It was 23rd February 2017 and I was over in Breckenridge when friends started to send me links to media reports about 10-a-day. I switched on my phone and the in-box was full of radio/newspaper interview requests to talk about 10-a-day (most of them had already passed, as we were 7 hours behind).
This BBC article was typical of the reporting. No questioning, no critical evaluation – just acceptance of the new myth of 10-a-day, just as the myth of 5-a-day has barely been questioned and just as a new myth of 7-a-day tried to gain acceptance on April Fool’s Day 2014 (ho ho).
The study was an outstanding undertaking – don’t get me wrong. It was almost the pups nuts as far as research goes. I say “almost” because the pups nuts is a systematic review and meta-analysis of randomised controlled trials (RCTs) and this was a systematic review and meta-analysis of prospective cohort studies. The latter are the ones where populations are studied for long periods of time – diet and lifestyle data are collected at the start and then the participants are observed to see which conditions they go on to develop, so that we can spot associations between, say, smoking and lung cancer. And that’s all we can observe – associations – we cannot make any inference about causation without thorough examination of the Bradford Hill criteria and then, ideally, an actual RCT (large enough and long enough) to test any observed associations.