Introduction: 

Sustainable diets have gained global recognition as food systems contribute about 25% of global greenhouse emissions (GHGEs). Meeting the dimensions of nutritional adequacy, cultural acceptability, affordability, and environmental sustainability is complex, requiring careful consideration of synergies and trade-offs. Hence, synergies and trade-offs must be established. This study aimed to simultaneously minimise the cost and GHGE of diets for Ghanaian adults aged 19–50 years, while ensuring nutritional adequacy and cultural acceptability using locally available foods.

Method: 

A bi-objective optimisation framework employing the ɛ-constraint method was applied. Cost and GHGE were first solved individually using linear programming, then jointly optimised to generate solution sets. Nutrient requirements ensured adequacy, while food group constraints maintained cultural acceptability. A Pareto frontier was generated to visualise trade-offs between cost and GHGE.

Results: 

A clear trade-off was observed: as cost decreased, GHGE increased, and vice versa. The correlation between cost and GHGE was strongly negative (r = −0.93 for males; r = −0.95 for females), with cost explaining most of the variability in GHGE (R² = 0.87 and 0.90, respectively). Optimal diets involved modest adjustments, emphasising nutrient-rich and environmentally friendly foods. Food baskets across solutions included staples, seafood, fats and oils, fruits and vegetables, legumes, seeds, and nuts.

Implications: 

This study demonstrates the feasibility of applying multi-objective optimisation to Ghanaian diets, integrating affordability, nutrition, sustainability, and cultural acceptability. The findings provide novel evidence to guide policymakers, industry stakeholders, and consumers in promoting healthier and more sustainable diets in Ghana and similar West African contexts.