All of vitamin B12 in nature is of microbial origin. Cobalamin, as vitamin B12
should correctly be termed, is a large polar molecule that
must be bound to specialized transport proteins to gain entry into cells. Entry
from the lumen of the intestine under physiological
conditions occurs only in the ileum and only when bound to intrinsic factor. ...
In most bacteria and in all mammals, cobalamin
regulates DNA synthesis indirectly through its effect on a step in folate
metabolism, the conversion of N5-methyltetrahydrofolate to
tetrahydrofolate, which in turn is linked to the conversion of homocysteine to
methionine. (1)
Vitamin K, intrinsic factor can be synthesized in the gut by lactobacillus
acidophilus. However lactobacillus acidophilus does not
always flourish in the gut of the autist. Attempts to supplement this bacteria
often fail and repeat testing confirms no measurable levels
of the lactobacillus acidophilus even with heavy prescribed supplementation
especially for those on diets which are devoid of lactose.
Attempting to treat a single area without looking at the whole picture which
includes diet can also result in testing and supplementation
with P-5-P and this supplement can inhibit the PST-P enzyme which has already
been found at abnormally low levels in the autist
population (Waring, Ngong).
This reaction occurs in the cytoplasm, and it is catalyzed by methionine
synthase, which requires methyl cobalamin (MeCbl), one of
the two coenzyme forms of the vitamin, as a cofactor. Defects in the generation
of MeCbl (cobalamin E and G diseases) result in
homocystinuria; affected infants present with megaloblastic anemia, retardation,
and neurological and ocular defects. 5'-Deoxyadenosyl
cobalamin (AdoCbl), the other coenzyme form of cobalamin, is present within
mitochondria, and it is an essential cofactor for the
enzyme Methylmalonyl-CoA mutase, which converts L-methylmalonyl CoA to succinyl
CoA. This reaction is in the pathway for the
metabolism of odd chain fatty acids via propionic acid, as well as that of the
amino acids isoleucine, methionine, threonine, and valine.
Impaired synthesis of AdoCbl (cobalamin A or B disease) results in infants with
methylmalonic aciduria who are mentally retarded,
hypotonic, and who present with metabolic acidosis, hypoglycemia, ketonemia,
hyperglycinemia, and hyperammonemia. Megaloblastic
anemia does not develop in these children because adequate amounts of MeCbl are
present, but the effect of methylmalonic acid on
marrow stem cells may give rise to pancytopenia. Congenital absence of
reductases in the cytoplasm, which normally reduce the
cobalt atom in cobalamin from its oxidized to its reduced state (cobalamin C and
D diseases), results in impaired synthesis of both
MeCbl and AdoCbl. Both methylmalonic aciduria and homocystinuria therefore
develop in these children, and they present with
megaloblastosis, mental retardation, a host of neurological and ocular
disorders, and failure to thrive; however, they do not have
hyperglycinemia or hyperammonemia. A similar biochemical profile and clinical
presentation is also seen in cobalamin F disease,
which results from a defect in the release of cobalamin from lysosomes,
following receptor-mediated endocytosis of the transcobalamin
II-cobalamin complex into cells. It is important to recognize these inborn
errors of cobalamin absorption, transport, or function as soon
after birth as possible, because most respond (in some patients more fully than
others) to parenteral administration of cobalamin.
Delays in diagnosis can lead to grave clinical consequences. (1)
Some autists respond well to B12 injections, it is important to know which form
of B12 to use. I have within my case histories an
individual diagnosed with cobalamin F disease. She responded well to the lutein
free, nutrient balanced diet and her previous diagnosis
was reversed.
Cobalamin (vitamin B12) is an essential nutrient derived exclusively from
bacterial sources. Untreated deficiency, caused by either the
autoimmune disease pernicious anemia or nutritional lack, results in a
macrocytic anemia and/or subacute combined degeneration of
the spinal cord and is eventually fatal. Strict vegetarians have long been
known to be at risk of cobalamin deficiency, which develops
insidiously over many years. Any individual with reduced ability to split
cobalamin from food-protein may also become deficient even
though intrinsic factor is present. Diagnosis of cobalamin deficiency has
frequently relied on total serum cobalamin and the Schilling
test. Newer approaches such as analysis of methylmalonic acid, homocyst(e)ine,
holotranscobalamin, anti-intrinsic factor antibodies,
and serum gastrin may provide more cost-effective testing, as well as identify
those with a covert deficiency. (2)
Vitamin K, clotting factor, can be taken in the diet from oils such as soy and
olive. In a population which may not produce adequate or
any lactobacillus acidophilus growth it is important to provide the vitamin K, B
vitamins and control of yeast overgrowth from diet,
supplements and/or pharmaceuticals.
Intrinsic factor-vitamin B12 IF-B12 affinity chromatography of renal cortex
membrane from rabbit and man yielded the same
approximately 460-kDa protein. Binding studies including surface plasmon
resonance analyses of the protein demonstrated a calcium-
dependent and high affinity binding of IF-B12 to a site distinct from the RAP
binding site. The high affinity binding of IF-B12 was
dependent on complex formation with vitamin B12. (3)
Looking exclusively at one nutrient rarely will get the desired results. The
human body relies on many essential nutrients and these
need to be balanced in order for our bodies to function optimally.
Uptake of vitamin B12 (cyanocobalamin) is facilitated by the cobalamin-binder
gastric intrinsic factor (IF), which recognizes a 460-kD
receptor, cubilin, present in the epithelium of intestine and kidney. Using
fluorescence in situ hybridization, radiation hybrid mapping,
and screening of YAC clones, the human cubilin gene was mapped between the
markers D10S1661 and WI-5445 on the short arm of
chromosome 10. This is within the autosomal recessive megaloblastic anemia
(MGA1) 6-cM region harboring the unknown recessive-
gene locus of juvenile megaloblastic anemia caused by intestinal malabsorption
of cobalamin (Imerslund-Gräsbeck's disease). In
conclusion, the present molecular and genetic information on human cubilin now
provides circumstantial evidence that an impaired
synthesis, processing, or ligand binding of cubilin is the molecular background
of this hereditary form of megaloblastic anemia. (4)
Some populations are at higher risk for B12 deficiencies.
At one time, the diagnosis of a deficiency of vitamin B12 or folate was
considered to be relatively straightforward. As knowledge has
accumulated, the limitations of such tests as serum vitamin level measurements
and the Schilling test have become apparent. With the
development of newer tests, atypical and subclinical deficiency states have been
recognized. (5)
1. Vitamin B12 in health and disease: part I--inherited disorders of function,
absorption, and transport. Kapadia CR. Department of
Digestive Diseases, VA Medical Center, West Haven, CT 06516, USA.
Gastroenterologist, 1995 Dec, 3:4, 329-44
2. Cobalamin. Markle HV, Centenary Health Centre, Scarborough, Ontario, Canada.
Crit Rev Clin Lab Sci, 1996, 33:4, 247-356
3. Characterization of an epithelial approximately 460-kDa protein that
facilitates endocytosis of intrinsic factor-vitamin B12 and binds
receptor-associated protein. Birn H; Verroust PJ; Nexo E; Hager H; Jacobsen C;
Christensen EI; Moestrup SK, Department of Cell
Biology, 8000 Aarhus C, Denmark. J Biol Chem, 1997 Oct, 272:42, 26497-504
4. The human intrinsic factor-vitamin B12 receptor, cubilin: molecular
characterization and chromosomal mapping of the gene to 10p
within the autosomal recessive megaloblastic anemia (MGA1) region. Kozyraki R;
Kristiansen M; Silahtaroglu A; Hansen C; Jacobsen
C; Tommerup N; Verroust PJ; Moestrup SK Institut National de la SantÆe et de la
Recherche MÆedicale, U489, HÈopital Tenon,
Paris, France. Blood, 1998 May, 91:10, 3593-600
5. Laboratory diagnosis of vitamin B12 and folate deficiency: a guide for the
primary care physician. Snow CF Division of Primary Care,
Santa Clara Valley Medical Center, San Jose, Calif., USA. Arch Intern Med, 1999
Jun, 159:12, 1289-98
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Sara's Diet - a comprehensive dietary approach to autism
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