Vitamin B-12 Requirements
eee at netcom.com
Sat Feb 8 12:19:32 EST 1997
Does _Drosophila_ have the same sort of requirements for
"true" B-12 that mammals have, or can they get along
on the B-12 analogs that have no nutritional B-12
activity in humans? The reason I ask is that I've seen
people talking about using yeast and fungus as nutritional
supplements for culture medium, and I know these are not
effective sources of B-12 for humans.
I've appended a file that I originally prepared for
use in an on-going flamewar in the quack... er, "alternative"
medicine newsgroups regarding blue-green algae being sold
as a cure for whatever ails you.
VICTOR HERBERT MD ON BLUE-GREEN ALGAE
Copyright 1996 Mark Thorson
[An analog (or "analogue") is a molecule that is a
modified form of another molecule. For example,
heroin and codeine are analogs of morphine. There
are analogs of vitamin B-12 which do not contribute
toward nutritional vitamin B-12 activity, and they
may even block absorption of "true" B-12 by occupying
the receptor sites for the IF/B-12 complex.]
Quoting in whole an April 26, 1995 letter to Sharon
Gordon, Consumer Complaint Coordinator, FDA (Philadelphia
District) from Victor Herbert MD, a leading scientist
on vitamins and nutritional diseases (and also author
of additional quotes which follow on non-nutritional
analogs of vitamin B-12):
"Dear Ms. Gordon:"
"I received a copy of the April 18 letter to you from
attorney ---------------- on the above subject. This is
to advise both you and him that many algae products are
falsely represented as containing vitamin B-12. As we
published a decade ago in _The_New_England_Journal_of_
_Medicine_, they contain only analogs of B-12, and no
"Analogs of B-12 are worthless, and possibly harmful,
to humans. One of the harms they may produce, in patients
with negative B-12 balance (which is very possible in
------------, a Type I diabetic, age --), is to accelerate
the development of B12-deficiency neuropathy in feet,
legs, and hands. ------------ should see a neurologist
to determine if he has B12-deficient neuropathy."
------------ should have his B-12 status determined by
measurement of his serum levels of vitamin B-12, homo-
cysteine, and holotranscobalamin (holo TC II). Holo TC II
will be low before any other tests for negative B-12
status become low (see our 1994 paper in _American_
_Journal_of_Clincal_Nutrition_ on assessing B-12 status).
If the Cell Tech product:
a. contains analogs of B-12, and,
b. its label does not contain a consumer warning stating,
'WARNING: contains vitamin B-12 analogs but no vitamin
B-12. Do not take this product unless your vitamin B-12
status has been evaluated by a responsible health
professional and found to be normal', then it is my
perception that the seller has violated product liability
law, i.e., he has a duty to warn, and he failed to warn."
"Victor Herbert, M.D., J.D."
Quoting from "Staging vitamin B-12 (cobalamin) status in
volume 59 (supplement), pages 1213S-1222S:
"About one-third of the 'vitamin B-12' in serum is in fact
not cobalamins (which are all forms of vitamin B-12 that
are active for humans), but other corrinoids that are
metabolically dead for humans but active for bacteria.
Thus, many microbiologic assays may find normal 'vitamin
B-12' concentrations in vitamin B-12-deficient people
because the assay is reading as vitamin B-12 what is
in fact noncobalamin corrinoids."
Quoting from "Vitamin B-12: plant sources, requirements,
and assay", _American_Journal_of_Clinical_Nutrition_,
volume 48, pages 852-858:
"Vitamin B-12 is of singular interest in any discussion
of vegetarian diets because this vitamin is not found
in plant foods as are other vitamins. Confusion about
what sources may yield vitamin B-12 to strict vegetarians
has arisen because the standard US Pharmacopeia (USP)
assay for vitamin B-12 does not assay only vitamin B-12.
In the USP method the content of vitamin B-12 of any given
food is determined by making a water extract of that food
and feeding the extract to a bacterium (_Lactobacillus_
_leichmannii_). The quantity of vitamin B-12 is
determined by the amount of bacterial growth. The problem
is that what is active vitamin B-12 for bacteria is not
necessarily active vitamin B-12 for humans. Many of the
papers in the literature give values of vitamin B-12 in
food that are false because as much as 80% of the activity
by this method is due to inactive analogues of vitamin
"We studied several types of tempeh, including Original
Soy Tempeh, a _Rhizobus_oligosporus_ culture with a label
claim of 160% of the US RDA for vitamin B-12 per 4 oz.
Using the differential radioassay we found there was
practically no vitamin B-12 in it."
"We also studied most of the spirulinas sold in health
food stores as sources of vitamin B-12; there is
practically no vitamin B-12 in them. The so-called
vitamin B-12 is almost exclusively analogues of vitamin
B-12 and we have extracted the two largest peaks of
analogues and they actually block vitamin B-12 metabolism.
We suspect that people taking spirulina as a source
of vitamin B-12 may get vitamin B-12 deficiency quicker
because the analogues in the product block human
mammilian cell metabolism in culture and we suspect
they will also do this in the living human. Remember
that the label claim of vitamin B-12 is actually a
claim of corrinoid content, not vitamin B-12 content."
Quoting from "_Spirulina_ and Vitamin B-12", _Journal_of_
_the_American_Medical_Association_, volume 248, number 23,
"A current health food fad involves tablets of
_Spirulina_, a genus of blue-green algae belonging
to the family _Oscillatoriaceae_ of the division
_Cyanophyta_, represented in the health food literature
to contain large amounts of vitamin B-12."
"We subjected three popular brands of 500-mg _Spirulina_
tablets to both the _United_States_Pharmacopeia_
microbiologic assay for vitamin B-12 and the vitamin
B-12 radioassay method we recently applied to multivitamin
"Microbiologic assay would lead one to believe that 500-mg
_Spirulina_ tablets contain about 0.25 to 1 microgram of
vitamin B-12 per tablet, but radioassays, using R binder
to measure the total of (cobalamins plus cobalamin
analogues) and intrinsic factor to measure cobalamins
alone (ie, 'true B-12'), suggest that more than 80%
of what appears to be 'vitamin B-12' by microbiologic
assay is in fact analogues of B-12."
"Elsewhere, we reported that 10% to 30% of the vitamin
B-12 activity in multivitamin/mineral pills may be
analogues created by the antioxidant actions of iron,
vitamin C, and other ingredients in the pills. In all
of these preparations, there was more true B-12 than
analogues; in _Spirulina_, the reverse was the case.
These findings are consistent with studies three decades
ago, indicating that sewage and other organisms make a
variety of vitamin B-12 analogues that have no vitamin
B-12 activity for humans, ..."
More information about the Dros