest trials, found no difference between placebo and Ginkgo.

To be blunt, it looks like the trials on ginkgo that Walker so welcomed have been useful – and showed that it doesn’t help with cognitive impairment. The above quotes from Walker come from a 2004 article. However, given Walker’s obvious concern with the way that scientific articles – such as the JAMA review of antioxidant supplements – can mislead the public, it’s a shame that she hasn’t managed update her HealthSpan article in the light of the new evidence (Walker has posted two new articles February 2007).

Likewise, Holford’s book may have been in press before the newer Cochrane review came out. However, one would hope that future editions will be revised to take this into account. Moreover, given that Holford is keen that people do not waste money on supplements, one would hope that he will add an appropriate warning to the ginkgo pills sold by Health Products for Life – to make sure that customers don’t waste money by buying this as a treatment for cognitive decline.

*New Optimum Nutrition for the Mind (Piatkus, 2007 Edition), p395.



Filed under Alan Lakin, Ann Walker, blogging, David Colquhoun, ginkgo, health products for life, patrick holford, UCL

3 responses to “Ann Walker festival: "There is no convincing evidence that Ginkgo biloba is efficacious for dementia and cognitive impairment"

  1. woodchoper

    Its also worth noting that on 16 June 2008 the BBC reported that:

    “A herbal extract used by an estimated 10% of people with dementia is not an effective treatment for it, an Imperial College London study suggests.”

    “But a six-month trial of 176 people with mild to moderate dementia found no difference between those taking ginkgo biloba and those taking placebo.

    The results are in the International Journal of Geriatric Psychiatry.”

  2. Thanks for the update. Given the popularity of Ginko (I’ve read that up to 10% of people with cognitive decline use it) it would have been exciting and useful had it had any useful degree of efficacy. It is in-line with the Cochrane review that it didn’t.
    However, let’s not hold our breath waiting for Holford to issue an update, eh?
    McCarney R, Fisher P, Iliffe S, van Haselen R, Griffin M, van der Meulen J, Warner J. Ginkgo biloba for mild to moderate dementia in a community setting: a pragmatic, randomised, parallel-group, double-blind, placebo-controlled trial. Int J Geriatr Psychiatry. 2008 Jun 9.

  3. Yes – thanks for the update. It will be interesting to see whether sites such as Healthspan update their articles on Ginkgo…though I also won’t be holding my breath.

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