An important gap exists between the statistical results presented in nutrition research papers and practitioners’ ability to interpret and apply these findings in clinical practice and policy. Recent research led by Drs. Bradley C. Johnston and Nirjhar R. Ghosh, together with the EvidenceBasedNutrition.org team, examined evidence-based practice competencies among nutrition professionals and students. The findings reveal that many practitioners – like their counterparts across other healthcare disciplines – would benefit from additional training in interpreting statistical results (e.g. relative vs absolute estimates of effect, determining clinical important differences among outcomes that matter to clients) and applying the results to practice and policy. This disconnect suggests an opportunity to improve how nutrition professionals are trained to translate scientific evidence into clinical recommendations for their clients.
A comprehensive systematic review of the research on evidence-based practice competencies included over 1,000 nutrition professionals and students. Results revealed that knowledge and skills for interpreting research evidence, in particular statistical results, could be improved upon. In particular, while dietitians have good knowledge and skills in understanding study designs and finding the research evidence to help answer clinical questions, based on the only comprehensive review of evidence-based practice skills by Dr. Johnston and team, there is limited to no evidence conducted in nutrition students and professionals on their understanding of treatment effect sizes or concepts specific to certainty (quality) of evidence for an effect size. This does not mean they do not have this knowledge and skillset, it just means it has not been studied or if it has it has not been well documented in the published literature addressing competencies in evidence-based practice.
In a recent 2024 Workshop hosted by Dr. Johnston on Evidence-Based Nutrition Practice with over 230 participants, primarily nutritionists or dietitians from over 34 countries, only 35% of participants correctly answered questions on effect size, p-values and 95% confidence intervals, while 67% correctly answered questions on searching the literature for evidence to address client questions and cases.
The key method to improve such knowledge and skills would involve standardized training across all dietetics programs specific evidence-based practice competencies. And to include more board exam questions on evidence-based practice competencies. Comprehensively training dietitians in evidence-based practice could impact patient care as nutrition professionals, helping clients to determine clinically meaningful research findings when considering clinical recommendations for their clients.
The Foundation of Evidence-Based Nutrition Practice
Evidence-based nutrition practice follows the same foundational principles established in medicine decades ago. As Bradley C. Johnston, a leading researcher in research methodology as applied to clinical care and policy at Texas A&M University, explains, this approach involves three key components: “You start with a clinical question or a public health (population) question, and you need to be very clear in terms of what exactly your question is… And then when you have a very clear, clean, structured question, you look to the literature for the best available evidence to answer that question.”
The second component involves applying clinical and real-world experience alongside the evidence. This step acknowledges that even high-quality research cannot account for every nuance for individual client or patient care. Clinicians must draw on their professional judgment (e.g. medical testing, differential diagnosis, likelihood of adherence)—shaped by hands-on experience and familiarity with various patients or clients—to interpret how research findings may best apply to specific clinical cases.
The final component involves sharing the best available evidence with patients or clients, allowing their health-related values and preferences to drive treatment decisions rather than having the evidence or a clinician dictate choices. For example, sharing the evidence (best estimate of effect together with the certainty of evidence for estimates, from high to low, for the health outcomes that matter most to one’s client. A client, for example, with type 2 diabetes may prioritize weight loss, insulin resistance control and dietary satisfaction. With the best available evidence in hand for these outcomes, what is the trade-off of benefits vs potential harms for a change in diet, and what are the costs and potential inconveniences for a change in diet. This person-centered approach promotes a helpful shift from older, traditional, authority-based clinical and public health practice to a collaborative decision-making approach.
Further Training and Research Gaps Revealed
The systematic review also revealed that most assessments relied on self-reported perceptions rather than objective measurements. Only one of the 12 studies examined used objective questions to assess actual knowledge and skills, and further studies are needed using objective measures that test clinicians competencies. Dr. Johnston goes on to say “While there may be perceived consensus in some areas of nutrition, that does not mean that the science is settled, and that the consensus is based on evidence-based principles, including high-quality, up to date systematic reviews and practice guidelines. Further, nutrition guideline recommendations should be based on the values and preferences of the target patient, client or patient population, a research area that EvidenceBasedNutrition.org has extensively invested in over the past 5 years.” Regardless of what the guidelines say, clinicians will always have to apply the best available evidence to the client in front of them, not the average client used to inform practice guidelines.
Unique Challenges in Nutrition Research
Nutrition research presents distinct challenges compared to pharmaceutical studies. As Johnston explains, “When appraising a study, the first thing that I look for is a study protocol, especially when I’m looking at human studies.” The need for a detailed study protocol is crucial, particularly in nutrition studies that often lack true placebos, involve complex dietary interventions that are difficult to blind (at least among the study participants but not data collectors and analysts), and typically require participants to replace one food with another rather than simply adding or removing items from their diet. One still needs an average of 1600 to 3000 calories per day depending on weight, muscle mass, age, activity level, etc. When reducing a food or beverage, it is typically substituted with another.
This substitution effect complicates the interpretation of results, as observed effects may reflect the replacement food rather than the intervention itself. Additionally, many nutrition interventions aim to modify existing exposures rather than introduce entirely new substances, making it difficult to establish clear cause-and-effect relationships.
Human nutrition research is hard to do, often comes with uncertain results, uncertainty that is not often expressed in published results, and is under funded. Under funding particularly with respect to well conducted randomized clinical trials that measure outcomes that patients and members of the public care about (e.g. quality of life, dietary satisfaction, mortality risk).
The Nutrition Users’ Guides: A Structured Solution
To address these gaps, Johnston and colleagues have developed the Nutrition Users’ Guides, an ongoing series of structured articles published in the journal BMJ Nutrition, Prevention & Health. These Guides provide step-by-step instructions for evaluating standard research designs in nutrition (e.g. clinical trials, observational studies, systematic reviews), addressing three key components: assessing methodological quality of a research article, interpreting the study (statistical) results, including the magnitude and precision of effects, and applying results to specific patient or population scenarios based on the target audience’s health-related values and preferences.
The guides are designed to empower clinicians, health service workers, and policymakers to better understand the validity, interpretability, and applicability of nutrition literature while helping practitioners and their clients make more informed, evidence-based, and value-sensitive nutrition decisions.
Implications for Training and Practice
The research findings suggest that current nutrition education approaches may be inadequate. The systematic review to support the need for these guides found that guidance from governing bodies, such as the Accreditation Council for Education in Nutrition and Dietetics, while they are improving, they still tend to be “quite vague” regarding specific evidence-based practice competencies.
Current accreditation standards give programs flexibility in defining where and how to incorporate evidence-based practice training into their curricula. While this allows for program diversity, it also creates the possibility for significant variation in how evidence-based practice competencies are understood, taught, and applied among nutrition professionals and students.
Bradley C. Johnston and his colleagues hope for a more standardized, objective training program in evidence-based practice competencies. This would ensure that nutrition professionals can more effectively communicate research findings to patients and collaborate with their allied medical colleagues. The researchers recommend incorporating these competencies into continuing education requirements and into registered dietitian board examinations to ensure consistent instruction across training programs in the profession.
Building Better Practice and Policy
The development of structured guidance by way of Nutrition Users’ Guides for evaluating nutrition literature represents a significant step toward enhancing evidence-based practice competencies, and ultimately evidence-based nutrition practice and policy. As the field continues to grapple with complex diet-disease relationships, deals with a growth plethora of “health influencers” on social media (who often promote products with little to no credible evidence), and as the field moves toward “precision nutrition” approaches, these Guides will help ensure that nutrition professionals and policymakers have robust skills in evidence evaluation.
The ultimate goal remains to help the profession optimally guide clients, patients and members of the public to make informed nutrition decisions based on the best available evidence and their values and preferences, promoting shared decision-making between nutrition professionals and their clientele. As the role of nutrition for chronic disease prevention and management becomes more widely endorsed and integrated (See New England Journal of Medicine Nutrition in Medicine series), the ability of nutrition professionals and their medical colleagues to objectively appraise, interpret and apply research evidence will become increasingly essential.
