The Joslin Diabetes Center apparently
has some doubts about metformin causing vitamin B12 deficiency.
Studies have shown that long-term metformin use causes about 30
percent of patients to develop B12 deficiency. Yet, Joslin believes
that food is the answer and waits until the last two paragraphs to
discuss to problems that vitamin B12 deficiency can cause. They even
try to minimize the deficiency and go to great lengths and quote the
American Diabetes Association to emphasize their point.
The unidentified blog author says, “But
just because these people taking metformin had lower levels of B12 in
their bloodstream doesn’t necessarily mean the B12 that’s there
isn’t getting the job done. New measurements of B12 activity have
indicated that although metformin does seem to reduce blood levels of
B12, this may not reduce the vitamin’s effectiveness in carrying
out it its functions in the body. When B12 doesn’t work the way
it’s supposed to, levels of something called total plasma
homocysteine (tHcy) go up. But newer studies looking at the levels of
tHcy in people who take metformin have found that they have not been
elevated.”
“According
to an article published this year in Diabetes Care, “low serum B12
alone without disturbances in the metabolic markers has no diagnostic
value.” From a practical standpoint, this means that if a B12
deficiency is suspected from a serum B12 test, further testing should
be undertaken before assuming the patient is B12 deficient.”
Vitamin B12 is one of the B vitamins
that are needed for the healthy development of blood cells, DNA, and
the nervous system. B12 is a water soluble vitamin and can possibly
be stored in the liver as long as one year. Vitamin B12 is obtained
from most animal products, fish, and especially animal liver. People
eating a vegan diet will need to consume a B12 supplement, B12
enriched tofu, or yeast to obtain adequate levels of vitamin B12.
This is important for people with type
2 diabetes and on metformin. B12 deficiency can lead to
megaloblastic anemia, a type of anemia in which the red blood cells
are significantly larger than normal. People with mild B12
deficiency may feel weak and tired, bleed easily, experience tingling
in the hands and feet (neuropathy), and swelling of the tongue.
People that experience severe B12 deficiency can have serious effects
such as memory loss, delusions, lost of taste and smell.
In the last paragraph, the author
finally admits that metformin contributes to serum B12 deficiency by
preventing its transfer into the blood through a calcium dependent
membrane. This leads to decreased absorption. For vitamin B12 to be
absorbed into the blood stream, it needs an acid environment in the
stomach.
As people get older and have the need
to take acid reducing medications, such as antacids or proton pump
inhibitors, they have the increase in the likelihood that they will
suffer from a B12 deficiency. It is also possible for this to happen
in certain gastrointestinal disorders such as atrophic gastritis,
Crohns disease, and surgical reduction of the stomach.
I admit I do not understand doctors
that fail to test for B12 deficiency properly and just tell people to
eat more meats. Few consider the person's age or ask what
medications the person is taking that might be a cause for B12
deficiency.
This article also helps justify B12
testing. Early Alzheimer's can be confused for B12 deficiency.
Please read the post linked.
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