The FAO's price index, which measures monthly price changes for a basket of grains, oilseeds, dairy, meat and sugar, averaged 207.8 points last month as compared with 214.6 points in May 2013, falling nearly 3.2 per cent.
The maximum fall was witnessed in dairy prices.
Global Food Price Index showed a sharp jump in June.
The FAO price index measures monthly price changes for a basket of cereals, oilseeds, dairy products, meat and sugar.
Trend could continue on downward revision in winter harvests.
The FAO's food index of 55 items averaged at 209.3 points in April this year, down by 1.6 per cent from March and 3.5 per cent below April 2013.
It would also be the fifth month of consecutive drops in the index.
Dairy, sugar prices fall sharply, despite El Nio fears