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The healthiness and sustainability of national and global food based dietary guidelines: modelling study

BMJ 2020; 370 doi: https://doi.org/10.1136/bmj.m2322 (Published 15 July 2020) Cite this as: BMJ 2020;370:m2322

Linked Editorial

The healthiness and sustainability of food based dietary guidelines

Linked Opinion

Why food based dietary guidelines need to be more sustainable

Rapid Response:

More data emerges on the global need for plant-based food systems

Dear Editor

The analysis by Springmann et al. (BMJ 2020;370:m2322) is a timely warning to raise awareness on the significant reductions in anthropogenic land use, greenhouse gas emission, and premature mortality that would be associated with an increased use of plant-based dietary patterns. The disparity between the impact potential of national food based dietary guidelines (FBDGs) and the EAT-Lancet recommendations highlights the major role that plant-based food systems could play in our effort to achieve global sustainability and highlights the importance of developing novel methods to overcome the implementation barriers of such food systems.

A major limitation of the study, however, is the exclusion of sodium intake from the assessment of the health impacts of FBDGs. The GBD 2017 Diet Collaborators analysis indicates that the three major dietary causes of death and disability are high sodium intake (3m deaths and 70m DALYs), low whole grains intake (3m deaths and 82m DALYs) and low fruit intake (2m deaths and 65m DALYs)(1). Many of the national FBDGs include sodium reduction, meaning their health benefits will have been underestimated. Conversely, some predominantly plant-based dietary patterns, like the traditional Mediterranean diet, still contain high levels of sodium, offsetting, in part, the potential benefits of cardiovascular prevention (2). Therefore, it is imperative that we consider the importance of sodium reduction in the prevention of non-communicable diseases (3) and place great emphasis on it in plant-based dietary guidelines.

Another important limitation to highlight is the use of often unreliable, incomplete data from observational studies. Cause-effect relationships are difficult to derive from such data thus reducing the certainty of the results. This emphasises the need for more randomised controlled trials which are rare in nutritional research. Carrying out more controlled clinical trials would also allow us to better gauge an estimate of the comparative benefits of different plant-based diets. For example, in our recent meta-analysis on the effect of plant-based dietary patterns on blood pressure, a median of only 5 controlled clinical trials were found for each of the seven identified diets (4). Low confidence results were generated as a result of the small sample sizes of some of those diets. Therefore, more controlled clinical trials must be completed to advance our knowledge on the health effects of plant-based diets.

The final limitation is the reliance of modelling on evidence of efficacy rather than effectiveness. The implementation of guidelines will have to demonstrate the feasibility and explore barriers and facilitators in different settings, e.g. socio-economic, cultural, geographic, and political, to inform coherent policies. The EAT-Lancet commission has attempted this with their universal healthy reference diet (5).

Joshua Gibbs, BSc
Francesco P Cappuccio, DSc FRCP
University of Warwick, WHO Collaborating Centre for Nutrition, Warwick Medical School, Coventry CV4 7AL.
f.p.cappuccio@warwick.ac.uk

No conflicts of interest declared

References
1. Afshin A, Sur PJ, Fay KA, et al. Health effects of dietary risks in 195 countries, 1990–2017: a systematic analysis for the Global Burden of Disease Study 2017. Lancet 2019; 393: 1958-72.
2. Sacks FM, Svetkey LP, Vollmer WM, et al. Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. N Engl J Med 2001; 344: 1-10.
3. Aburto NJ, Ziolkovska A, Hooper L, et al. Effect of lower sodium intake on health outcomes: systematic review and meta-analysis. Br Med J 2013; 346: f1326
4. Gibbs J, Gaskin E, Ji C, et al. The effect of plant-based dietary patterns on blood pressure: a systematic review and meta-analysis of controlled interventional trials. J Hypertens 2020; 38: in press (doi: 10.1097/HJH0000000000002604)
5. Willett W, Rockström J, Loken B, et al. Food in the Anthropocene: the EAT–Lancet Commission on healthy diets from sustainable food systems. Lancet 2019; 393: 447-92.

Competing interests: No competing interests

20 July 2020
Joshua Gibbs
Bio-Medical Student
Prof Francesco P Cappuccio
University of Warwick
School of Life Sciences and Warwick Medical School, Gibbet Hill Road, Coventry CV4 7AL