In recent years, Large Scale Land Acquisitions (LSLA), direct land tenure changes have been gaining momentum in developing countries. In this study, we evaluate the potential extent to which agricultural land deals in Africa are able to address the host countries' food security needs, a commonly cited motivation for their establishment. First, we develop a framework to evaluate the priority food security needs of 38 African countries in 2000 based on indicators of food availability, accessibility, stability, and utilization. Second, we estimate whether the crops from land deals would be sold on export or local food markets based on the origin of investments (domestic, foreign or mixed), type of investors (eg. agribusiness, finance, or government) and the intended crops (eg. food, cash crop, or biofuel). This enables us to estimate how likely the investment is to improve in-country food security, versus serving other purposes (e.g., speculation, enclosure of natural resources). Third, we account for the characteristics of the locations where the deals happen (population density, land cover and distance to markets) in order to estimate the level of conflict and deforestation that they could exacerbate. We find that LSLA are only likely to address the identified food security needs of 7 countries. LSLA are also at risk of increasing land pressures and conflicts or deforestation on 83% of the acquired area, including in countries where they could meet food security needs. We also find that the more productive lands are most often allocated to flex crops, while food crops are produced on more marginal lands. We thus argue that even when their purpose is agricultural production, most LSLA are not likely to improve food security; rather, they often serve the financial interests of transnational companies and local elites with the support of host governments. Finally, we recommend agricultural investments to be elaborated in consultation with local communities and marginalized groups to sustainably support their socio-ecological systems.