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. 2025 Apr;121(4):882-891.
doi: 10.1016/j.ajcnut.2025.01.016. Epub 2025 Jan 24.

Describing the landscape of nutrition- and diet-related randomized controlled trials: metaresearch study of protocols published between 2012 and 2022

Flávia Moraes Silva  1 , Amanda Rodrigues Amorim Adegboye  2 , Celeste Naude  3 , Cintia Curioni  4 , Fabio S Gomes  5 , Gary S Collins  6 , Gilberto Kac  7 , Jennifer Anne de Beyer  6 , Jonathan Cook  8 , Leila Cheikh Ismail  9 , Matthew J Page  10 , Neha Khandpur  11 , Sallie Lamb  12 , Sally Hopewell  8 , Shaima Saleh  13 , Shona Kirtley  6 , Simone Bernardes  1 , Solange Durão  14 , Colby J Vorland  15 , Michael Maia Schlussel  16
Affiliations

Describing the landscape of nutrition- and diet-related randomized controlled trials: metaresearch study of protocols published between 2012 and 2022

Flávia Moraes Silva et al. Am J Clin Nutr. 2025 Apr.

Abstract

Background: Publishing protocols promotes transparency and reproducibility. The scope and methods of protocols for nutrition- and diet-related randomized controlled trials (RCTs) have not been investigated yet.

Objectives: This study aims to map the landscape of nutrition- and diet-related interventions research.

Methods: We conducted a metaresearch of nutrition-and diet-related RCT protocols published between January 2012 and March 2022, in any language, targeting human participants, evaluating nutrition interventions isolated or combined. A systematic search of the literature was conducted in 6 online databases. Bibliometric information, study characteristics, and research transparency practices data were collected from the included publications. The instructions for authors of journals with publications in our sample were checked for endorsement of reporting guidelines. Mentions to reporting guidelines in the included protocols were also checked.

Results: Among the 62,319 records retrieved, 1068 were eligible. The number of published protocols increased annually, with a mean of 103 (range: 32-163) publications/y. Protocols were published in 148 journals, 50 of them (33.8%) endorsed Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT), 111 (75.3%) Consolidated Standards of Reporting Trials (CONSORT), and 4 (2.7%) Template for Intervention Description and Replication (TIDieR), whereas 343 (32.1%) protocols mentioned SPIRIT, 297 (27.8%) CONSORT, and 20 (1.9%) TIDieR. Most protocols reported the RCT registration number (n = 1006; 94.2%) and included statements about conflicts of interest (n = 952; 89.1%) and funding (n = 994; 93.2%). About two-thirds of protocols focused on adults or elderly participants (n = 677; 63.4%). Most protocols described 1 isolated nutrition- or diet-related intervention (n = 724; 67.8%), which were most frequently "supplementation, supplements or fortification" (n = 405; 37.9%) or "nutrition education, counseling or coordination of care" (n = 354; 33.1%). The most frequent primary outcomes reported were related to clinical status (n = 308; 28.8%).

Conclusions: The number of protocols for nutrition- or diet-related RCTs published is increasing, supporting the raising awareness and the importance of promoting these publications. The support and mention of relevant reporting guidelines by journals and researchers, respectively, remain far from ideal.

Keywords: interventions; metaresearch; nutrition; protocols; randomized controlled trial; reporting guidelines; research transparency.

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Conflict of interest statement

Conflict of interest FMS received a postdoctoral fellowship from COPPETEC Foundation for the conduct of this work. MMS, SK, JAdB, and GC were funded by Cancer Research UK (grant C49297/A27294) at the time this research took place. MJP is supported by an Australian Research CouncilDiscovery Early Career Researcher Award (DE200101618). CJV has received honoraria from The Obesity Society and his University has received funds to support his research from: National Cattlemen’s Beef Association; Alliance for Potato Research and Education; the Gordon and Betty Moore Foundation; and NIH.

Figures

FIGURE 1
FIGURE 1
Flow chart of the selection of nutrition- and diet-related RCT protocols, published 2012–2022. RCT, randomized controlled trials. ∗∗Records excluded for not meeting the eligibility criteria, as evidenced by screening their titles and abstracts.
FIGURE 2
FIGURE 2
Number of nutrition- and diet-related RCT protocols published between 2012 and 2022 by year and journal scope (∗corresponding to the first 3 mo of 2022). RCT, randomized controlled trials.
FIGURE 3
FIGURE 3
Geographical distribution of nutrition- and diet-related RCT protocols published between 2012 and 2022. Absolute (relative) frequency given by continent. Intensity of shading indicates absolute frequency by country. RCT, randomized controlled trials.
FIGURE 4
FIGURE 4
Relative frequency of nutrition- and diet-related RCT protocols published between 2012 and 2022 that referenced SPIRIT, CONSORT, and TIDieR. RCT, randomized controlled trials; SPIRIT, Standard Protocol Items: Recommendations for Interventional Trials; TIDieR, Template for Intervention Description and Replication.
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References

    1. Zabor E.C., Kaizer A.M., Hobbs B.P. Randomised controlled trials. Chest. 2020;158(1S):S79–S87. doi: 10.1016/j.chest.2020.03.013. - DOI - PMC - PubMed
    1. Li T., Boutron I., Al-Shahi Salman R., Cobo E., Flemyng E., Grimshaw J.M., et al. Review and publication of protocol submissions to Trials—what have we learned in 10 years? Trials. 2016;18(1):34. doi: 10.1186/s13063-016-1743-0. - DOI - PMC - PubMed
    1. International Committee of Medical Journal Editors, Recommendations for the conduct, reporting, editing, and publication of scholarly work in medical journals [Internet]. [cited May 22, 2023]. Available from: https://www.icmje.org/. - PubMed
    1. Schönenberger C.M., Griessbach A., Taji Heravi A., Gryaznov D., Gloy V.L., Lohner S., et al. A meta-research study of randomised controlled trials found infrequent and delayed availability of protocols. J. Clin. Epidemiol. 2022;149:45–52. doi: 10.1016/j.jclinepi.2022.05.014. - DOI - PubMed
    1. Chan A.W., Hrobjartsson A. Promoting public access to clinical trial protocols: challenges and recommendations. Trials. 2018;19(1):116. doi: 10.1186/s13063-018-2510-18. - DOI - PMC - PubMed

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