Planetary health diet and cognitive decline in Chinese older adults: Balancing health benefits and environmental sustainability

The planetary health diet (PHD) proposed by the EAT-Lancet Commission, advocates for reduced meat and dairy intake while emphasizing the consumption of whole grains, fruits, vegetables, nuts, and legumes. Existing studies have shown that the PHD can lower mortality rates and slow cognitive decline in various populations. However, its specific effects on cognitive impairment among elderly individuals in China remain unclear, primarily due to regional socioeconomic and cultural differences. This study utilizes data from the Chinese Longitudinal Healthy Longevity Survey (CLHLS) to create the animal diet index (ADI) and the planetary health diet index (PHDI). We employed multivariable Cox proportional hazards regression models to assess the associations between these dietary indices and the risk of cognitive impairment in elderly participants. The research also examines the impact of grain intake and its relationship with environmental indicators, including greenhouse gas emissions, water footprint, and land use. Our results reveal that a higher PHDI is significantly correlated with a lower risk of cognitive impairment (HR = 0.539), while a higher ADI is associated with an increased risk (HR = 1.379). Furthermore, increased grain intake is associated with reduced cognitive impairment (HR = 0.729). Notably, the PHDI is linked to greater environmental burdens, contrasting with the ADI's association with lower grain-related environmental impacts. Stratified analyses indicate the PHD is protective across most regions, while the risks associated with animal-based diets are consistent. These findings suggest that while adherence to the PHD and increased grain intake may enhance cognitive health, they may also reflect trade-offs with environmental sustainability across China. Consequently, this study informs dietary strategies that aim to balance health and environmental concerns, emphasizing the need for context-specific approaches to dietary transitions.