Associations Between Adherence to the EAT-Lancet Planetary Health Diet and Nutritional Adequacy, and Sociodemographic Factors Among Australian Adults

<b>Background/Objectives:</b> Adherence to the EAT-Lancet Planetary Health Diet (PHD) may promote human health and environmental sustainability, yet evidence regarding adherence and nutritional adequacy in Australia is limited. Globally, no research to date has used the recently updated 2025 PHD guidelines. We benchmarked the compatibility of Australian adults' dietary patterns with the 2025 PHD and examined its associations with nutritional adequacy and sociodemographic factors. <b>Methods:</b> This was a cross-sectional analysis of dietary data from 5655 adults who participated in the National Nutrition and Physical Activity Survey. Usual intakes were estimated from two 24 h recalls using the Multiple Source Method. PHD adherence was measured using the Healthy Reference Diet Score (0-130 points). Nutrient adequacy was assessed using the full probability method for iron and the Australian/New Zealand Estimated Average Requirement Cut-Point Method for all other nutrients. Survey-weighted regression models examined associations with nutritional adequacy and sociodemographic factors. <b>Results:</b> The mean PHD adherence score was 50 (SE 0.3) points. Higher adherence was associated with lower odds of inadequate intakes of several micronutrients, but with higher odds of inadequacy for vitamin B12 (OR: 1.24; 95% CI: 1.06, 1.45) and calcium (OR: 1.09; 95% CI: 1.01, 1.17). PHD adherence was higher among females, older adults, those with higher educational attainment, those born in countries where English is not the main language, two-person households and non-smokers; adherence was non-linearly associated with alcohol and was lower among those with a Body Mass Index ≥ 30 kg/m². <b>Conclusions:</b> PHD adherence in Australia was low. Higher adherence was associated with improved adequacy for several micronutrients. Trade-offs for vitamin B12 and calcium warrant consideration. Equity-conscious strategies will be needed to support the adoption of nutritionally adequate, environmentally sustainable diets.