For those eating plant-based diets, encouragement of vitamin B12 supplementation cannot be overemphasized. Surprisingly, there are no consensus clinical guidelines on preventing, diagnosing, and treating B12 deficiency.
This is the first video in a five-part series on vitamin B12. Stay tuned for:
• The Best Way to Test for Vitamin B12 Deficiency (https://nutritionfacts.org/video/the-best-way-to-test-for-vitamin-b12-deficiency)
• The Best Source of Vitamin B12: Supplements, Shots, or Fortified Foods? (https://nutritionfacts.org/video/the-best-source-of-vitamin-b12-supplements-shots-or-fortified-foods)
• How Much Vitamin B12 Do We Need Each Day? (https://nutritionfacts.org/video/how-much-vitamin-b12-do-we-need-each-day)
• Are Large Weekly Doses of Vitamin B12 Safe? (https://nutritionfacts.org/video/are-large-weekly-doses-of-vitamin-b12-safe)
For more on vitamin B12, check out the topic page (https://nutritionfacts.org/topics/vitamin-b12/).
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-Michael Greger, MD FACLM
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These next five videos I’m going to
be covering everything Vitamin B12. How fast B12 deficiency can set in,
the earliest signs to watch out for, why standard blood tests can miss it, and just how dangerous
it can be left untreated. Most importantly,
the best way to protect yourself. “How Long Does It Take to Become Vitamin B12 Deficient
and What Are the Symptoms?” For those eating
plant-based diets, encouragement
of vitamin B12 supplementation cannot be overemphasized. What happens
if you don’t get enough B12? Well, the vitamin is necessary
for the synthesis of DNA, so, a deficiency in B12
can cause pretty much anything. Brain problems,
psychiatric problems, sensory problems,
constitutional problems, muscle problems,
nerve problems. It can also cause
clotting disorders and bleeding disorders. It can make people catatonic, hallucinate, psychotic,
even suicidal. One patient
got electroshock therapy before they realized, “Oops, he was just
B12 deficient.” Even more tragic are
life-threatening manifestations of B12 deficiency in infants when their moms
aren’t supplementing; coma, respiratory failure,
severe brain damage. Vitamin B12 deficiency
in pregnancy is a diagnosis not to miss. I’ve done B12 videos like this over and over again
over the years. Can we just stick
to the consensus clinical guidelines
on preventing, diagnosing,
and treating B12 deficiency? No, we can’t
because there aren’t any. There are lots
of recommendations out there but little robust evidence
to back them up. They’re based
more on assumptions than solid clinical evidence. That’s why you’ll see
papers like this, “How I Treat
Vitamin B12 Deficiency.” Why should we care what
some random doctor does? Because there aren’t
a lot of clear-cut answers everyone agrees upon. For example,
it is currently unknown how long it takes
for vitamin B12 deficiency to occur in someone
going completely plant-based without supplementing with B12
or B12-fortified foods. This textbook
suggested it might take as long as 10 or 20 years, but that was based
on a study of baboons and a single case report. On the flipside
are those suggesting we can see evidence
of a functional B12 deficiency within four weeks, but if you look at that source,
that’s not right either. Three years is a common
time frame we hear, but that’s just from this
70-year-old autopsy study where a back-of-the-envelope
calculation said that if the average liver weighs
like three pounds (1.35 kg), and B12 is stored in the liver, and there’s a certain amount
of B12 per gram, then the average liver
would contain enough for three years,
but that’s just all in theory. If we look at people undergoing a type
of bariatric surgery that messes with B12 absorption, we start seeing problems
within just a few months in terms of impaired metabolism, a rise in methylmalonic acid
and homocysteine, two compounds that are normally
cleared, in part, by B12. This challenges the concept
that liver stores of B12 were sufficient
for long-term maintenance of adequate B12 status. Here’s an interesting
recent case. A vegan who had been taking B12 decided to stop it
for undisclosed reasons. This allowed
for a natural experiment. Though his blood levels of B12
stayed within normal limits, his homocysteine
went through the roof. We like to see it
below 12 µmol/L, but it jumped to 18 µmol/L
in a matter of months, though there is
a complicating factor. His folate plunged
at the same time, and folate is also necessary
to detoxify homocysteine. Evidently, when he stopped
supplementing with B12, he also stopped eating
as many fruits and vegetables, folate
is concentrated in greens, because it was wintertime
and his access was limited, so that may have
contributed, too. The bottom line,
the researchers concluded, is that this
reiterates the need for continuous
B12 supplementation in persons following
an unfortified plant-based diet. Some medical professionals
even suggest it might be
a good preventative measure for all vegans to annually
check their B12 status. The number one question
primary care doctors are advised to ask
symptomatic patients on a plant-based diet is, “What Is Your Preferred
Source of Vitamin B12?”
