Gastric bypass surgery reroutes your digestive tract in a way that can affect nutrient absorption. The surgery divides the stomach into a small upper section, or pouch, and a large bottom section, which is no longer used. The pouch is connected to a portion of the small intestine lower than normal, causing the body to absorb fewer calories, as well as fewer nutrients. After surgery, there is a risk of deficiencies in iron and calcium, as well as certain B vitamins.
Calcium and Vitamin D
Calcium is mainly absorbed in the duodenum and upper jejunum, portions of the intestine that are bypassed after surgery. Vitamin D helps calcium be absorbed in these areas. After surgery, since absorption is less efficient in the lower jejunum, a calcium and vitamin D deficiency might occur. After surgery, some patients may eat less calcium- and vitamin D-rich foods also, due to poor tolerance. This can increase the risk of deficiency. Most programs recommend patients take a daily supplement of 1,500 to 2,000 mg of calcium with vitamin D per day.
Iron
Iron is also best absorbed in the duodenum and upper jejunum. Deficiencies are usually related to poor absorption as well as a decreased intake from the diet. Meats contain high amounts of iron; however, many patients cannot tolerate meat after surgery, particularly red meats or tough cuts of meat since they are more difficult to digest. Patients with iron deficiencies usually feel great fatigue. Supplementation is often required after surgery, with a common dose of 18 to 27 mg of elemental iron each day.
Vitamin B-12
Vitamin B-12 is needed for red blood cell health, and a deficiency can lead to a specific anemia called macrocytic. After a gastric bypass surgery, you will not be able to fully digest and release the vitamin B-12 found in protein foods. The body's stores of vitamin B-12 are typically used up about a year after the surgery. A deficiency in vitamin B-12 can result in nerve damage. Vitamin B-12 supplements are needed after surgery, in a recommended dose of 1,000 mcg monthly, if taken by intramuscular injection, or 350 to 500 mcg daily, orally.
Vitamin B-1
Thiamin is another B vitamin that has an increased risk of deficiency after gastric bypass. Thiamin is a water-soluble vitamin absorbed in the upper jejunum. Prolonged vomiting, coupled with a lowered intake of thiamin foods and decreased absorption may result in a deficiency. Thiamin deficiency can lead to permanent defects in your short-term memory. Patients are typically required to take two multivitamins each day after surgery, and the amount of thiamin is enough to meet your needs. Prolonged vomiting may require additional supplementation.
References
- MedlinePlus: Gastric Bypass Surgery
- "Surgery for Obesity and Related Diseases"; ASMBS Allied Health Nutritional Guidelines for the Surgical Weight Loss Patient; L. Aills, et al.; March 2008
- ScienceDaily; Gastric Bypass Surgery May Cause Post-Op Nutrient Deficiencies; Oct. 16, 2007
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