Showing posts with label chocolate. Show all posts
Showing posts with label chocolate. Show all posts

Friday, 11 September 2015

The rationalist spa: an unmet need

I’ve had a few spa experiences, though I’m hardly a connoisseur. I've found  a spa is a good place to chill out and gossip with friends, and on the rare occasions when I stay at a fancy hotel, I’ve come to enjoy the process of whiling away the period between lunch and cocktails in a hot bubbly tub.

At the same time, I’ve become fascinated by the language used to advertise the available activities. I suspect most people who go to a spa don’t have any specific ailments, but they want to come away feeling more relaxed and vibrant, and the talk of 'therapies' and 'treatments' manages to create the comforting illusion that health can be shifted from suboptimal to optimal by various potions and practices. Particularly intriguing is the focus on foodstuffs. In a spa, you don’t ingest food: you rub it on the skin, sniff it, or slather yourself with it. I’ve always suspected there is an element of sublimation in this: most women who wish to remain slender have to suppress the desire to eat delicious things, and the spa provides an opportunity to interact with food without getting fat.
In the hotel I’ve been staying in you could be massaged with essential oils of grapefruit, have mango butter rubbed on your feet or head, be scrubbed with papaya and mandarin, or have your muscles relaxed by a concoction of rice and milk. Rather disappointingly, they didn't offer the ultimate decadence: a ‘chocolate wrap’, where you start with a warm milk soak, then get scrubbed with vanilla and bran, before being enveloped in a warm cocoa butter ‘masque’ (a word that always reminds me of Edgar Allan Poe's scary story).
It’s clear that there’s a lucrative market for this kind of thing. Many of us feel stressed by modern life, and if being smothered in chocolate or fruit makes us feel relaxed, why not?
Alas, though, for me the sense of relaxation is counteracted by irritation with the garbage that you have to endure while undergoing something as basic as a pedicure. Some of it is just overblown advertising guff, e.g. “Drawing on the elemental wisdom of nature, our treatments both invoke and restore the body’s natural equilibrium”. What does this even mean? The images are of blockage and decay being removed: “Clearing stagnant energy is the focus of the Spring Clean Scrub”. But the worst examples are those with medical overtones, with talk of healing, detoxification, and wellness. We are told that: “This wrap is highly effective in purging toxins and boosting the blood and lymphatic circulation” or "The polyphenols in cocoa delay the ageing process, causing you to look younger". Or even “The body is generously encased within a cooling serum”. Cripes! If you look up serum in a dictionary, this is a seriously scary idea.
I have, of course, always just gone with the flow. Attempting to debate the scientific basis of aromatherapy or ayurveda with a practitioner who makes their living administering these treatments is unlikely to make either of us more relaxed or vibrant. But I do wish someone would open a spa for rationalists, where one could go and get a good massage or get encased in mud just for the fun of it, without a lot of guff about energy blockages and deep-seated toxins.

Tuesday, 13 November 2012

Flaky chocolate and the New England Journal of Medicine



Early in October a weird story hit the media: a nation’s chocolate consumption is predictive of its number of Nobel prize-winners, after correcting for population size. This is the kind of kooky statistic that journalists  love, and the story made a splash. But was it serious? Most academics initially assumed not. The source of the story was the New England Journal of Medicine, an august publication with stringent standards, which triages a high proportion of submissions that don’t get sent out for review. (And don't try asking for an explanation of why you’ve been triaged). It seemed unlikely that a journal with such exacting standards would give space to a lightweight piece on chocolate. So the first thought was that the piece had been published to make a point about the dangers of assuming causation from correlation, or the inaccuracies that can result when a geographical region is used as the unit of analysis. But reading the article more carefully gave one pause. It did have a somewhat jocular tone. Yet if this was intended as a cautionary tale, we might have expected it to be accompanied by some serious discussion of the methodological and interpretive problems with this kind of analysis. Instead, beneficial effects of dietary flavanols was presented as the most plausible explanation of the findings.

The author, cardiologist Franz Messerli, did discuss the possibility of a non-causal explanation for the findings, only to dismiss it. He stated “as to a third hypothesis, it is difficult to identify a plausible common denominator that could possibly drive both chocolate consumption and the number of Nobel laureates over many years. Differences in socioeconomic status from country to country and geographic and climatic factors may play some role, but they fall short of fully explaining the close correlation observed.” And how do we know “they fall short?” Well, because the author, Dr Messerli, says so.

As is often the case, the blogosphere did a better job of critiquing the paper than the journal editors and reviewers (see, for instance, here and here). The failure to consider seriously the role of a third explanatory variable was widely commented on, but, as far as I am aware, nobody actually did the analysis that Messerli should have done. I therefore thought I'd give it a go. Messerli explained where he’d got his data from – a chocolatier’s website and Wikipedia – so it was fairly straightforward to reproduce them (with some minor differences due to missing data from one chocolate website that's gone offline). Wikipedia helpfully also provided data on gross domestic product (GDP) per head for different nations, and it was easy to find another site with data on proportion of GDP spend on education (except China, which has figures here). So I re-ran the analysis, computing the partial correlation between chocolate consumption and Nobel prizes after adjusting for spend per head on education. When education spend was partialled out, the correlation dropped from .73 to .41, just falling short of statistical significance.

Since Nobel laureates typically are awarded their prizes only after a long period of achievement, a more convincing test of the association would be based on data on both chocolate consumption and education spend from a few decades ago. I’ve got better things to do than to dig out the figures, but I suggest that Dr Messerli might find this a useful exercise.

Another point to note is that the mechanism proposed by Dr Messerli involves an impact of improved cardiovascular fitness on cognitive function. The number of Nobel laureates is not the measure one would pick if setting out to test this hypothesis. The topic of national differences in ability is a contentious and murky one, but it seemed worth looking at such data as are available on the web to see what the chocolate association looks like when a more direct measure is used. For the same 22 countries, the correlation between chocolate consumption and estimated average cognitive ability is nonsignificant at .24, falling to .13 when education spend is partialled out.

I did write a letter to the New England Journal of Medicine reporting the first of my analyses (all there was room for: they allow you 175 words), but, as expected, they weren't interested. "I am sorry that we will not be able to print your recent letter to the editor regarding the Messerli article of 18-Oct-2012." they wrote. "The space available for correspondence is very limited, and we must use our judgment to present a representative selection of the material received."

It took me all of 45 minutes to extract the data and run these analyses. So why didn’t Dr Messerli do this? And why did the NEJM editor allow him to get away with asserting that third variables “fall short” when it’s so easy to check it out? Could it be that in our celebrity-obsessed world, the journal editors think that there’s no such thing as bad publicity?

Messerli, F. (2012). Chocolate Consumption, Cognitive Function, and Nobel Laureates New England Journal of Medicine, 367 (16), 1562-1564 DOI: 10.1056/NEJMon1211064