Vitamin deficiencies after bariatric surgery


Bariatric surgery can cause vitamin defi­ciencies in one of two ways: by reducing food intake or by causing malabsorption of vitamins. Sleeve gastrectomy is an example of the first way. Sleeve gastrectomies reduce stomach size, which reduces appetite and means the patient’s food intake decreases. This in turn means a reduced vitamin intake, so the patient ingests less vitamins than they did before surgery. Patients who already eat a diet low in vitamins are at more risk of vi­tamin deficiencies. This type of diet includes such as extrinsic sugar, potato chips, pro­cessed meats, cream, butter and soft drinks. The patient may have to change their diet as well as take vitamin supplements. The second way bariatric surgery causes vitamin deficiencies is malabsorption. Malabsorp­tion of food is actually the aim of intestinal bypasses. It causes weight loss because the body absorbs less calories than before sur­gery. The risk of vitamin deficiencies is ac­tually higher in procedures involving an in­testinal bypass. This means that procedures like sleeve gastrectomy cause less vitamin deficiencies, because they leave the intes­tine unaffected.

The main vitamin deficiencies that occur in postoperative patients are vitamin B12, vitamin D, and fat-soluble vitamins. These deficiencies are described in more detail below.

The first vitamin deficiency this review will discuss is vitamin B12 (cobalamin). The cause of vitamin B12 deficiency in post-surgery patients is decreased stomach acid. Stomach acid helps release vitamin B12 from food, but bariatric surgery limits this function by weakening the stomach’s acidic environment. This means vitamin B12 defi­ciencies are common after bariatric surgery. According to a study in 1986, 33% of pa­tients have a vitamin B12 deficiency after roux -en-Y gastric bypass.

However, the risk of B12 deficiency de­pends greatly on the type of bariatric sur­gery.

An additional finding was that patients developed B12 deficiencies even though they were supposed to take a daily supple­ment. So why did these patients still develop deficiencies? Perhaps the reason was that many patients did not actually take their supplements. Dolan et al. found that a fifth of patients did not take vitamin supplements, even though they had vitamin deficiencies Therefore, physicians should regularly as­sess post-surgery patients for compliance with vitamins supplementation.. Levels be­low <300pg/ml are subnormal for vitamin B12.

Another common deficiency after bari­atric surgery is vitamin D deficiency. The researchers analysed 355 obese patients who had undergone a sleeve gastrectomy or roux-en-y gastric bypass. They found that four years after surgery, the 44% of sleeve gastrectomy patients and 51% of roux-en-y gastric bypass patients had a vitamin D deficiency. The next most common vitamin deficiency was for vitamin B-6; 4-17% of pa­tients had a deficiency in B-6. Another study found that 51% of patients had vitamin D deficiency after a distal roux-en-y gastric by­pass. These studies demonstrate the wide­spread prevalence of vitamin D deficiencies in post-surgery patients. This is One of Vita­min D’s main roles is to promote the absorp­tion of calcium by the intestines. It also helps regulate cells and the immune system. Phy­sicians should ensure that patients do not fall below the serum 25(OH) vitamin D range of 20ng/ml..


Deficiencies of the fat-soluble vitamins (A, E and K) are also common after bariatric surgery. They are particularly common after biliopancreatic diversions with duodenal switch . One study measured the serum level of fat-soluble vitamins in 170 patients, four years after their biliopancreatic diversion surgery. The study found that occurrence of vitamin E did not increase significantly af­ter the surgery. However, the incidence of vitamin K deficiency increased by 68% af­ter surgery, and the incidence of vitamin A deficiency increased by 69%.These findings clearly demonstrate the need for long-term nutritional monitoring of these vitamins. Physicians should regularly test post-surgery patients for vitamin A, E and K deficiencies.


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