B12 deficiency is surprisingly common, even in people who eat well, take good care of themselves, and sometimes even in people who make the effort to take B12. Oddly, more and more people seem to be showing up with what looks like good B12 levels in their blood, or even like too much B12, but with symptoms of deficiency. What is happening here? Let’s look at what happens with B12 in your body.
There are four steps to good B12 levels:
- Get some in your diet or supplements. If you don’t eat it, then your levels probably aren’t going to be great. 🙂
- Absorb it. Many of us have trouble with this part.
- Transport it. B12 doesn’t float freely in the blood, it has to be bound to proteins. This can be tricky too.
- Pull it into cells for use. If it just keeps floating around in your blood then it doesn’t actually do you any good.
Let’s look at each of these steps and see what is actually happening.
Step 1: Getting B12 from Food and Supplements
Food sources of B12, sorry vegans, are mostly animal in origin. Fruits have some, and grains are listed only because they are fortified artificially – on their own they aren’t a great source. Clams and beef liver top the list and it’s rounded out with a variety of fish, meats and dairy products. Below is a picture, from enutritionguide.com showing some of the best sources. The link goes to the full article for more detailed information.
Supplements largely come in three varieties.
- Methylcobalamin is technically the most active form and we don’t have to methylate it (good for some of us mutants) in order to use it. It metabolizes rapidly and tends to be difficult to tolerate, ironically, for some mutants because it effectively floods the system. If you’re a mutant you might want to read more about that problem here.
- Hydroxycobalamin is slower to metabolize and generally my preference for people with MTHFR or MTRR mutations, although there is a lot of debate about this in the field.
- Cyanocobalamin is the least expensive to manufacture or buy and the most widely available. It requires conversion to the active form so may not work as effectively for some people.
There are also different routes of administration.
- Oral (swallowed) is typically the form present in your multivitamin because most multivitamins have to be swallowed, even if they are in a liquid or chewable. According to the NIH, approximately 58% of a 1 mg oral dose of B12 is absorbed, but absorption decreases as dose increases because the capacity of your intrinsic factor (we’ll get to it in a minute) is exceeded.
- Sublingual, or under-the-tongue forms, seem to absorb slightly better and change serum levels slightly more according to this article from the British Journal of Clinical Pharmacology.
- Intramuscular, or injected, bypasses your normal absorption completely and enters the bloodstream directly so this is the best format for anyone who suspects an absorption issue.
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