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Vitamin deficiencies “easily avoided”

Increased research and greater use of existing knowledge could prevent vitamin deficiencies
No standard protocol for changing dietary supplement regimen
​Erlen​d Aasheim

Vitamin deficiencies in bariatric patients could be easily prevented with more research and greater use of existing knowledge, according to a nutritional expert.

Nutrition expert Erlend Aasheim of the Department of Public Health and Primary Care, University of Cambridge, said that symptoms of vitamin deficiencies were often evident in bariatric patients, but should be easily avoided with careful observation and the use of dietary supplements.

The absorption of nutrients in bariatric patients is complex, said Aasheim. An operation may bypass the primary absorption point for a mineral in the GI tract, or factors can interact, and a deficiency in one nutrient can lead to deficiency in another.

Existing studies into malabsorption are methodologically problematic, for a number of reasons, said Aasheim. Populations with different characteristics and diets have been used, surgical methods vary, supplementation regimens and levels of adherence weren’t reported, and there is no standard protocol for changing the supplement regimen on review of blood tests. Results have accordingly differed substantially.

“It’s extremely difficult to make sense of these studies, in my opinion,” said Aasheim.

However, one study which Aasheim described as “one of the best” did provide evidence that a multivitamin is not sufficient for most patients to avoid malnutrition. 

The study gave 137 gastric bypass patients a single multivitamin each and monitored their nutrient levels at six-month intervals. Patients with low vitamin levels were given top-up supplements.

After two years, nearly all of the patients in the study were using supplements. By the end of the study, 80% of patients were deficient in vitamin B12, 60% were deficient in iron, 60% in calcium and vitamin D, and 45% in folic acid. 

Following this study, Aasheim recommended vitamin B12 as a baseline supplement, as most patients are going to become deficient without it.


In many cases, said Aasheim, supplementation and other effects can actually lead to increased nutrient levels in bariatric patients. This can be beneficial, as obese patients often have low vitamin levels before surgery. In a study looking at 110 obese patients before surgery, he found that 10-40% had deficient levels of vitamins B6, C, D, and E.

A recently published study showed a significant increase in levels of vitamins B6, folate, B12, A, and E adjusted for lipids, compared to increases in vitamin levels provided by lifestyle changes alone.

Wernicke’s Encephalopathy

Aasheim also encouraged doctors to be particularly careful to watch for Wernicke’s Encephalopathy [WE], which is caused by vitamin B1 (thiamine) deficiency. WE has symptoms including an unsteady gait, disturbed eye movements, and confusion and changes in behaviour. While treatment can reverse the symptoms, the condition is only completely reversible if treated quickly.

In a literature review that Aasheim carried out, he found that around one in 500 patients who undergo biliopancreatic diversion subsequently develop WE. “It’s potentially lower after gastric bypass, but we don’t know that,” he said.

Aasheim hypothesised that WE could be brought on in patients who suffer from frequent vomiting, saying that it occurred in 90% of the cases in his study, and generally lasted for around three weeks.

“The body can become deficient in thiamine in 18-20 days. It fits very well with the duration of vomiting,” said Aasheim.

In about 20% of cases, the patient had received intravenous glucose, which can also trigger thiamine deficiency.

Other symptoms that indicate WE include eye movement signs (70% of cases), mental status changes (64%), leg neuropathy (60%), and gait ataxia (57%).

Aasheim described investigating to confirm a suspected diagnosis as “a double-edged sword”, as delaying treatment can harm the patient.

“In about 50% of cases in the review had some form of lasting permanent neurological damage,” said Aasheim. “These people can end up in wheelchairs and in the nursing home. Two or three of them died, so it’s extremely severe.”

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