The group arrive at their conclusions in which they describe current methods for developing clinical practice guidelines as “not suitable for nutrition” and answering relevant nutrition questions should drive nutrition guidance rather than evidence availability.
“Nutrition guidance serves multiple purposes, including promoting health and well being, maintaining adequate nutrition, combating dietary excesses and imbalances associated with non-communicable diseases, and protecting sustainable food systems,” the team outlined.
“However, existing nutritional guidelines often do not consider the right questions or fail to take full account of available evidence because they rely on methods borrowed from other fields.”
eLENA and Cochrane library
Led by professor Lisa Bero, a researcher in evidence-based health care at the University of Sydney, the team detail a series of flaws in current approaches to developing nutrition guidelines.
These include the use of observational trial designs to investigate nutrient interactions, dietary patterns, or food systems rather than randomised controlled trial that are the preferred choice in clinical studies.
Randomised trials also present problems when studying nutrition exposures or interventions, the team said although they point out that advances in trial design, such as pragmatic trials, can help improve problems related to generalisability of results.
Along with Susan Norris, a World Health Organization (WHO) scientist, the team point out that nutrition guidelines and policy statements in the WHO’s e-Library of Evidence for Nutrition Actions (eLENA) database of systematic reviews relate to single nutrient interventions, which can be evaluated by randomised trials.
They go on to highlight the majority of nutrition systematic reviews in the Cochrane Library relate to evidence derived from studies of specific nutrients rather than of foods, dietary pattern, or food systems.
As well as availability of evidence, selection of topics for systematic reviews may be affected by reviewers’ interest in narrower, clinical topics.
Logic models and theory
“Nutrition researchers and organisations such as Cochrane are calling for reform of conventional evidence synthesis and translation approaches,” the researchers said.
“This is so they are better able to overcome limitations in available evidence and include evidence relevant to modern nutrition problems.”
Along with questioning current methods for developing clinical practice guidelines and prioritising relevant nutrition questions over the availability of evidence, the team also advise the use of logic models and theory to develop more focused questions.
These questions can then go on aid in reviewing, identifying and evaluating the most suitable types of study as well as formulating recommendations.
The team also want to see innovation in evidence synthesis methods to assess the relevant proof.
“Although innovation is needed to fill some of the gaps in evidence synthesis methods, our approach offers opportunities for funders, researchers, and systematic reviewers to produce studies and synthesise evidence that can be used to inform optimal nutrition policy,” the team said.
“Involving these stakeholders and policy makers in improving the methods for systematic reviews in nutrition will make the reviews underpinning nutrition guidelines more rigorous, transparent, usable, and relevant.”
No ‘one size fits all’
However, Michael Peel, a General Practitioner from the UK asks whether making nutritional guidelines fit for purpose is possible beyond a simplistic level.
”Adaptation to new diets happens slowly,” Dr Peel said in response to the article. “For example, lactose tolerance is common in northern Europeans, with a different genetic mutation identified in those parts of east Africa where cattle rearing developed separately.”
“Few people whose forebears migrated into these areas have this tolerance. Separately we are learning about the importance of the microbiome in digestion, which appears to be as unique as a fingerprint.
“There is no "one size fits all" approach to nutrition, except that nobody has adapted to modern hyper processed foods.
“Some basic nutritional guidelines are essential, around balance, vitamins and minerals.
Maybe the only useful guideline is: "if neither of your grannies would recognise it, don't eat it.”
Published online: doi.org/10.1136/bmj.l1579
“Making nutrition guidelines fit for purpose.”
Authors: Lisa Bero, Susan Norris, Mark Lawrence