Vitamin B 12 – Deficiency

Deficiencies in micronutrients are very common in patients with obesity even before surgery and persist after surgery Vitamin B 12 is a water-soluble B vitamin usually acquired from the diet. The body has a 12-18 month storage of Vitamin B12. Vitamin B 12 absorption is a complex process. Healthy adults absorb approximately ½ of their ingested vitamin B 12. This is affected by many factors. Secreted gastric acid and pepsin in the stomach allow Vitamin B12 to dissociate from proteins in food. B 12 is then bound to R proteins or haptocorrins (vitamin B12 binding protein) which carry Vitamin B 12 into the intestines. R. Proteins are then broken down in the small intestine and release vitamin B 12 where it bind to intrinsic factor which is secreted by parietal cells in the stomach. This intrinsic factor-vitamin B 12 complex is then transported into enterocytes (these are simple columnar epithelial cells, which are body tissues) and enters the circulation where it is bound by a protein known as transcobalamin II. Any interruption is these steps can lead to impaired vitamin B12 absorption.

We see deficienciesin malabsorptive procedures as Gastric Bypass as a result of changes in acid secretion leading to impaired absorption. Sleeve gastrectomy produces neurohormonal changes, reduced acid production and significantly reduced intrinsic factor, therefore, directly affecting iron and B12 absorption. Deficiency is seen more commonly at two years or greater post-surgery. Therefore, yearly laboratory monitoring is essential. Further, women with low B12 levels may have a falsely abnormal Pap smear. This is due to the way B12 affects the way epithelial cells look.

Symptoms of Vitamin B 12 deficiency:

    1. Diarrhea or constipation
    2. Fatigue, lack of energy or light – headedness when standing up or with exertion
    3. Loss of appetite
    4. Pale skin
    5. Difficulty with concentration
    6. Shortness of breath, particularly during exercise
    7. Swollen, red tongue or bleeding gums.

Long time Deficiency can affect nerve function and cause damages. This may be permanent if treatment is not started within 6 months of the onset of symptoms. These symptoms include:

    1. Confusion or change in mental status
    2. Depression
    3. Loss of balance
    4. Numbness and tingling of hands and feet
    5. Problems with reflexes

Treatment goals are to restore normal vitamin B 12 levels. This can include B12 injections weekly and then monthly for several months. Alternatively, high dose, oral vitamin B12 works well and injections are not needed.

For a quick summary, see table below:

FunctionDeficiencyFood Sources
Formation of mature red blood cells

Synthesis of DNA, RNA

Requires intrinsic factor from stomach for absorption
Pernicious anemia – lack of intrinsic factor and/or after gastrectomy

Macrocytic anemia: neurologic degeneration, pallor
Animal foods only: milk, eggs, meat, poultry, fish

Image of upper body with a description of how B-12 supports body function.

Image of normal red blood cell count and an image of anemic red blood cell count having significantly fewer red blood cell after vitamin B-12 Deficiency

Signs of Vitamin B 12 deficiency below:

Image of fingernails with ridges and yellow discoloration with Vitamin B-12 Deficiency.

Vitamin B-12 Deficiency and an image of the tongue with white patches.


Craggs-Dino, L. M. (2013). Approaches to providing Nutritional guidance After Vertical sleeve Gastrectomy: Do we Consider the VSG as Purely Restrictive or Something More. Bariatric Times, 24-26.

Dawson-Hughes, M. B. (2013). Treatment of vitamin D deficiency in adults. UpToDate, 1.

Kushner, M. R., & Cummings, M. S. (2013). Overview of medical management of patients after bariatric surgery. UptoDate, 1-36.

NIH National Insitutes of Health. (1997). Anemia – B12 deficiency.

Pharmacist’s Letter/Prescriber’s Letter. (2008, March). Prevention and Treatment of Vitamin D deficiency. p. Vol. 24.

Prescriber’s Letter. (2011). Treatment of Vitamin B 12 Deficiency. Prescriber’s Letter, 18(18):270811.

…..more next month!!

Michel Gunn

Michel Gunn