How Nutritional Deficiencies After Bariatric Surgery Can Cause Neurological Disorders
How Nutritional Deficiencies After Bariatric Surgery Can Cause Neurological Disorders 

With bariatric surgery comes the risk of developing nutritional deficiencies. Bariatric surgery alters the anatomy and digestive tract, playing a significant role in vitamin and nutrient levels post-operatively. These nutritional deficiencies after bariatric surgery can cause neurological disorders if left untreated. 

A nutritional deficiency is most commonly a result of malnutrition caused by not eating enough (nutritious) food or developing an eating disorder. However, after bariatric surgery, malnutrition is almost always a result of the procedure itself. 

The gastric bypass and the duodenal switch are both malabsorptive procedures, meaning you cannot absorb all the nutrients consumed. Combined with the effects of eating fewer calories due to the restrictive nature of all bariatric procedures, including the gastric sleeve, patients have a heightened risk of developing nutritional deficiencies after bariatric surgery. 

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Nutritional Deficiencies after Bariatric Surgery

To counteract the negative impact of nutritional deficiencies after bariatric surgery, surgeons will require their patients to take vitamins (for life) after their procedure. Yet still, some nutritional deficiencies after bariatric surgery are more likely to cause neurological disorders, including vitamins B12, folate, copper, vitamin D, and vitamin E. 

Vitamin B12

One of the most common vitamin deficiencies in post-bariatric patients is vitamin B12. However, a B12 deficiency may not be recognizable for several years after surgery due to sufficient liver stores. 

Vitamin B12 comes from animal-based foods and is used to help make DNA, red blood cells, and nerve cells. A B12 deficiency left untreated long-term could lead to cognitive impairment, nerve problems such as numbness or muscle weakness, vision loss, mood disorders, and dementia. 

Bariatric surgeons recommend that you have your B12 levels checked regularly, especially after month six, to ensure optimal levels post-operatively. The good news is that if this nutritional deficiency is caught early enough, it can be treatable, with symptoms being reversible. 


Copper is another common nutritional deficiency after bariatric surgery due to the malabsorptive nature of the procedures. Most of the copper we consume is absorbed in the stomach and small intestines, bypassed in many bariatric procedures. 

A copper deficiency is very similar to a vitamin B12 deficiency in that it attacks your memory, sensory nerves, vision, and movement. If you are diagnosed with a copper deficiency, your healthcare provider will recommend taking a copper supplement for about 4 to 12 weeks to correct the levels. 


Although a folate deficiency after bariatric surgery is rare, occurring in less than 1% of patients, it is still something to watch out for, especially for women who are pregnant or considering pregnancy. Low folate levels in pregnant women can cause fetal brain and spinal malformations by inhibiting the proper development of the embryonic neural tube. 

A folate deficiency can cause peripheral neuropathy in adults, characterized by weakness and numbness in the hands and feet. To correct a folate deficiency, we recommend eating green leafy vegetables and citrus fruits and supplementing with an oral folic acid. However, it is important to note that "folate supplementation can mask an underlying B12 deficiency, leading to the progression of neurological damage."

Vitamin D

Vitamin D is essential for promoting calcium absorption and balance, immunity, and cellular function. Vitamin D is found in very few foods but is instead absorbed from the sun through the skin. Patients who are vitamin D deficient may experience bone or muscle pain and chronic cramping or body aches. 

Low vitamin D levels have also been linked to hypocalcemia, characterized as having deficient calcium in the blood. Hypocalcemia can cause neurological disorders such as confusion, memory loss, depression, and hallucinations. The recommended dosage after bariatric surgery is about 1500 mg of calcium per day and 3000 IU of vitamin D a day. 

Vitamin E

Vitamin E deficiencies are commonly seen in patients 6 to 12 months after surgery, but it has also been evident in patients 5 to 10 years post-op. After bariatric surgery, symptoms of a vitamin E deficiency include:

  • Muscle weakness and tingling.
  • Eye movement abnormalities.
  • Vision impairment.
  • Cerebellar ataxia (loss of balance and coordination).
  • Some sensory loss. 

To fix a vitamin E deficiency, we recommend increasing your intake of seeds and grains and taking an oral vitamin E supplement. 

Conclusion on Nutritional Deficiencies and Neurological Disorders

Nutritional deficiencies after bariatric surgery are prevalent and, if left untreated, may cause neurological disorders. In many cases, proper diagnosis and treatment can prevent and reverse any damage to the brain and nerves. It is important to continue to follow up with your bariatric care team on a continuous basis after bariatric surgery to ensure you maintain optimal vitamin levels. Taking the recommended supplements will also help prevent any serious health or neurological disorders post-operatively. 

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Mike Blaney, MD
Dr. Mike Blaney is a board-certified surgeon with over 20 years of experience in general and bariatric surgery. He is the founding physician of Live Healthy MD which has since been acquired by HCA and now operates under the name Doctors Specialists – Bariatrics and Surgical. Dr. Blaney is co-founder and CEO of Bariatric Centers of America and is fueled by a passion to cure the disease of obesity.
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