Our hypothesis is that the Bonilla Index can be used as a consistent indicator of food security vulnerability to trade at national level. In this article, we test the assumption that, with the aim of stabilizing national food availability and accessibility, developing countries use policy instruments for stabilizing their Bonilla Index. After analysing the role of the national rate of assistance and of the exchange rate vulnerability of food security to trade, we first present the Bonilla Index evolution paths of 39 developing countries from 2005 to 2010. Second, we measure the impact of their national policy responses to 2008 price surge, by using the national rate of assistance on importable food products. Finally we test, statistically, the extent to which our qualitative hypotheses and relationships are actually confirmed by the data over the period 2005-2010. Our results suggest that most developing countries have used their possibility to play with the nominal rate of assistance level to compensate the effects of the 2008 food price surge, and that exchange rate variations actually have few impact on food accessibility for consumers in a context of volatility of food prices.