February 16, 2014

Yoghurt health nostalgia

Some of you may be enough older than me to remember yoghurt as the miracle food of the 1970s. It seems to be back. From the Independent, this time, a Herald headline “Low fat yoghurt could combat type 2 diabetes”.

The research paper is open-access, at least for now, so I looked at it.  The first thing to note is that the research did not anywhere distinguish low-fat yoghurt from full-fat. All yoghurt was grouped together in all the analyses.

While the study could not prove a conclusive causal link between eating dairy and lower diabetes risk, the association was strong.

Not all that strong. Comparing high to low yoghurt consumption they only saw a 28% lower risk; the difference in risk was less when they included other “low-fat” fermented dairy products, and the evidence wasn’t all that overwhelming even before you take into account that they looked at 9 different subsets of dairy foods.

The researchers also note that when they compared people who had similar diets except that one group had one more snack (crisps, etc) and the other had one more yoghurt, the risk was 47% lower for the less-crisps group. As they say “suggesting that some of the association may be attributed to not consuming unhealthy alternatives,” and I’d say “some of” could easily mean “all of.”

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Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »