Guidelines Dietary - Eat For Health

How the Guidelines were developedThese Guidelines are an evolution of the 2003 edition of the dietary guidelines and build upon their evidence andscience base. New evidence was assessed to determine whether associations between food, dietary patternsand health outcomes had strengthened, weakened, or remained unchanged. Where the evidence base wasunlikely to have changed substantially (e.g. the relationship between intake of foods high in saturated fat andincreased risk of high serum cholesterol) additional review was not conducted.The methods used to analyse the evidence were in accordance with international best practice. 32,33 The mainmethods are summarised below and given in more detail in Appendix B.The Guidelines were further informed by substantial advances in the methodology for guideline development anduseability since publication of the previous edition of the dietary guidelines.Human feeding studies and clinical trials provide direct evidence of the impact of food consumption on physiologicalresponses and disease biomarkers. Although the breadth and depth of knowledge generated from these kinds ofstudies is uneven, a consistent alignment of results with plausible mechanisms adds confidence to the analysis ofall studies combined.Five key evidence sources for the GuidelinesIn developing the Guidelines, NHMRC drew upon the following key sources of evidence:• the previous series of dietary guidelines and their supporting documentation 34-36• the Evidence Report 33• the NRV Document 8• the Food Modelling System 9• key authoritative government reports and additional literature (including a commissioned review on pregnantand breastfeeding women). 37Evidence Report – answers to key questions in the research literatureThe NHMRC commissioned a literature review to answer targeted questions on food, diet and disease/healthrelationships covering the period 2002–2009. This addressed specific questions developed by the expert DietaryGuidelines Working Committee (the Working Committee), where evidence might have changed since the 2003edition of the dietary guidelines was developed (see Appendix D). 38The NHMRC followed critical appraisal processes to ensure rigorous application of the review methodology. 32,39Data were extracted from included studies and assessed for strength of evidence, size of effect and relevance ofevidence according to standardised NHMRC processes. 32,40-42 The components of the body of evidence – evidencebase (quantity, level and quality of evidence); consistency of the study results; clinical impact; generalisability; andapplicability to the Australian context – were rated as excellent, good, satisfactory or poor according to standardNHMRC protocols. 38,42The reviewers then summarised the evidence into draft body of evidence statements. The Working Committeeadvised that a minimum of five high quality studies was required before a graded evidence statement could bemade. The individual studies in meta-analyses were considered as separate studies. The evidence statementswere graded A to D according to standard NHMRC protocols: 42• Grade A (convincing association) indicates that the body of evidence can be trusted to guide practice• Grade B (probable association) indicates that the body of evidence can be trusted to guide practice inmost situations• Grade C (suggestive association) indicates that the body of evidence provides some support for therecommendations but care should be taken in its application• Grade D indicates that the body of evidence is weak and any recommendation must be applied with caution.Once the evidence statements had been drafted and graded, NHMRC commissioned an external methodologistto ensure that review activities had been undertaken in a transparent, accurate, consistent and unbiased manner.This was to ensure that the work could be double-checked easily by other experts in nutrition research.IntroductionNational Health and Medical Research Council5