Who should get tested for vitamin B12 (cobalamin) deficiency and which is the best test to use: serum B12, methylmalonic acid (MMA), or holotranscobalamin levels?
Image thanks to Bobjgalindo via Wikimedia Commons.
Should people who eat plant-based diets be tested for vitamin B12 deficiency? In my opinion, medical tests should only be ordered if the results, one way or the other, are going to change what you do. If your test came backing showing your B12 levels were low, what would you do? You'd insure a regular, reliable source of vitamin B12. If your tests came back showing your levels were OK, what would you do? You'd ensure a regular, reliable source of B12 because you wouldn't want them to become not-OK.
So, if it's not going to matter either way, I wouldn't worry about it: with two exceptions. I recommend anyone with unexplained neurological, psychiatric, or developmental symptoms be tested, especially in infants, toddlers, vegans, and anyone over 50; and, out of an abundance of caution, I've always tested all my pregnant and breast-feeding vegan patients, just because the consequences of deficiency are so potentially devastating.
Better than getting a serum B12 level drawn, though, which most doctors do, a methylmalonic acid level is a superior test for B12 deficiency, which can be blood or urine. You can just pee in a cup for it.
Here's why measuring MMA levels is better. About 50 people started eating vegan. Within a few years half became B12-deficient. But look at their B12 levels. All these vegans had functional B12 deficiency despite normal levels of B12 in their blood, showing that MMA is a more effective test.
Now their has been a case report published of someone with apparent B12 deficiency who had normal B12 and MMA levels. So since we're always looking for a better test, it looks like HoloTC is it, measuring Holotranscobalamin levels, shown to be more sensitive and specific, meaning fewer false negatives and false positives. If your level is under 20 you start treatment. If it's over 30, you can be pretty sure you're OK. And if it's in the middle, you follow up with a second-line test.
If you are deficient, you can be treated with a ruby-red mad-scientist-looking injection of B12. The color is from the cobalt in the molecule. But one of medicine's best-kept secrets is the efficacious use of high-dose oral B12 -- safer, cheaper. 2000 microgram supplements every day for two weeks should do it, before having patients starting or resuming their regular, reliable regimen of B12.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is transcript contributed by Bruce A. Hamilton.
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This concludes our five-part video series on B12 this week. Please leave any questions you may have below. If you're new to the issue, Vegan B12 Deficiency: Putting It into Perspective and Safest Source of B12 are good places to start. The consequences of B12 deficiency can be grave (see Inverted Rabbit Sign), but getting enough is easy: B12 can be taken weekly (see Cheapest Source of Vitamin B12) or daily (see Daily Source of Vitamin B12). See my full recommendations and check out the other 1000+ topics I cover here at NutritionFacts.org.