[From a hypothesis to dietary advice--roads, short cuts and dead-end roads]

Few scientific fields receive more public attention than food and nutrition and few have more self-proclaimed experts. Many are confused by the jungle of dietary advice, sometimes widely differing, with the media often giving broad attention to isolated results without assessing them in the context of the total body of knowledge within a field. A new hypothesis may be received with enthusiasm by lay people and professionals alike, but the road to a well-documented conclusion on which to build general advice, is most often long. A finding must be seen in the context of other findings and judged in relation to the whole body of theory within a field before conclusions can be drawn. Work is carried out both nationally and internationally in order to reach a shared understanding of the minimum requirements of documentation before advice can be given. Traditional guidelines for evidence-based medicine can be applied to some but not all aspects of the science of nutrition. This article presents the process leading to official dietary guidelines in Norway.