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Vitamin B12 Basics

Bailey Bariatrics dietitian Rene Norman, RD/LD, joins us on the blog today to explain how vitamin B12 is absorbed by our body and why that is of special consideration for anyone who has had bariatric weight loss surgery.

Vitamin B12 does a lot of work - protecting nerves, helping to release energy from our foods and working with folate to produce healthy red blood cells and keep homocysteine (an inflammation molecule) in check. Symptoms of a B12 deficiency include fatigue, tingling or numbness in your extremities, weakness, vision changes, abnormal gait, difficulty concentrating, memory loss, a smooth tongue, hypersensitivity in your skin, depression, behavioral changes, shortness of breath and pale skin. Pernicious anemia develops when a B12 deficiency is prolonged. 

How our bodies absorb B12 is a complex process. Our stomach provides acid and pepsin to release B12 from our food. The B12 then binds to a molecule called intrinsic factor as it enters the duodenum, which is the small intestine area right after the stomach. The intrinsic factor stays bound to the B12 until it reaches the ileum, which is the last part of the small intestine. B12 is released from the intrinsic factor and then absorbed through the ileum.

Food-based B12 is found primarily in meats (beef, pork, chicken, turkey, fish, shellfish and game meats) and eggs. Dairy foods contribute some, but not as much as meat-based foods. 

You may have adequate stores of B12 prior to surgery if you are getting most of your protein from meats and eggs. When people suddenly convert to strict vegetarian eating, they may have a couple of years of B12 stored. However, they will need to be monitored through lab work to prevent a B12 deficiency. 

Having bariatric surgery puts you at a higher risk of B12 deficiency due to a reduced stomach pouch. First, you can’t eat as much, which decreases food-based B12 sources.  Second, you also reduce the ability to release B12 from your food, because you have less stomach acid available. Medications that block stomach acid can further reduce B12 absorption. These are common medications used before and after surgery. For patients that have had RNY gastric bypass, any food-based B12 is not able to bind with intrinsic factor, because the ileum is bypassed. 

Getting regular lab work after surgery is essential to keep your B12 status in good shape. B12 is available by prescription or in an over-the-counter supplement. Prescription forms of B12 include injections or the Nascobal nasal spray B12. You can also try over-the-counter, sublingual forms of B12. Sublingual means under the tongue, which allows the B12 to be directly absorbed from your mouth and gets into your bloodstream fairly quickly. You can find over-the-counter, sublingual liquid drops or tablets in your pharmacy. Look for B12 supplements that have 350 to 500 mcg per dose.