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Dietary fat guidelines: a storm in a teacup! - Francesco Cappuccio

Franco CappuccioFrancesco Cappuccio, a Professor of Cardiovascular Medicine & Epidemiology at the Warwick Medical School, said: “The article by Harcombe et al published in Open Heart Journal today (10 February) [1] is a storm in a teacup.

“The authors raise an interesting point in trying to assess the evidence from RCTs supporting a beneficial effect of reducing dietary fat intake for the prevention of cardiovascular endpoints at the time when US and UK guidelines made public health recommendations to the general public to reduce fat intake alongside other measures now considered the pillars of non-communicable disease prevention globally.

“In doing so, they embroil themselves in an awkward and spurious pseud-scientific exercise to extrapolate results from 1970s and 1980s to current practices. They include a very few studies carried out at the time, all different from each other (primary and secondary prevention, different fat substitutions, different control diets etc), most of which of little statistical power (compared to modern trials) and unable to detect small differences in outcomes, even when included in a meta-analysis.

"Since then, the body of RCTs have mushroomed and the collective evidence does not seem to have reverted the principles applied 40 years ago [2-4].

“At any stage of scientific knowledge decisions – and particularly those regarding public health – are taken on the basis of the best available evidence which would include – but not be limited to – that coming from randomized clinical trials. John Snow actions during the cholera epidemic of the mid-1800 in London and the quoted response of Senator McGovern in 1977 reflect this spirit.

“If this principle had not been followed, we would not have had policies banning tobacco smoking, fighting obesity, discouraging physical inactivity, controlling excessive alcohol intake, promoting a population reduction in salt intake, encouraging the consumption of more fruit and vegetables. Perhaps some of these authors would argue against these policies too.

“Long-term clinical trials of dietary changes on long term outcomes are difficult and often impossible to carry out. Furthermore recommendations include changes in diet rather than specific nutrients. Evaluation and modelling studies of the impact of policy changes have clearly demonstrated that a reduction of fat intake and ensuing cholesterol reductions – alongside reductions in blood pressure and smoking rate and despite increasing body weight and physical inactivity - provide a significant contribution and explain more than half of the secular reductions in coronary heart disease and cardiovascular disease observed in the US and the UK [5-6].

“Whilst we should continue searching for improved evidence we should continue to endorse current recommendations as firmly asserted by the UN High level group on non-communicable disease prevention aiming at a 25% global reduction in cardiovascular disease by 2025.”

References:

1. Harcombe Z 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 Heart 2015; 2:e000196

2. Bucher CH et al. N-3 Polyunsaturated Fatty Acids in Coronary Heart Disease: A Meta-analysis of Randomized Controlled Trials. Am J Med 2002; 112:298 –304.

3. Mozaffarian D et al. Effects on Coronary Heart Disease of Increasing Polyunsaturated Fat in Place of Saturated Fat: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. PLoS Medicine 2010; 7 (3): e1000252

4. Hooper L et al. Reduced or modified dietary fat for preventing cardiovascular disease. Cochrane Database Syst Rev. 2011; (7): CD002137

5. Ford ES et al. Explaining the decrease in US deaths from coronary disease, 1980-2000. N Engl J Med 2007;356:2388-2398

6. Unal B et al. Modelling The Decline In Coronary Heart Disease Deaths In England And Wales, 1981-2000: Comparing contributions from primary prevention and secondary prevention. BMJ 2005;331:614-615.

Note to Editors:

Issued by Lee Page, Communications Manager, Press and Policy Office, The University of Warwick. Tel: +44 (0)2476 574 255, Mob: +44 (0)7920 531 221. Email: l.page@warwick.ac.uk.


 

Contact:

Lee Page, Communications Manager

+44 (0)2476 574 255

+44 (0)7920 531 221

l.page@warwick.ac.uk