Newly available evidence confirms that expansion of aggregate food supplies within developing countries themselves is strongly associated with reduced undernourishment. It is not sufficient to rely solely on aggregate economic growth or reductions in poverty incidence to deliver improved food security. But the evidence also shows that higher food prices significantly increase the rate of undernourishment. This paper looks into the underlying reasons for these two findings - why expansion in per capita availability of food and reductions in real food prices are so strongly associated with reductions in undernourishment and poverty incidence.