Defining diet quality: a synthesis of dietary quality metrics and their validity for the double burden of malnutrition

Abstract

Achieving most of the UN Sustainable Development Goals requires a strong focus on addressing the double burden of malnutrition, which includes both diet-related maternal and child health (MCH) and non-communicable diseases (NCDs). Although, the most optimal dietary metric for assessing malnutrition remains unclear. Our aim was to review available global dietary quality metrics (hereafter referred to as dietary metrics) and evidence for their validity to assess MCH and NCD outcomes, both separately and together. A systematic search of PubMed was done to identify meta-analyses or narrative reviews evaluating validity of diet metrics in relation to nutrient adequacy or health outcomes. We identified seven dietary metrics aiming to address MCH and 12 for NCDs, no dietary metrics addressed both together. Four NCD dietary metrics (Mediterranean Diet Score, Alternative Healthy Eating Index, Healthy Eating Index, and Dietary Approaches to Stop Hypertension) had convincing evidence of protective associations with specific NCD outcomes, mainly mortality, cardiovascular disease, type 2 diabetes, and total cancer. The remaining NCD dietary metrics and all MCH dietary metrics were not convincingly validated against MCH or NCD health outcomes. None of the dietary metrics had been validated against both MCH and NCD outcomes. These findings highlight major gaps in assessing and addressing diet to achieve global targets and effective policy action.

Figure 1

Foods and nutrients included in the dietary metrics Shading indicates that the food or nutrient is included in the dietary metric (appendix pp 22–23). DDS=Dietary Diversity Score. FCS=World Food Programme's Food Consumption Score. FVS=Food Variety Score. HDDS=Household Dietary Diversity Score. IYCMDD=Infant and Young Child Minimum Dietary Diversity. MDD-W=Minimum Dietary Diversity for Women. WDDS=Women's Dietary Diversity Score. IDDS=Individual Dietary Diversity Score. AHEI=Alternative Healthy Eating Index. DASH=Dietary Approaches to Stop Hypertension. DGAI=Dietary Guidelines for Americans Adherence Index. DII=Dietary Inflammatory Index. DQI-I=Diet Quality Index-International. HEI=Healthy Eating Index. KIDMED=Mediterranean Diet Quality Index for Children and Teenagers. MED=Mediterranean Diet Score. PURE=Prospective Urban Rural Epidemiology Diet Score. RFS=Recommended Foods Score. WHO-HDI=WHO Healthy Diet Indicator. WCRF-AICR World Cancer Research Fund and American Institute for Cancer Research.

Figure 2

Screening and selection process of meta-analyses evaluating dietary metric-disease relationships *Study design or not relevant outcome or exposure.

Figure 3

Grading of evidence for associations of dietary metrics with maternal and child health (MCH) and non-communicable diseases (NCDs) based on meta-analyses and narrative reviews Dark shading indicates a meta-analysis, light shading indicates a narrative review, and no shading indicates that no review was identified. One plus sign indicates little evidence from few studies (<5), two plus signs indicate inconsistent results from a moderate number of studies (≥5), and three plus signs indicate consistent evidence from multiple high-quality studies (≥5). The relationship between a higher dietary metric and the health outcome was protective, unless stated otherwise. AHEI=Alternative Healthy Eating Index. DASH=Dietary Approaches to Stop Hypertension. DDS=Dietary Diversity Score. DII=Dietary Inflammatory Index. DQI-I=Diet Quality Index-International. FVS=Food Variety Score. WHO-HDI=WHO Healthy Diet Indicator. HEI=Healthy Eating Index. IYCMDD=Infant and Young Child Minimum Dietary Diversity. KIDMED=Mediterranean Diet Quality Index for Children and Teenagers. MED=Mediterranean Diet Score. RFS=Recommended Foods Score. WCRF-AICR World Cancer Research Fund and American Institute for Cancer Research.