Diets containing the highest levels of dairy products are associated with greater eutrophication potential but higher nutrient intakes and lower financial cost in the United Kingdom.

Previously, the nutritional contribution, environmental and financial costs of dairy products have been examined independently. Our aim was to determine the nutritional adequacy, financial cost and environmental impact of UK diets according to dairy content. In this cross-sectional study of adults (19-64 years) from the UK National Diet and Nutrition Survey years 1-4 (n = 1655), dietary intakes assessed from 4-day estimated food diaries were organized into quartiles (Q) total grams of dairy (milk, cheese, yogurt, dairy desserts) and analyzed using ANCOVA controlling for age, sex and energy intake with Bonferroni post hoc test for nutritional adequacy, Alternative Healthy Eating Index (AHEI-2010), environmental impact [greenhouse gas emissions (GHGE), eutrophication and acidification potentials], financial cost, markers of health and cardio-metabolic diseases. Nutritional adequacy, particularly for protein, calcium and iodine (+ 18 g, + 533 mg, + 95 g, respectively, all P < 0.0001) and AHEI-2010 (P < 0.0001) were significantly higher and systolic BP (- 2 mmHg, P = 0.019) was significantly lower for the higher-dairy diets (Q4, 274-1429 g/day dairy), compared with diets containing lower dairy (Q1, 0-96 g/day dairy). Diets in Q4 had lower financial cost (- 19%, P < 0.0001) and the greatest eutrophication potential, compared with Q1 (+ 29%, P < 0.0001). Yet the environmental (GHGE) and financial costs per unit nutrient (riboflavin, zinc, iodine, magnesium, calcium, potassium) were lower in Q4 than Q1 (all P < 0.0001). Diets with the highest dairy content had higher nutrient composition, better diet quality, were associated with lower BP and financial cost, but with higher eutrophication potential. Robust environmental data for many of food groups are limited and this needs an urgent addressing. This trial was registered on clinicaltrials.gov as NCT03407248.