In my last video I touched on how the usual strategy of megadosing vitamin B12 may not
be as 100% safe as we once thought, and why I now take a more conservative dose of cyanocobalamin.
But in that video I didn't go into specifics on dosing or why I recommend this form of
the vitamin and I've had a few requests to explore this in more detail, so today we'll
be looking at dose.
I just want to qualify this first of all by saying that high-dose supplementation is still
the norm and is a perfectly viable strategy and I'm happy to continue recommending this
approach if you want to be 100% sure you're getting enough.
These new recommendations are to fully dial-in your regimen to also reduce that potential
increased cancer risk that has recently been associated with high-dose B12, whilst still
ensuring a high probability of adequacy.
The purpose of high-dose supplements is to bypass the specific B12 absorption mechanism,
since 1-2% of a dose can be absorbed by passive diffusion even if a person's specific absorption
isn't working properly.
With this in mind, if you fall into this group it's important to continue with the regimen
prescribed by your health care provider.
Failing specific absorption is very common as we age and with the use of certain medications.
But what if you don't have any known absorption issues?
Why don't there seem to be any supplements that provide only 100% of the RDA of B12 alone?
Even people with normal absorption can benefit from having a higher dose than the RDA - but
I would argue that it doesn't need to be on the order of thousands of micrograms per day
like we see with so many supplements.
To understand why we're going to look at three examples.
Remember that regardless of what B12 supplementation strategy you go for, it's important to get
your levels checked every so often along with your usual blood work to make sure you're
getting enough.
Check out my last video for more on testing status.
The RDA set by the National Academy of Medicine is 2.4 μg per day.
As I explained in my last video, we absorb around 1.5-2 μg B12 per meal through specific
absorption, and around 1-2% of the rest passively.
Most people get their B12 from food multiple times per day, so we'll look at that scenario
first.
If for example you got one third of that 2.4 μg with every meal, all of that amount would
be absorbed since .8 μg is below the 1.5-2 μg limit that can be absorbed through our
specific B12 mechanism, and we would absorb a full daily 2.4 μg with this small amount.
But as it pertains to supplementation, nobody takes a B12 supplement 3 times a day - they
are taken once a day or even less frequently.
If you took a single dose of 2.4 μg, again only 1.5-2 of this would be absorbed, leaving
us with a small but definite deficit that may add up to insufficiency in some people
over time.
This is where high-dose supplements come in.
If you instead took a 100 μg supplement, 1.5-2 μg would be absorbed specifically, along with
a further 1-1.5 μg through passive diffusion, adding up to at least 2.5 μg - providing us
with the RDA.
Some people opt to take their B12 weekly.
This is where the doses of B12 in the thousands of micrograms come in.
A common approach is to take a single dose of around 2000 μg of B12 once a week.
In this case, we absorb 1.5-2 μg specifically and a further 20-30 μg passively.
This will give us a minimum of 21.5 μg actually absorbed, which averages just over 3 per day,
again providing the RDA.
The next point is important - we're going to look at how much B12 we actually ingest
per week with each strategy.
In multiple daily dosing we take in 16.8 μg per week.
A daily dose of 100 μg adds up to 700 per week.
And that single weekly dose of 2000 μg of course provides 2000 per week, so clearly
it can really start to add up the less frequently we take the vitamin.
If you want to reduce that potential cancer risk we see associated with high-dose B12,
weekly dosing is not the best strategy.
Multiple daily dosing would allow us to expose ourselves to the least amount of B12, but
this dosing strategy is impractical and there are no supplements available with such small
doses of B12 on its own.
I believe a daily supplement of at least around 100 μg to be the best of both worlds - a practical
approach to supplementation that will not expose us to very high amounts of B12.
Unfortunately, these more moderately-dosed B12 supplements can be hard to find because
of the widespread practice of megadosing.
If you cannot find a supplement with a dose in the order of hundreds of micrograms, it
is better to opt for the weekly 2000 μg approach rather than something like a daily 1000 μg
supplement.
Of course, getting B12 from food multiple times per day would allow us to take in the
lowest amount of B12, but B12 does not occur naturally in foods on a plant-based diet.
You could focus on eating fortified foods multiple times per day, and if this is practicable
in your individual case it is probably the best option since you will be exposed to the
least amount of B12.
However, this strategy is less convenient and I believe less fool-proof, and you are
more likely to end up with sub-optimal intake and status relying on fortified foods alone.
Overall I think a daily supplement of at least around 100 μg cyanocobalamin to be the best
choice.
Indeed, unlike methylcobalamin, cyanocobalamin is permitted for use to fortify these foods
as well as for supplements, and is the form I recommend for supplementation and the form
that all the numbers discussed in this video apply to.
I will be discussing the four main forms of cobalamin in my next video along with how
I came to my recommendation for this form, so stay tuned for that one!
In summary, megadosing B12 may not be as safe as we once
thought, and there is now value in determining a more conservative dosing strategy that will
still provide optimal status in the individual.
In those with unimpaired absorption, decreasing frequency of B12 dosing requires a diproportionate
increase in total intake to provide the same amount of B12 actually absorbed.
To minimise total intake, multiple daily dosing would be optimal but is impractical.
A daily dose of at least around 100 μg per day may be a good middle ground to minimise exposure
whilst still having a high probability of ensuring adequacy.
If a more conservatively-dosed supplement is not available, doses of B12 in the order
of thousands of micrograms are better to be taken weekly than daily.
Regardless of supplementation strategy, it is important to check your status every so
often along with your regular bloodwork.
Thanks for watching, and I hope this video helped you make some sense of the issues around
B12 dosing.
Be sure to share this video with anyone you know that might be uninformed on this topic.
If there was something that wasn't clear from the video, feel free to let me know in the
comments and I'll get back to you.
Give us a thumbs-up if you found the video informative, and make sure you subscribe if
you haven't already so you don't miss the next one which will be on the different forms
of B12.
That's it for now though guys, talk to ye soon.
Sláinte!