What the best diet is has always been an area of contention. But one thing is clear: Meat is not necessary for health or fitness, and a diet high in plant proteins may well be especially healthy (e.g. Herpich et al., 2022). Further, plant- rather than animal-based diets leave a lower carbon footprint. So what might hold people back from adopting a plant-based diet? One reason is that people may understandably approach their doctor for advice; and the doctor may advise against it, given that many doctors are not well trained in nutrition (Crowley et al., 2019).

Espinosa et al. (2022) conducted a randomised control trial on French general practitioners with 200 doctors given a leaflet and access to an online platform, and 200 controls. The information in the materials concerned the health benefits of plant-based diets, and what nutrients (e.g. B12) may be deficient and what may not be. Attitudes towards and knowledge about plant-based diets was assessed. On a scale of 0-100% expressing whether they would advise for or against (0 = not at all, 100 = absolutely), the intervention shifted attitudes making them more positive about plant based diets by 17 percentage points. However, knowledge of specifically what is worth testing for (e.g. is zinc deficiency more probable or not?) did not change much. The research shows just what can be achieved by a small leaflet (shifting attitudes) and what may require more extensive training (knowledge of relevant medical practice).

The Stage 2 manuscript was evaluated over one round of in-depth review. Based on the responses to the reviewers' comments, the recommender judged that the manuscript met the Stage 2 criteria and awarded a positive recommendation.
 
URL to the preregistered Stage 1 protocol: https://osf.io/fc9gp
 
Level of bias control achieved: Level 6. No part of the data or evidence that was used to answer the research question existed prior to Stage 1 in-principle acceptance.
 
List of eligible PCI RR-friendly journals:

 

1. Crowley, J., Ball, L. & Hiddink, G. J. (2019.) Nutrition in medical education: a systematic review. Lancet Planetary Health. 3, e379–e389. https://doi.org/10.1016/S2542-5196(19)30171-8

 

2. Herpich, C., Müller-Werdan, U., & Norman, K. (2022). Role of plant-based diets in promoting health and longevity. Maturitas, 165, 47-51. https://doi.org/10.1016/j.maturitas.2022.07.003

 

3. Espinosa, R., Arpinon, T., Maginot, P., Demange, S. & Peureux, F. (2022). Removing barriers to plant-based diets: assisting doctors with vegan patients, acceptance of Version 2 by Peer Community in Registered Reports. https://osf.io/kq6eh?view_only=66eab29c7acb4aebbcec4631cbcb9217