Harcombe Z, Baker JS, Cooper SM, Davies B, Sculthorpe N, DiNicolantonio JJ, et al. Evidence from randomised controlled trials did not support the introduction of dietary fat guidelines in 1977 and 1983: a systematic review and meta-analysis. Open Hear [Internet]. 2015 Feb 9;2(1).
This paper is the first in a series of four, looking at four questions, by lead author Zoë Harcombe, PhD (@ZoeHarcombe), whose work I have been following on social media and via postings on this blog – all of it interesting to me.
- The first review examined RCT evidence available to the dietary guideline committees in 1977 and 1983.
- The second review examined epidemiological evidence available to the dietary guideline committees.
- The third review examined RCT evidence available today, to see if extant dietary guidelines have been proven in retrospect.
- The fourth review examined epidemiological evidence available today, to see if extant dietary guidelines have been proven in retrospect.
The recommendations we’re talking about are these, adopted by the United States in 1977 and the UK in 1983:
The dietary recommendations in both cases focused on reducing dietary fat intake; specifically to (1) reduce overall fat consumption to 30% of total energy intake and (2) reduce saturated fat consumption to 10% of total energy intake.
What’s the evidence?
There wasn’t convincing evidence available regarding fat intake reduction when the guidelines were introduced.
From the literature available, it is clear that at the time dietary advice was introduced, 2467 men had been observed in RCTs. No women had been studied; no primary prevention study had been undertaken; no RCT had tested the dietary fat recommendations; no RCT concluded that dietary guidelines should be introduced.
An exchange between Dr Robert Olson of St Louis University and Senator George McGovern, chair of the Dietary Committee, was recorded in July 1977. Olson said “I pleaded in my report and will plead again orally here for more research on the problem before we make announce- ments to the American public.” McGovern replied “Senators don’t have the luxury that the research scientist does of waiting until every last shred of evidence is in”.
And the only way to interpret this literature is to use the responses and social media
Unlike almost any other topic in medicine/health I have encountered, it is clear that it’s not enough to read the journal article – you have to read the responses to the journal article, the declared interest statements, and then go to social media to critically analyze the analysis.
The responses to the paper inquire about evidence that was available after the guidelines were introduced, which is covered in papers 2,3,4 that I’m reviewing.
Regardless, it’s worth noting that the responses do not dispute that there wasn’t convincing evidence available when nutritional guidelines for 220 million Americans and 56 million UK citizens were created.
And as I have stated previously, I am very happy that the people doing work in this area are engaged in social media where they are accessible and can answer questions. Again, like almost any other topic in medicine/health, I haven’t seen this level of engagement and it’s a great exemplar for all things health. (see: Just Read: Does Hyperinsulinemia cause obesity, and academic discourse on Twitter (finally))