Tag Archives: british medical journal

Butter is good for your heart !!

10 Feb

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This story from last week interested me, as it seemed to contradict all of the health advice we’ve received for years. According to the headline replacing butter with polyunsaturated fat margarine ‘doubles heart risk‘. The story is based on a paper recently published in the British Medical Journal. The first thing that set me thinking was that the study is a reanalysis of missing data from a student conducted with Australian men between 1966 and 1973. Based on this alone it would be interesting to get students to think about whether you could generalise from a sample of Australian men from forty years ago. I may be adopting a dreadful stereotype, but I suspect that the diet of a 1960’s Australian male hugely different from today’s average thus making sensible comparisons rather difficult.

Secondly, the newspaper article is a great example for encouraging students to read all of an article. Towards the end of the article two academics are quoted who clearly don’t think the story has much strength:

Professor Tom Sanders, of King’s College London, said the study was ‘enormously underpowered’, of ‘little relevance to diets today’ and its findings had been refuted by recent better studies.

Professor Brian Ratcliffe, of  Aberdeen University, said: ‘This paper does not provide evidence for changes to the current recommendations for a healthy diet.’

FInally, this story is a lovely example of one of the key points of the rational thinking curriculum/syllabus that I’m trying to assemble. It you read through the reader comments attached to this story you can see the Naturalistic Fallacy at work. Many of the Mail’s readers seem to conclude that it is obvious that butter is more healthy than margarine because butter is ‘natural’ and margarine in ‘manufactured’. A moment’s thought exposes flawed logic of this argument, and yet it is hugely widespread.

It’s of note that the original article is freely available on the BMJ website, and thus for once academic journal paywalls aren’t actively hampering rational thinking !

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Eating chocolate and drinking milk will make you a Nobel Prize winner

22 Jan

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You could hardly miss this story, as it seems to have been all over the media this week. The headline of the  Daily Mail version of the story focused on a correlation between a country’s milk consumption and the number of Nobel Laureates from the country. The story went on to cover a similar correlation between chocolate consumption and Nobel prizes. The same story appeared around the world including Bangladesh, USA (Time), Pakistan and Ghana.

You might just dismiss this story and the usual newspaper rubbish, but when you read through the story it is based on material from the Practical Neurology (A British Medical Journal publication) and from the New England Journal of Medicine. When you look at the Practical Neurology article one can feel the authors tongues firms in their cheeks and in the second line of the article they acknowledge that correlation obviously doesn’t imply correlation.

This story is useful for two different types of teaching. At a basic level it’s a nice way to illustrate the idea that correlation doesn’t imply causation. In discussion with students I’m pretty sure you could come up with a lot of possible variables that might me mediating this relationship. My own mind wanders to the figures for lactose intolerance in Asian countries being 75% plus.

At a much higher level I think there is an interesting discussion to be had about the responsibility of scientists when publishing correlational data. Whilst both the papers that this story was based on were published in peer-reviewed journals (and were thus aimed at an audience who would understand correlation and causation) it’s not unreasonable to suggest that given the subject matter both the authors and the journal editors would be aware that the popular press were likely to pick it up. Under these circumstances my question is ‘Do the authors and editors have any responsibility to consider the wider audience and their lack of understanding and correlation”? It’s all very well for us to bemoan poor science reporting in the popular press, but we ar least partially responsible ?

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