Approximately 300,000 gastric bypass operations are performed in the US every year. The goal of the operation is to reduce the size of the stomach pouch dramatically or 'bypass' it completely so that the individual feels very full after consuming even a small amount of food. There are many different types of operation, but the most popular one and is performed in over 2/3 of gastric bypass operations is called the 'Gastric Sleeve'. In order to leave a narrow 'sleeve' for food to pass into the intestine, most of the stomach is removed, which also removes all the parietal cells that produce Intrinsic Factor (IF) which leads to vitamin B deficiency and a lifelong dependence on vitamin B12 supplements.