BRITAIN faces a looming food crisis because of the war against Iran, ministers conceded today.Chicken and pork could be among the items disappearing from supermarket shelves by the summer, with the government planning emergency measures to combat shortages.The US-Israeli aggression against Iran has shut the Straits of Hormuz, impacting on the supply of carbon dioxide (CO2), among other things.CO2 is vital to the storage of meats and salads, as well as being used in brewing and other vital processes from MRI scanning to water purification.