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7: Dietary guidelines and quality (Chapter 8c)

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    Abstract

    This chapter covers two related but distinct topics: Food-based dietary guidelines and assessment of population-level diet quality. Definitions of diet quality, food-based dietary guidelines, and assessment measures have all evolved over time, reflecting new and emerging scientific evidence for diet-health relationships.

    Food-based dietary guidelines are developed by national health authorities for use by consumers, practitioners, and policymakers. Such guidelines translate current scientific knowledge about relationships between food intakes and health outcomes into clear population-level guidance. In this chapter, we provide a brief overview of the development and communication of guidelines and describe a global repository for food-based dietary guidelines. We summarize areas of consistency across guidelines and highlight some possible future directions, including incorporation of environmental sustainability concerns.

    In the second part of the chapter, we describe approaches to assessing diet quality, particularly at the population level. Numerous metrics (indicators, indices, and scores) have been developed to summarize diet quality, reflecting different definitions of diet quality and also different measurement objectives. Widely used metrics include measures of adherence to national food-based dietary guidelines such as the U.S. Healthy Eating Index, measures of adherence to healthy regional diets such as Mediterranean diet scores and indices, and other measures developed based on epidemiological evidence linking dietary patterns and characteristics to health outcomes.

    Using a series of examples, we describe how diet quality metrics are developed, evaluated, and used. Most scores and indices require detailed quantitative dietary intake and food composition data. However, several measures have been developed for use in contexts where such data are not available and simpler measures are required, and we include examples of these. Finally, as with food-based dietary guidelines, concerns with environmental impacts of diets and food systems are growing, which will likely result in new metrics incorporating this dimension.

    This chapter covers two related but distinct topics: Food-based dietary guide­lines, often provided by national health authorities, and assess­ment of diet quality. The section on assess­ment of diet quality has a primary focus on applications at the popu­lation level, for monitoring diet quality, assessing diet-disease associ­ations, and evaluating policy and programmatic inter­ventions. The two topics in this section are linked in this popu­lation-level focus, and because assess­ment of diet quality is some­times approached through assessing adherence to national food-based dietary guide­lines. However, the section also covers a range of other approaches to assessing diet quality in popu­lations. Learning objectives for readers include gaining understanding of:

    • The role of food-based dietary guide­lines in communi­cating guidance from national health authorities;
    • The range of topics covered by food-based dietary guide­lines, and some areas of consistency and difference across various national guide­lines;
    • The evolution of definitions of diet quality, and how this has influenced assess­ment of diet quality;
    • The wide diversity of diet quality indices currently in use;
    • Some of the main types of indices, including those based on national food-based dietary guide­lines, on regional diets, and on other summaries of evidence for diet-health relation­ships;
    • How indices differ in their devel­op­ment, measurement (data sources), calculation and use;
    • Which indices have lower data require­ments for their calculation;
    • How new concerns with sustain­ability and planetary health may affect diet quality definitions and assess­ment.

    • 7.1: Food-based dietary guide­lines (8c.1)
      This page discusses the development of food-based dietary guidelines (FBDGs) by national authorities to promote healthy diets and combat non-communicable diseases. It underscores the need for evidence-based research, stakeholder input, and cultural relevance. FBDGs target all individuals but can be adapted for specific groups. Common visual themes and key messages align with WHO guidance, emphasizing dietary diversity and moderation.
    • 7.2: Assessing diet quality (8c.2)
      This page reviews the evolving definitions and metrics of diet quality, emphasizing their application at the population level. It discusses diverse indices developed for both affluent and resource-constrained settings, highlighting the importance of adaptability to cultural dietary patterns. The text describes two main index development approaches: "a priori" and "a posteriori," detailing the necessary decisions involved in their creation and the importance of validation. The U.S.
    • 7.3: Examples of diet quality indices (8c.3)
      This page discusses various diet quality indices, with a focus on the U.S. Healthy Eating Index (HEI), which evaluates adherence to dietary guidelines through a scoring system. The HEI allocates points for adequacy and moderation, validating its effectiveness in assessing dietary patterns and health outcomes. While primarily developed for adults, adaptations for children exist, and related indices are emerging in other countries.
    • 7.4: Alternate Healthy Eating Index (8c.4)
      This page discusses the Alternate Healthy Eating Index (AHEI), created by McCullough et al., which evaluates dietary adherence related to non-communicable diseases (NCDs). It prioritizes whole grains and lean proteins over red meats and incorporates a U-shaped scoring system for components like sugar-sweetened beverages and alcohol.
    • 7.5: Mediterranean Diet Score or Index (8c.5)
      This page discusses the Mediterranean diet, highlighting its plant-based focus and health benefits established since the mid-20th century. It details various Mediterranean Diet Scores (MDSs) used to evaluate adherence, including the Trichopoulou score, the 55-point MedDietScore, the 18-point MEDI-LITE score, and the newly developed 100-point Mediterranean-Style Dietary Pattern Score. The MDS assesses dietary habits through 13 components, adjustable for children and adolescents.
    • 7.6: Dietary Approaches to Stop Hypertension scores
      This page discusses the DASH diet, aimed at lowering blood pressure through increased consumption of fruits, vegetables, and low-fat dairy, while limiting red meat and sugar. It was first tested in a 1994 trial showing notable blood pressure reductions and later studies linked its adherence to reduced risks of various diseases.
    • 7.7: Healthy Diet Indicator (8c.7)
      This page discusses the Healthy Diet Indicator (HDI), a tool designed to evaluate adherence to WHO dietary guidelines. It has evolved through studies to prioritize nutrient intake over food groups. The original HDI had nine components, while the latest version, HDI-2020, assesses eleven components, including newer recommendations from the World Cancer Research Fund.
    • 7.8: Dietary Inflammatory Indices (8c.8)
      This page discusses the development of diet quality indices to evaluate the inflammatory potential of diets, particularly highlighting the Dietary Inflammatory Index (DII). The DII, relevant worldwide, scores foods based on their association with inflammatory biomarkers and is linked to non-communicable diseases (NCDs).
    • 7.9: Diet quality based on level of food processing (8c.9)
      This page discusses the NOVA classification, which organizes foods into four categories based on processing: unprocessed, processed culinary ingredients, processed foods, and ultra-processed foods (UPF). UPF, high in non-kitchen ingredients and common in diets, correlate with lower nutrient intake and higher health risks, such as obesity and chronic diseases. Effective diet quality assessments need comprehensive dietary intake data across different demographics.
    • 7.10: Lower-burden diet quality indices (8c.10)
      This page discusses dietary quality indices, highlighting the development of simpler assessment methods for low- and middle-income countries. Key metrics include the Global Dietary Recommendations Score (GDR Score), which focuses on dietary guideline adherence, and the Global Diet Quality Score (GDQS), which assesses nutrient adequacy and non-communicable disease risks using less intensive data collection.
    • 7.11: Incorporating sustain­ability in diet quality definitions and indices (8c.11)
      This page discusses the negative impacts of current food systems on the environment, leading to a push for healthier, sustainable diets. The EAT-Lancet Commission has proposed a "healthy reference diet" focusing on plant-based foods, but its limitations on nutrient-rich animal products have sparked debate. Additionally, various organizations are creating indices for sustainable diets aligned with national guidelines or the EAT-Lancet model, highlighting an evolving area for further research.
    • 7.12: Summary of diet quality indices (8c.12)
      This page explores various diet quality indices, highlighting their evolution in purpose and scope. These indices reflect adherence to dietary guidelines, nutrient adequacy, and the reduction of non-communicable disease risk. There is an emerging interest in indices that also consider planetary health. The section notes the difference between data-intensive indices and those designed for global application with lower data needs.

    This page titled 7: Dietary guidelines and quality (Chapter 8c) is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by Rosalind S. Gibson via source content that was edited to the style and standards of the LibreTexts platform.