Vitamin B12, or cobalamin, is a necessary ingredient in chemical reactions that help our cells function. It is found in mitochondria, one of the oldest forms of life, and is produced by bacteria, usually in animal-based products.
Common sources of cobalamin for humans include:
Meat — Both red and white meat are good sources. Organs rich in B12 include the liver and kidneys.
Fish and Shellfish: Salmon, trout, tuna and sardines, as well as clams.
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Dairy Products: Milk, cheese and yogurt.
Eggs.
For those who follow a vegan diet, natural sources of vitamin B12 are scarce and not usually found in plant foods unless contaminated by bacteria. However, fortified foods such as plant milk, soy products and cereals can contain sufficient vitamins.
Vitamin B12 deficiency is common and can lead to anemia, mental status or psychiatric changes and nerve function abnormalities. Patients often complain of neuropathy symptoms such as weakness.
Upon evaluation, these patients may also demonstrate proprioception changes, such as an inability to sense position or vibrations and increased spasticity or muscle tightness. Deficiencies of cobalamin have also led to bone marrow effects, leading to a reduction of any of the three cell lines: leukocytes (white blood cells), erythrocytes (red blood cells) and thrombocytes (platelets).
After vitamin B12 is ingested from the diet, it is absorbed in the stomach and small intestine. Through various chemical reactions, the vitamin is taken up by the cells in the small intestine for further processing. During this pathway to the last portion of the small intestine, many barriers can cause disease, prohibiting normal absorption and uptake by cells.
Nutritional deficiencies in the diet are the most common cause of low vitamin levels. Stomach surgeries, such as gastric resection, which may be performed for severe ulcers, or bariatric surgery for weight loss, can lead to reduced absorption. Bariatric surgeries can reduce several vitamins that must be accounted for in post-surgery dietary plans.
Common drugs leading to vitamin B12 deficiency include metformin, which is a first-line medicine for newly diagnosed diabetics. Patients are often on metformin for years. Up to one-third of patients on metformin will develop vitamin B12 deficiency and need screening.
Proton pump inhibitors, a favorite for patients with GERD or reflux, can also inhibit proper B12 absorption by reducing gastric acid production. Examples of proton pump inhibitors include omeprazole (Prilosec), esomeprazole (Nexium) and pantoprazole (Protonix).
Chronic pancreatitis can limit absorption.
Finally, inflammatory bowel diseases, such as Crohn’s and Ulcerative Colitis, limit gastric and intestinal absorption of many vitamins by the ongoing gut inflammation.
Screening for vitamin B12 deficiency usually takes place once risk factors are identified. Neurologic symptoms such as those above and new anemia are strong reasons to test for deficiency. As several factors can cause anemia, simply having anemia alone is not specific to vitamin B12. Iron deficiency remains the leading cause of anemia and will be tested. Testing can be performed on a blood sample.
Simply ingesting vitamin B12 in pill form can alleviate the deficiency for most patients. Doses are administered either daily or monthly. Vitamin B12 is available in two formulations. Patients are usually started on pills. However, those who are unable to absorb sufficient amounts of B12 from pills or their diet will need injections. Depending on the nature of your cobalamin deficiency, your physician will determine which formulation you need.
As stated above, the symptoms described can occur in many diseases. If you are concerned about vitamin B12 deficiency, seek an appointment with your doctor to determine your risk of having this deficiency.
Dr. Naznin Jamal is a Jefferson Regional Medical Center hospitalist.