10 basic Vitamin B12 facts, on B12 dosage, B12 supplements, B12 absorption, and sources of Vitamin B12 for vegan nutrition.

Questions About Vitamin B12:

I see that the Vitamin B-12 RDA is 2.4 mcg and the Daily Value for B- 12 is 6 mcg, and some vegan sources say take 10 mcg in a supplement.

Then I see the NIH ^[1] site has this information regarding B-12: “… only about 10 mcg of a 500 mcg oral supplement is actually absorbed in healthy people…”. I do not want to take a mega dose that I find in supplements, but I wonder, do you have to in order to absorb the small amount needed?

Centrum brand multivitamins has 25 mcg of B -12. Is that enough to get absorbed?

What about eating actual food that has 3.4 mcg to 6 mcg, can you assume you are absorbing the RDA amount?

I saw on a vegan site you could take 10 mcg as a supplement . Is that enough to be absorbed? - A.J.

Savvy Vegetarian Advice:

Hi A.J. It’s all a bit murky what dosage of B12 is best, and there are a few factors which come into play. Probably you’d be fine with the 25 mcg Centrum supplement if that’s the one you want to take, but of course, I can’t guarantee that.

To clear up any confusion, and set your mind at rest about B12, here are the facts according to my limited understanding (see medical disclaimer below):

10 Vitamin B12 Basics:

1. Your body will harmlessly excrete whatever Vitamin B12 it doesn’t use from supplements. And you pay about as much for a high dose as for a low dose. So the exact dosage isn’t so important.

2. Our bodies can store Vitamin B12, for various lengths of time, depending on age, physical condition and other factors. But it’s best not to rely on that. At times of high stress, illness, pregnancy etc, the body’s stores of B12 can be used up very quickly.

3. I’m not sure why almost all of the Vitamin B12 supplements have huge doses. It could be that it’s difficult to package tiny doses which aren’t enough to fit on the head of a pin, but I doubt that.

4. It’s possible that massive doses of Vitamin B12 are meant as insurance that you’ll absorb what you need, but I’m sceptical about that too.

5. The RDA’s for all vitamins and minerals are set high for safety’s sake. 10 mcg of B12 is about 4 times what your body actually needs to use on average, per day.

6. Critical factors in B12 absorption are the presence of an enzyme called intrinsic factor in the intestines, and villi, tiny hairs in the intestinal walls. Even if you take in large amounts of B12 in your food, or supplements, if you can’t absorb it well, you may still become deficient. That’s more common in people over 50, but it’s a good idea for everybody, not just vegetarians or vegans, to get B12 levels tested with every physical checkup.

7. One of the best ways to get B12 is in animal products where it comes with the food (grows on it, actually). Other good sources for vegans, are B12 enriched foods such as non-dairy milk and yogurt, and nutritional yeast. Read labels before you buy to make sure that Vitamin B12 is included in enriched foods.

8. If you feel you need to take a separate B12 supplement, or your health professional recommends it, the best form is sublinglual tabs or spray of Methylcobalamin B12 (better absorbed than Cobalamin, which the body must first convert to Methylcobalamin).

9. Take a B12 supplement at least several times a week in addition to the other sources in your diet, preferably with food.

10. It’s better to be safe than sorry, because a Vitamin B12 deficiency can result in permanent brain damage, hearing loss, nerve damage and so on. Experts on vegan nutrition, such as Vesanto Melina and Brenda Davis (co-authors of the nutrition reference book Becoming Vegetarian ^[2]), recommend regular B12 supplements for vegetarians and vegans.

Medical Disclaimer: Any changes that you make to your diet, and the results of those changes, are your decision and responsibility. I do not claim to be a health care professional, dietitian, or nutritionist. Savvy Vegetarian does not treat, or recommend treatment, for any illness or health condition - Judith Kingsbury, Savvy Vegetarian

More Vitamin B12 Facts:

Vegetarians & Vegans, Are You Getting Enough Vitamin B12? ^[3]
Is Your Brain B12 Deficient? ^[4]

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^[6]Low Energy Vegan - Can Vitamins Cause Deficiencies? ^[6]

^[7]Vegetarian has Hypothyroidism, B12 Deficiency ^[7]