ARTICLES 

Nutrient Deficiencies and Health Consequences

Part II: Gastric Bypass and Duodenal Switch

Cynthia Buffington, Ph.D.

Beyond Change, August 2002

Nutrient deficiencies following bariatric surgical procedures can lead to serious health consequences if left unattended. In last month’s issue of Beyond Change, pre-operative nutritional deficiencies and those following gastric restrictive surgeries (gastric band, gastroplasty procedures) were discussed, along with suggestions for nutrient management. This month, nutrient deficiencies following surgeries that contain a malabsorptive component, such as the gastric bypass and duodenal switch, are addressed.

Gastric bypass combines both gastric restriction and malabsorption to induce massive and sustained weight loss. With the gastric bypass, the amount of food one can consume is reduced considerably by formation of a small gastric pouch (small stomach) that holds only 2-3 tablespoons of food. In addition, a ring with a small diameter is often placed at the junction between the stomach pouch and intestine to slow the rate that food leaves the pouch, causing one to feel ‘full’ for a longer period of time.

With the gastric bypass procedure, the part of the stomach that produces acid and digestive enzymes is bypassed (food no longer passes through), and the newly formed small gastric pouch produces negligible amounts of acid and digestive enzymes. Without stomach acid and digestive enzymes, certain foods are not adequately broken down to release their nutrient content.

The small stomach pouch also produces no intrinsic factor, an agent that must bind to vitamin B12 for its absorption from the gut into the body. The gastric bypass procedure, therefore, causes deficiencies in vitamin B12, the vitamin that assists in the metabolism of food (carbohydrate, fat, and protein), DNA replication and repair, nerve conductance and function, the formation of blood cells, and more.

The malabsorptive component of the surgery includes bypass of the upper portion of the intestines (the duodenum) along with a portion of the jejunum (the second major segment of the gut). Bypass of the duodenum causes malabsorption of, and therefore deficiencies in, iron, calcium, zinc, and folate. Other B-complex vitamins are also reduced with gastric bypass, both as a result of decreased absorption and to reduced nutrient intake and digestion. Furthermore, the gastric bypass procedure reduces fat absorption which may, consequently, cause deficiencies of fat-soluble vitamins, including vitamins D, E, K, and A.

Studies have shown that daily multivitamin and mineral supplements, at amounts close to the RDI (Recommended Daily Intake), correct most micronutrient deficiencies following gastric bypass surgery, with the exception of zinc, calcium, iron, folate, and vitamin B12. These vitamins and minerals generally require supplementation at amounts greater than the RDI.

Several studies have found that, even with supplementation, iron deficiencies occur in 30% to 60% of the gastric bypass population.  Iron deficiencies occur for males, as well as females, but are more common among pre-menopausal females.  Within the first two years following surgery, 30-40% of gastric bypass patients have been reported to suffer from anemia secondary to poor iron absorption.

Iron deficiencies may be prevented with iron taken at amounts given to women during pregnancy, ~40 mg. Iron as ferrous fumerate or chelated to amino acids are the most readily absorbable forms of supplemental iron. And, heme iron, obtained from eating meat, is far more readily absorbed by the gut than is non-heme iron from plants or supplemental sources.

Approximately 20% of the gastric bypass population is likely to develop folate deficiencies. Such deficiencies can be corrected or prevented by intake of supplemental folate at 800 to 1000 micro-grams (µg) per day or approximately 200% the RDI. 

Vitamin B12 deficiencies occur in up to 70% of patients, with as many as 30% of patients having such deficiency while on supplements that meet the B12 RDI.  As mentioned earlier, the small gastric pouch does not produce intrinsic factor necessary to bind B12 for its absorption out of the gut and into the body.

Studies have found that B12 deficiencies, for the majority of gastric bypass patients, can be prevented or effectively treated with B12 supplements in amounts that are high enough to cause passive diffusion of B12 across the gut in the absence of intrinsic factor. B12 supplemented at amounts far in excess of the RDI (as high as 100 to 350 micrograms) have been found to prevent B12 deficiencies in >95% of post-surgical gastric bypass patients.

Sublingual B12 (under the tongue) taken daily may also be effective in the prevention of B12 deficiencies since the vitamin is absorbed into the blood stream and does not need to bind to intrinsic factor for absorption. B12 shots taken daily or monthly are also effective in bypassing impaired B12 absorption and in preventing and treating B12 deficits.

Defects in folate and B12 may cause anemia (pernicious anemia), as well as elevated production of homocysteine and concomitant increased risk of cardiovascular disease. Symptoms of folate deficiency include: weakness, headache, palpitations, forgetfulness, hostility, irritability, paranoid behavior, apathy, sore tongue, gastrointestinal tract disturbances and diarrhea. 

B12 deficiencies may also cause gastrointestinal disorders, such as diarrhea, cramping, constipation, as well as palpitations, shortness of breath, and extreme fatigue. Neurological deficits secondary to B12 deficiencies include impaired bladder control, numbness, tingling of the extremities, moodiness, agitation, disorientation, insomnia, confusion, dimmed vision and even delusions and hallucinations.  Some of these neurological deficits caused by B12 deficiencies may be irreversible.

Calcium deficiencies occur following gastric bypass for several reasons.  First, the portion of the gut where calcium is actively absorbed (the duodenum) is bypassed by the surgical procedure. Secondly, there is insufficient acid produced by the small stomach pouch to provide enough acid in the gut for appropriate calcium absorption. Third, changes made in the mixing of food with pancreatic juices may alter vitamin D absorption. And, finally, some patients become lactose intolerant after surgery and avoid dairy products.

Low calcium is known to cause bone loss. Recent studies have also found that low calcium intake is associated with weight gain. Calcium supplements may, therefore, not only prevent bone loss but also assist in promoting weight loss and preventing weight regain following bariatric surgery.

Calcium supplements of 1200 mg to 2000 mg taken in 400-500 mg aliquots 3 times per day are recommended for individuals who have had gastric bypass surgery. Calcium citrate, rather than calcium carbonate, is more readily absorbed in the non-acidic environment of the gut of the gastric bypass patient. Absorption is further enhanced by calcium supplements that include vitamin D or magnesium.

The high risk for B12, folate, iron deficiencies following gastric bypass requires that the individual have periodic tests (annually) for blood levels of ferritin (iron), folate and B12.  Blood tests for measurement of blood calcium are unreliable. When blood calcium is low, the body ‘borrows’ calcium from bone and teeth so that levels may appear ‘normal’. Thus, it is wise for the gastric bypass patient to occasionally have a bone scan, a bone demineralization test, or some other test that can be used as a marker for low calcium.

Protein deficiencies are common with gastric bypass and occur secondary to: 1) low calorie intake, 2) avoidance of meat, 3) negligible acid and digestive enzymes produced by the stomach, and 4) reduced absorption of protein by the bypassed gut.  Low protein intake after surgery can cause muscle loss which, in turn, leads to a reduction in basal metabolic rate (reduced amount of calories burned at rest), interfering with maximal weight loss success. The heart is also a muscle and can lose tissue with severe protein deficiencies. For these reasons, protein supplements and high intake of protein is encouraged for all gastric bypass patients - and for life.

More and more patients in the United States are choosing the biliopancreatic diversion with the duodenal switch for weight loss surgery. The individual who has had the duodenal switch can eat normally because the portion of the stomach that produces digestive enzymes and acids is reduced but not bypassed. Weight loss with this procedure is caused primarily by malabsorption through bypass of a larger portion of the gut.

Possible nutrient problems following the duodenal switch which may occur without nutrient supplementation include the following: protein deficiencies, low levels of fat-soluble vitamins (A, E, D, K), low amounts of B-complex vitamins, low minerals and, in particular, calcium, iron, and folate deficiencies. Such deficiencies can lead to muscle and bone loss, anemia, neurological defects, high oxidative stress and associated risk for disease, and more. To avoid such nutrient deficits with the duodenal switch, high protein diets or protein supplements and daily vitamins and minerals are required for life.

In summary, nutrient deficiencies following the gastric bypass and duodenal switch are common and can lead to serious health consequences if left unattended. Increased intake of protein or protein supplementation is necessary long-term following these procedures. Vitamin and mineral supplements at RDI levels for most micronutrients, or greater than RDI for specific ones (calcium, iron, folate, zinc, B12), are required for life. Because nutrient deficiencies have very serious and often irreversible health consequences, periodic vitamin and mineral blood tests are necessary on a periodic basis, i.e. usually annually.