Surgical solutions to obesity can correct severe obesity, but what effect do they have on the body’s ability to extract nutrients from meals? After experiencing a drastic reduction in the ability to consume food—and, in some surgeries, skipping over some of the nutrient-absorbing parts of the digestive tract—bariatric patients may suffer from nutrient deficiencies.
Researchers from the University of Wollongong in Australia reviewed pre- and post-surgical data about patients who underwent bariatric surgery at a Sydney hospital. The goal of the study was to determine whether bariatric surgery causes nutritional deficiencies, and whether certain surgeries cause worse deficiencies than others.
Types of Bariatric Surgeries
The researchers, led by Seok Yee Toh, identified three types of bariatric operations:
Adjustable gastric banding, also called a lap band. The surgeon uses a silicone band to seal off most of the patient’s stomach, creating a small pouch into which the patient’s meals are deposited. Because the available amount of stomach is greatly reduced, the patient will experience a full feeling much sooner.
Roux-en-Y gastric bypass, often known simply as a gastric bypass, which is the most common type of bariatric surgery. The surgeon detaches a small section of the stomach from the rest of the stomach and connects it to the small intestine. When the patient digests a meal, the food is re-routed around some of the small intestine.
Sleeve gastrectomy, which is similar to the Roux-en-Y but bypasses more of the small intestine. The surgeon detaches the part of the stomach that lies along its larger curve and uses that section to create a small pouch, so that the patient is only able to consume about 150 milliliters of food. The surgeon bypasses the majority of the small intestine by attaching the top of a small piece of intestine to the stomach pouch and the bottom of the piece of intestine closer to the colon.
Before Bariatric Surgery, Patients Showed Some Nutritional Deficiencies
In this study, more than half of the patients who went to the Sydney hospital for bariatric surgery were already suffering from a Vitamin D deficiency. Many studies of obese patients report that between 60 and 80 percent have Vitamin D deficiencies, but science offers no clear explanation. In addition, a much smaller number of the Australian patients showed signs of being in the early stages of iron deficiency.
Post-Operative Nutrient Deficiencies Worsen
Iron deficiency was much more prevalent after bariatric surgery than before. There are two possible reasons. Food skips the parts of the intestine that absorb the most iron, so there’s less opportunity to extract it after mealtime. Also, because the stomach pouch doesn’t make hydrochloric acid, less iron might be removed from food.
Vitamin B12 deficiency was also more common after surgery. It appears to be most common in gastric bypass patients, because Vitamin B12 is absorbed through the gastrointestinal tract in a complicated series of events.
According to the authors, Folate can still be absorbed to a sufficient degree by the small intestine after a gastric bypass. For this reason, when patients have folate deficiencies, it’s usually because of low dietary intake or non adherence to multivitamin supplementation.
Calcium deficiency, which is most common in gastric bypass patients, has several possible causes: reduced dietary intake, insufficient absorption in the gastric pouch because of a decreased level of stomach acid, bypassing the parts of the digestive tract where calcium is usually absorbed and vitamin D deficiency.
Managing Post-Operative Nutrient Intake
Many pre-menopausal women who have undergone bariatric surgery take iron supplements, as the loss of blood during menstruation puts them at higher risk for iron deficiency and anemia. Vitamin B12 supplements will probably be needed. Because of the reduced ability to absorb it, the doses will have to be very high.
According to the study, patients should take 800 IU vitamin D per day and at least 1500 milligrams of calcium per day to avoid losing bone density.
In general, proper supplementatios is considered the best way to prevent nutritional deficiency after weight loss surgery.