surgery, until their GI tract adjusts to the changes, and cannot eat adequate amounts even with 6 meals a day. Many patients require protein supplementation during the early phases of rapid weight loss to prevent excessive loss of muscle mass. Hair loss is also a risk of protein malnutrition. Vitamin A deficiencies generally occur as a result of fat-soluble vitamins deficiencies. This often comes after intestinal bypass procedures such as jejunoileal bypass (no longer performed) or biliopancreatic diversion/duodenal switch procedures. In these procedures, fat absorption is markedly impaired. There is also the possibility of a vitamin A deficiency with use of the weight-loss medication orlistat (marketed as Xenical and Alli). Folate deficiency is also a common occurrence in gastric bypass surgery patients. Nutritional effects After surgery, patients feel fullness after ingesting only a small volume of food, followed soon thereafter by a sense of satiety and loss of appetite. Total food intake is markedly reduced. Due to the reduced size of the newly created stomach pouch, and reduced food intake, adequate nutrition demands that the patient follow the surgeon's instructions for food consumption, including the number of meals to be taken daily, adequate protein intake, and the use of vitamin and mineral supplements. Calcium supplements, iron supplements, protein supplements, multi-vitamins (sometimes pre-natal vitamins are best), and vitamin B12 (cyanocobalamin) supplements are all very important to the post-operative bypass patient. Total food intake and absorbance rate of food will rapidly decline after gastric bypass surgery, and the number of acid-producing cells lining the stomach increases. Doctors often prescribe acid-lowering medications to counteract the high acidity levels. Many patients then experience a condition known as achlorhydria, where there is not enough acid in the stomach. As a result of the low acidity levels, patients can develop an overgrowth of bacteria. A study conducted on 43 post-operative patients revealed that almost all of the patients tested positive for a hydrogen breath test, which indicated an overgrowth of bacteria in the small intestine. Bacterial overgrowth causes the gut ecology to change and induces nausea and vomiting. Recurring nausea and vomiting eventually change the absorbance rate of food, contributing to the vitamin and nutrition deficiencies common in post-operative gastric bypass patients. Protein nutrition Proteins are essential food substances, contained in foods such as meat, fish, poultry, dairy products, eggs, vegetables, fruits, legumes and nuts. With reduced ability to eat a large volume of food, gastric