>From the Finish paper posted by Jean-Louis:

>The vegans consuming Nori and/or Chlorella seaweeds (n = 16) had serum
vitamin
>B-12 concentrations twice as high as those not using these seaweeds (n = 5)
>(mean 221 pmol/L, range 75-408, vs. 105, 35-252, P = 0.025). In the
>longitudinal study, six of nine vegans showed slow, but consistent
>deterioration of vitamin B-12 status over a 2-y observation period. On the
>basis of these results we conclude that some seaweeds consumed in large
>amounts can supply adequate amounts of bioavailable vitamin B-12.

The following article from Vegetarian Times September 1991 contradicts the
above findings by pointing to more problems with B12 analogues:

                      "Looking for B12 in all the wrong places?"

"The list of vitamin B12 sources is getting smaller and smaller for vegans,
who avoid all animal foods.  Fermented foods such as soy-based tempeh and
miso were thought to be good sources until studies found that modern
sanitary manufacturing methods destroy the bacteria that would otherwise
produce B12.  Two recent studies published in the American Journal of
Clinical Nutrition indicate that some algae and sea vegetables - foods that
macrobiotics and vegans have long considered good sources of B12 - may also
fail to provide the nutrient.  The studies lend more weight to advice that
vegans need to supplement their diets with B12."

"The issue is complicated by the existence of B12 analogues - inactive
forms of the vitamin that do not satisfy human nutritional needs.  When
analyzed in the laboratory, certain algae and sea vegetables appear to be
rich in B12, and the blood of people who eat them also appears to contain
plenty of the vitamin."

"Unfortunately, laboratory analyses cannot distinguish B12 analogues from
the real thing. In order to determine whether a person is suffering from
B12 deficiency, researchers must assess the condition of the person's
corpuscular volume (MCV), which indicates the volume of the average blood
cell in a blood sample.  A high MCV indicates a B12 deficiency."

"In one of the two Journal studies, a group of researchers from the
Netherlands found that when children with B12 deficiency were fed the sea
vegetable nori or edible algae, their plasma B12 concentrations improved
but their MCV continued to increase.  Previous studies had indicated that
when children with a B12 deficiency were given a daily B12 supplement of as
little as 0.1 microgram, their bone marrow returned to normal after one
month.  In contrast, some of the children in this study were receiving up
to 27 times that amount daily from sea vegetables for four to six months,
yet they showed no improvement."

"Even if the children in the study were getting a legitimate source of B12,
it may have been sabotaged if taken with B12 analogues.  For instance, the
MCV decreased for all but one of the children who were fed fish, the one
whose level remained high was also eating nori.  The researchers speculated
that this child might have failed to improve because B12 analogues found in
the nori may have inhibited the metabolism of vitamin B12, but the
connection has yet to be proven."

"The second Journal study assessed the diet and B12 status of members of a
macrobiotic community, some of whom occasionally ate fish but most of whom
were vegans. Researchers found that people who ate tempeh, miso and sea
vegetables (including wakame and kombu, which have been considered highest
in B12) showed evidence of B12 deficiency, and concluded that sea
vegetables should not be recommended as a source of B12.  Bonny Specker,
medical researcher at the University of Cincinnati Medical Center in Ohio
and second author of the macrobiotic study, advises vegans to eat a cereal
that is fortified with B12 or take an occasional supplement."

Best, Peter
[log in to unmask]

PS.  To answer a private inquiry the information that I posted earlier this
week on spirulina and B12 was except for the last two paragraphs gathered
by Mark Thorsen a long-time anti-algae crusader on the net.