The World Food Program said Thursday that North Korea’s food production had increased for the third year in a row but that mothers and children still lacked sufficient vitamins, fat and protein in their diets. The agency’s representative in North Korea, Dierk Stegen, said that many children remained stunted because of those deficiencies. Mr. Stegen said that the government had focused on producing cereals, but that it needed a more diverse food supply. He said that about 80 percent of North Korean households lacked the essential amount of vitamins, minerals, fats and proteins in their diets. He said staple food production in 2013 had increased about 5 percent compared with last year, with about five million tons of milled cereals produced. There is a food deficit of 340,000 tons, most of which is expected to be filled by imports.