Assessing diet quality and associated environmental impacts: A cross-sectional analysis in a middle- to older-aged Irish population

Current dietary patterns have implications for both population and planetary health, giving dietary shifts the potential to reduce these impacts. However, higher quality diets are not inherently of lower environmental impact. This paper examines the association between diet quality, defined using the Dietary Approaches to Stop Hypertension (DASH) diet, Mediterranean (MED) diet and Healthy Eating Index 2015 (HEI-2015), and environmental impacts among middle- to older-aged adults. The cross-sectional analysis used a random sample of 1862 males and females aged 46–73 years. Diet quality scores (DQS) were derived from a validated food frequency questionnaire (FFQ). The impact of food production was estimated using greenhouse gas emissions (GHGE) and blue water use (BWU) environmental impact indicators from secondary data sources. Relationships between food groups, DQS and environmental impacts were evaluated via correlation and regression analyses. The food group red meat & offal was found to be the largest contributor to dietary GHGE and caffeinated beverages to BWU for all DQS and across all quartiles of adherence. The cumulative contribution of discretionary foods and beverages requires attention given they are superfluous to human health. In fully adjusted regression analyses, higher diet quality was associated with lower GHGE for all DQS. Conversely, higher diet quality was positively associated with water use (DASH and MED only). Encompassing principles of the DASH and MED diets in future dietary recommendations may reduce diet-related disease in later life and dietary GHGE. However, the increase of BWU as diets become healthier is a concern. Advocating for plant-based diets must be coordinated with sustainable production and supply. National solutions to increase self-sufficiency and reduce impacts and reliance on climate vulnerable countries is warranted. The population dietary shifts required for health and planet can only be realised by multi-level structural changes to food systems through policy, and not through sole expectation of individual change.