B-12 METHYLCOBALAMIN 1000 mcg 1 or 2 a day
Methylcobalamin is the preferred type. Cyanocobalamin must be converted to methyl or adenosyl cobalamin by the body. Required for fat and carbohydrate metabolism and formation of blood cells. Deficiency results in mental confusion, anemia, homocystenia, brain damage, tinnitus, asthma, and depression. B-12 deficiency leads to heart risk. (Science News 2-16-02) May benefit multiple sclerosis patients. Deficiency is widespread in people over sixty years of age. Blood test to determine B-12 level is recommended. Alcohol, estrogen, oral contraceptives, sleeping pills interfere with utilization. Natural sources are liver, beef, pork, eggs, milk, and cheese, except where soil is deficient in cobalt. (19) Needs calcium for absorption. Microwave cooking destroys B-12.
In a study of 64 patients taking 500 mcg of oral B-12 daily the lowest absorption rate was 1.8 mcg. Since this is less than the 2 mcg daily requirement a 500 mcg dosage would be insufficient. In most cases the mean absorption rate is 1.2 percent of intake. B-12 is widely available in 1000 and 2000 microgram potencies. No known toxicity. (27) For more information see "Oral Cobalamin for Pernicious Anemia, Medicine's Best Kept Secret", an editorial in the January 2, 1991 edition of the Journal of The American Medical Association.
(source:
http://foodsupplements.homestead.com/B12.html)