Prisen på mat har i snitt gått opp 40 % på ni måneder, og lagrene har ikke vært så lave på 30 år, sier FNs generalsekretær Ban Ki-moon til BBC.
The UN World Food Program (WFP) and other agencies may be forced to ration food aid, he said in a BBC interview.
He said shortages might be eased by a «green revolution» to transform farming methods in Africa.
Global food prices have risen by 40% in nine months and food reserves are at their lowest for 30 years.
The WFP is facing a $500m (£248m) shortfall in its attempts to feed 73 million people this year.
Mr Ban said that «many countries in particular in Africa they now have to pay double or triple the price for their bread,» and warned that this would lead to increased malnutrition.