Food commodity prices have recently increased sharply and become more volatile, highlighting greater uncertainty in markets and threatening global food security. High fuel prices combined with legislative mandates have increased biofuel production raising the average cost of food on the global market and particularly in developing countries and established a link between crude oil and agricultural prices. We investigate the role of biofuels in explaining increased volatility in food commodities. Multivariate GARCH models and volatility decompositions are estimated on grains and crude oil daily prices over a twelve-year sample from 2000-2011. We find increases in correlations and co-movements between grains and crude oils prices after 2006 and particularly in 2008 when crude oil prices were high. Increased volatility in grains during the 2008-09 spike was largely due to shocks transmitted from crude oil to grains especially corn, wheat and soybean prices.