The In’s and Out’s of Vitamin B12
As many of you know, I host a B12 Happy Hour every Friday. I offer discounted vitamin B12 shots that are administered intramuscularly. Vitamin B12 deficiency is common, mainly due to limited dietary intake of animal foods or from absorption issues (1). People come in for all sorts of reasons: to support their immunity, provide an energy boost, address deficiency found on labs, as weight loss support and much more. This week I’ll tell you what exactly vitamin B12 does in the body, symptoms that would warrant B12 therapy and when/how to test your levels.
What is Vitamin B12?
Vitamin B12, or cobalamin, is a nutrient that helps keep the body’s nerve and blood cells healthy. It also helps make DNA, our cellular genetic material. B12 is needed to prevent anemia that causes people to feel tired and weak. Our bodies cannot make vitamin B12 so we have to get it from food. In order for B12 to be absorbed, we first need hydrochloric acid in the stomach to unbind B12 from food, then the B12 has to bind with a protein in the stomach called ‘intrinsic factor’ so it can be absorbed (2).
The most common symptom of B12 deficiency is fatigue with possible numbness and tingling due to B12’s role protecting the myelin sheath, the outer protective layer of nerves (3).
Foods that contain B12 are:
Beef liver and clams (They are the highest in B12)
Fish, meat, poultry, eggs, milk and other dairy products
Some breakfast cereals, nutritional yeasts and other fortified foods
When should you get screened?
Testing your levels is warranted if you have one or more of the following risk factors:
you’ve had a gastric or bowel surgery
have inflammatory bowel disease
have used metformin for more than four months
use proton pump inhibitors or histamine blockers for more than 12 months
are vegan, vegetarian, or older than 75 years old (4).
It is recommended that everyone over the age of 50 supplement or eat fortified foods5.
How To Test for B12 deficiency?
There is no gold standard for testing B12 levels. I’ve recently learned a couple of pearls that I will be implementing clinically ASAP. First, completely abstain from any supplements containing B vitamins for seven days prior to the draw. Second, this is a 12-hour fasting draw with nothing but water allowed. We can test a serum B12, and if these levels are low, we can be confident there is a deficiency. Methylmalonic acid and homocysteine are other key biomarkers for functional B12 deficiency.
Who Should Supplement?
It is most ideal to know your B12 status so that treatment can be customized to your body. With that being said, vitamin B12 is water soluble, meaning you will pee out what your cells don’t use making over supplementation unlikely. No toxicity of B12 has been identified, even when administered intramuscularly at 300-3000 times the recommended dietary allowance (5).