The most recent Vegetarian Journal takes a look at recent scientific literature on veggie diets. One topic covered is taking Vitamin B12 daily or weekly. Here’s our write-up on this study:

Vitamin B12 recommendations from
many vegan groups, including The Vegetarian Resource Group, are based on
calculating how much vitamin B12 is likely to be absorbed from supplements
containing different amounts of vitamin B12. For example, in 2015 we said,
“About 5% of the vitamin B12 in a supplement containing 25 mcg of vitamin
B12 is absorbed. A lesser amount, 1% or less of the vitamin B12 in a supplement
containing more than 100 micrograms of vitamin B12, is absorbed.”1
A recent study examines whether these theoretical absorption rates actually
apply in vegans and non-vegan vegetarians.

In this study,2 36
vegetarian (including vegan) adults who were marginally deficient in vitamin
B12 based on their blood vitamin B12 levels, were randomly divided into two
groups. During the 12 week study period, one group took 50 micrograms of
vitamin B12 daily and the other group took 2,000 micrograms of vitamin B12 once
a week. Blood vitamin B12 was rechecked throughout the 12 weeks. Both groups’
blood vitamin B12 levels improved as did other indicators of vitamin B12 status
so that, at the end of the study, they were no longer considered to be
deficient. These results support recommendations to take vitamin B12
supplements either daily if you are using a lower dose (25-100 micrograms) or
weekly for a higher dose of 2000 micrograms. One advantage of using a lower
dose daily could be that you’re less likely to forget to take your supplement
if it is part of your daily routine. On the other hand, taking a larger dose
one day each week, perhaps first thing Monday morning, may be easier for some
people to remember to do. In any case, it’s important to have a regular source
of vitamin B12, whether fortified food or supplement.

1 Mangels R. 2015. Nutrition
Hotline. Vegetarian Journal.
Issue 4.

2 Del Bo C, Riso P, Gardana C, et
al. 2018. Effect of two different sublingual dosages of vitamin B12 on
cobalamin nutritional status in vegans and vegetarians with a marginal
deficiency: A randomized controlled trial. Clin Nutr.
pii: S0261-5614(18)30071-2. [Epub ahead of print].

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