One of the most important factors which prevent developing countries from reaching a sustainable development is their vulnerability to international price shocks and to natural shocks. Opening trade with developed countries, which are far geographically and different in terms of production patterns could increase developing countries' vulnerability. On the one hand, this leads to a high concentration of their exports in primary commodities which results in greater vulnerability to terms-of-trade volatility. On the other hand, the dependence on food imports from the world suppliers, in particular during climatic shocks, threatens their food security. This thesis studies the extent to which an expansion of regional trade could reduce countries' vulnerability. The first two chapters show that fostering trade with regional and economically similar partners could contribute to increase export diversification. The third chapter provides a new examination of the main barriers preventing regional trade of staple foods between east and central African countries.