Patrick Holford is Head of Science and Education at Biocare and a busy man. However, he has a little time on his hands since becoming a former Visiting Professor at the University of Teesside so he started a blog on which only paying-subscribers were allowed to comment. Sadly, despite the additional writing practice, Holford’s ability to provide accurate references or even link to the correct paper has not improved. We also have a splendid example of flip-flopping on the value of meta-analyses that is nicely captured in a recent Will Wilkinson summary of David Brooks:
Scientists have discovered X. Mostly X vanquishes my intellectual bugbears and confirms me in my prejudices. To the extent it doesn’t, science isn’t really an authoritative source of wisdom, now is it?
We have an interesting instance of this cognitive dissonance in Vitamins Relieve Asthma (this being Holford, you have to go to the main page and look for the April 16 entry to read the 1st paragraph of the post because it disappears when you link to the full article – Vitamins Relieve Asthma). The opening paragraph reads:
Today’s study showing a strong association between lack of vitamin C and A and asthma is consistent with an emerging view that asthma, and other inflammatory diseases, are a result of a number of diet-related factors including lack of antioxidants, omega 3 fats in oily fish and an increase in high allergen foods such as wheat, milk and yeast.
This would be unexceptional were it not that the Dietary antioxidants and asthma in adults study to which Patrick Holford links is not the subject of the news item and the study isn’t readily available as yet.
The excellent Behind the Headlines service provides a considerably more nuanced version of the story and carries an indirect link to the paper for now: Vitamins linked to asthma risk? Their conclusion is:
There are a number of reasons – highlighted by the researchers – why the epidemiological evidence for the association between vitamin intake and asthma and wheeze risk is weak. There are therefore many caveats associated with interpreting the evidence from the available observational studies.
Importantly, the observational evidence on vitamin C varies from the experimental evidence from randomised trials, which was assessed in the recent Cochrane review. This systematic review looked at 330 participants across nine studies, finding no appreciable effect of vitamin C supplementation on asthma risk. Given these inconsistencies, the most important conclusions in this paper are that observational studies are useful for identifying an association, as they have done here, but that they cannot establish causation. The researchers say that it is “now important to carry out larger-scale studies to clarify the link and to see if there is a direct cause between vitamin intake and asthma”.
However, it seems that Holford isn’t really interested in the possible association of dietary vitamins and asthma because he abandons the ostensible topic to assert his own (unevidenced) claims about dietary factors that “decrease inflammation”:
most notable turmeric, ginger, and red onions, rich in quercitin. These kind of foods are also naturally high in antioxidants, including vitamin A and C, which are also anti-inflammatory.
Now, it would be good if Holford genuinely meant food but he usually means supplements and the influence and interactions of these is not necessarily straightforward, as many meta-analyses indicate (summarised by NYT) and even recent bench studies: Interactions of beta-carotene and flavonoids on the secretion of pro-inflammatory mediators in an in vitro system.
Our results urge consideration of the safety of beta-carotene supplementation concerning effects on inflammation and suggest that the interaction between beta-carotene and quercetin or naringenin may alter the effects of beta-carotene on the secretion of pro-inflammatory mediators.
As for this claim by Holford about his much-recommended YorkTest, we can only reiterate that there has never been a published trial or even case series of IgG-diagnosed food intolerance and people with asthma (we summarise York Test, Holford and the literature).
When your body switches into a state of inflammation, which is much like going on red alert, the gut-related immune system is much more likely to attack foods as if they were foes. This results in more anti-food antibodies. These IgG antibodies become specifically targetted against foods. The most common target foods are milk and wheat, high in a protein called gliadin. Yeast and egg reactions are also quite common. A pinprick home test can determine such food allergens and, if these foods are avoided, and a high anti-inflammatory diet, plus appropriate supplements, is followed most asthma sufferers experience considerable relief.
There is no reference for Holford’s superficial statement that a state of inflammation (localised, constrained to the upper or lower respiratory tract, systemic?) is associated with a greater number of adverse reactions to food.
The Advertising Standards Agency is aware of some irritating inconsistencies about its regulatory remit but there may soon be some useful amendments to current loopholes.
For example, Tesco could say something on their website [that breaches the CAP Code] and we can’t do anything about that, but the same statement on a billboard is within our remit.
Interestingly, even now, without any evidence to support those assertions, it would not be appropriate for either Holford or YorkTest to make those claims about the efficacy of York Test or asthma in an advertisement without falling foul of the ASA. However, it is entirely fine to make those same statements on a website as those are not covered by the ASA – we hope that is clear. Similarly, book editors of non-fiction have no obligation to fact-check any advice or facts which is why authors have no obligation to ensure that their interpretation or assertions are correct.
In summary, Patrick Holford’s recommendations on the topic of asthma are fine as long as the reader recalls that there is no current legal requirement that they should be accurate, and as long as they are not repeated in a form that is governed by a regulatory body. There is no possible area of confusion. Move along.