Chronic gastritis causes deterioration and atrophy of the lining of the stomach, leading to the loss of functionof the parietal cells. The source of intrinsic factor is lost, which results in an inability to absorb vitamin B12, leading to development of pernicious anemia. Clients must increase their intake of vitamin B12 by increasing consumption of foods rich in this vitamin, such as nuts, organ meats, dried beans, citrus fruits, green leafy vegetables, and yeast.