Hi Everyone - also happy to contribute. Here are some thoughts
1) in the Lancet PURE study the appendix does present the individual geographic regions and the results don’t look much different - so that is somewhat useful
2) more importantly the whole nutrition literature is at best VERY tricky
3) there have only ever been 3 RCTs of food looking at clinically important out comes that I am aware o - Lyon diet heart study, WHI low fat and PREDIMED - and they all have issues as well
4) so if anyone is waiting for RCTs to inform nutrition you will be waiting a long time
5) so all we will have is cohorts with all their obvious limitations
6) I think at present all we can say with any confidence (and it isn’t much confidence) is the best way to eat from a population perspective is the Mediterranean type diet in Moderation, and avoid as much as possible highly processed food/trans fats - except when you are in a mood that will only be improved by a Big Mac :) then on occasion go crazy - by they way I’m pescatarian so I go the Egg McMuffin route.
7) the whole animal rights and environmental issues are also very important but that is a whole other topic
If anyone is interested in nutrition and like the song Hotel California I tried to incorporate many of these points into, hopefully, a fun and informative medical musical parody.
https://youtu.be/tfH6qSSTa90
James
> On Nov 24, 2018, at 7:03 AM, David Nunan <[log in to unmask]> wrote:
>
> Hi Rod,
> I'd happily contribute to this.
> Indeed there've been at least three studies from the PURE data set. I envisage if the same/similar issues occur across all three (as well as others [including in the Lancet] that show opposing results)? There's a need for a clarification piece of the strengths and inherent weaknesses of this type of research. Causal diagrams may help illustrate these issues (I imagine colliders are impacting as much as confounders).
>
> It could start with an individual case perspective to illustrate the difficulty in applying epidemiological/trial evidence to individuals, and provide an example of how the totality of all types of evidence need to be put together to create a coherent picture of how the best available evidence can inform decisions in light of the individual's preferences/circumstances.
> Best, David
>
> On 24/11/2018, 02:32, "Evidence based health (EBH) on behalf of Rod Jackson" <[log in to unmask] on behalf of [log in to unmask]> wrote:
>
> Dear all. For a great example of almost certain substantial confounding (not to mention measurement error and cross-over) please critique the latest PURE Study analyses in this week’s Lancet. Why do journals continue to publish papers that could be used in introductory Epidemiology classes as ideal examples of how to introduce confounding into an analysis? The paper is controversial and comes from a well-known clinical trialist who has an international reputation for undertaking high quality randomised controlled trials, a study type designed specifically to minimise confounding. Yet this paper describes an analysis of the association between dairy food consumption and disease in people from countries as diverse as Canada and China and Sweden and Zimbabwe. This mix of a food group that can be expensive and difficult to store without refrigeration, a disease group that is easy and quick to modify and a participant group from extremely diverse populations provides an ideal environment for confounding. I don’t know how it would be possible to confidently control for confounding in the association between dairy food and disease in just one of these populations, let alone across such diverse populations? And using the same adjustment factors in all populations. Who eats dairy products in Canada and Sweden? Are they likely to be similar to those who eat the same foods in China and Zimbabwe or Bangladesh? Higher consumption of total dairy products was associated with lower total mortality, lower non CVD mortality and lower CVD mortality - appeared to be good for everything! Yet, when examining more specific outcomes, there was no protective association observed for the only specific atherosclerotic outcome - myocardial infarction - and the strongest protective association was for stroke - a large proportion of which would be haemorrhagic rather than atherosclerotic, given the large proportion of participants from low and middle income countries.
>
> Does anyone on this list know of a reputable and frequently read journal that would accept a substantial critique of PURE? I have only scraped the surface of the necessary critique. It needs more than a letter to the Lancet editor.
>
> Regards Rod Jackson
> Professor of CVD Epidemiology
> University of Auckland, New Zealand
>
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