Prevalence of Nutritional Deficiencies After Gastric Bypass

Nutritional deficiencies are fairly common after gastric bypass surgery. That's because part of the small intestine is bypassed and the small intestine is where we absorb most vitamins and minerals. Gastric bypass patients are advised to take a number of vitamin and mineral supplements daily, including multivitamins, calcium, iron and B12, and to have regular lab tests performed to check for nutritional deficiencies.

I recently conducted an informal survey of gastric bypass patients participating in an online support group to collect information about the prevalence of nutritional deficiencies. Since I found it very difficult to control for things like which supplements patients were taking when they developed deficiencies, this is not a scientific study. However, all patients reported taking at least a multivitamin daily. The results do provide some insight into the prevalence of nutritional deficiencies after gastric bypass surgery and which deficiencies might be most common.

Most commonly reported was vitamin D deficiency, present in 77 percent of people responding to the survey. It should be noted that vitamin D deficiency is also very common in the general population, not just in gastric bypass patients.

Iron deficiency was also common, with 54 percent of people responding to the survey having experienced that. Iron deficiency is not as common as vitamin D deficiency in the general population but it's not uncommon in menstruating women, either.

Vitamin B12 deficiency was also fairly common in gastric bypass patients responding to the survey, present in 46 percent of respondents. Vitamin B12 deficiency is reportedly rare in the general population but is fairly common in gastric bypass patients due to decreased intrinsic factor in the surgically created pouch.

Of all respondents, 23 percent reported vitamin A deficiencies. In addition to the malabsorption created by bypassing part of the small intestine, gastric bypass patients have difficulty absorbing beta carotene, a source of vitamin A found in many vitamin supplements. That's because they don't produce as much stomach acid as "normal" people and a fair amount of stomach acid is necessary for the absorption of beta carotene.

Fifteen percent reported vitamin B1 and vitamin B6 deficiencies. Some doctors do not routinely order lab tests to check for B6 deficiencies, though, so some of the respondents may have had B6 deficiencies that went undiagnosed. Fifteen percent also reported potassium deficiencies, which can be deadly if not treated promptly.

Eight percent reported deficiencies in vitamin K, zinc, copper and magnesium. Some doctors do not routinely order lab tests to check for vitamin K or copper deficiencies, though, so some of the respondents may have had vitamin K or copper deficiencies that went undiagnosed.

It should also be noted that the average person responding to the survey had experienced three different nutritional deficiencies since their surgery.

Sources:

American Society for Metabolic and Bariatric Surgery. http://www.asbs.org/Ne wsite07/resources/bgs_final.pdf . ASMBS Allied Health Nutritional Guidelines.