I think one main challenge is to combine healthy diets with all other dimension of sustainability, be environment, socio-economics, processing and so on. For this, I think there are as many solutions as different situations worldwide. each country has its own problem of health, i.e., deficiencies, over- and uner-nutrition. Therefore, we have to think locally and develop sustainable healthy diets adpted to reality of each country. However, some global healthy guidelines can be defined, then we adapt them to local situations. Each country has not the same local productions, climate, food availability, etc.
Fardet Anthony