Causes of B12 Deficiency
Inadequate intake (common in vegetarians and vegans)
Intestinal malabsorption
Pernicious Anemia (affecting 2 percent of people over 60 years old) is an autoimmune condition that leads to destruction of Intrinsic Factor (IF)-producing parietal cells, or antibodies to IF itself
Atrophic gastritis (affecting 10 to 30 percent of people over 60 years old) which is often caused by H. pylori infection in the elderly
Pancreatic enzyme insufficiency
Alcoholism which reduces absorption of B12 in the terminal Ileum
Who is at risk for B12 deficiency?
Vegetarians and vegans (B12 is only found in animal products)
Elderly
Patients with long-term use of proton pump inhibitors
Patients with digestive disorders that lead to malabsorption
Disorders associated with low stomach acid, Celiac disease, Crohn’s disease, SIBO, and other GI conditions
Women with frequent miscarriages or infertility (this suggests probable B12 deficiency BUT the cause must still be investigated)
Those with genetic polymorphisms affecting B12 assimilation and metabolism
Patients with long-term use of Metformin
Symptoms of B12 deficiency
Weakness
Fatigue
Strange sensations
Numbness, or tingling in the hands, legs, or feet
Difficulty walking (staggering, balance problems)
A swollen, inflamed tongue
Yellowed skin (jaundice)
Difficulty thinking and reasoning (cognitive difficulties), or memory loss
Paranoia or hallucinations may be seen in severe cases (rarely)
More advanced cases will present themselves in the form of anemia with associated symptoms. Of note, B12 or folate deficiency anemia is associated with macrocytosis, or large red blood cells measured as a high mean corpuscular volume (MCV)
Recommended daily intake of B12
For people with normal absorption, we recommend daily intake of 17.6 mcg. This was the daily intake of our hunter-gatherer ancestors.
For people with impaired absorption, we recommend increasing daily intake to 150 to 200 mcg. This will likely require supplementation.
Foods highest in B12
FOOD AMOUNT (mcg per 100g)
- Clam 99
- Lamb liver 90
- Beef liver 83
- Duck liver 54
- Oyster 35
- Pork liver 26
- Caviar 20
- Mackerel 19
- Herring 19
- Chicken liver 17
- Mussel 12
- Crab 11
- Sardine 9
- Salmon 6
Muscle meats do contain B12, but the amount is significantly less than organ meats.
Plant foods do not contain true B12, but rather contain cobamides, which block the absorption of B12. This is why vegetarians and vegans must supplement in order to obtain adequate B12.
Supplementing with B12
B12 supplements should ideally contain all three forms of natural B12 (methylcobalamin, adenosylcobalamin, and hydroxycobalamin), and not contain cyanocobalamin, a synthetic form of B12.
Betaine HCl may be added to increase absorption since it increases stomach acid (only in the absence of gastric ulcers and if not taking NSAIDs).
Ask your clinician to re-test your B12 levels after 60 days of supplementation in order to confirm that your levels are improving. Treatment ranges from two months to ongoing, dependent on the cause of deficiency (I.E. patients with pernicious anemia will likely need to supplement for life).
