The Food and Nutrition Board has recommended that elderly people obtain 2.4 micrograms of vitamin B12 daily—from verifiable sources, e.g., either from eating fortified foods, such as cereals, that clearly identify the amount of vitamin B12 per serving and/or from vitamin B12 supplements.
Claims that vitamin B12 can enhance exercise performance and that it is an "energizer" have not been tested and are based upon anecdotal accounts.
Again, vitamin B12 supplementation is highly advised for vegetarians, especially children who are vegetarians. Vegetarians whose diets allow for the regular use of eggs and dairy products can generally obtain enough vitamin B12 from their diets
A typical dose of B12 (cyanocobalamin) in nutritional supplements used by pregnant women and nursing mothers is 12 micrograms daily. Pregnant women and nursing mothers should only use doses higher than this if recommended by their physicians.
Administration of doses of vitamin B12 greater than 10 micrograms daily may produce a hematological response in those with anemia secondary to folate deficiency.
DOSAGE AND ADMINISTRATION
The principal form of B12 used in nutritional supplements is cyanocobalamin. Methylcobalamin is also available for nutritional supplementation. Hydroxocobalamin is presently only available for parenteral use.
Cyanocobalamin is available as a single ingredient product and in multivitamin, multivitamin/multimineral and B complex products. Lozenges of cyanocobalamin and methylcobalamin are also available. Prenatal and postnatal vitamin/mineral formulas typically deliver a dose of 12 micrograms of B12 daily. A general range of B12 dosage is 3 to 30 micrograms daily. Some use much higher doses. Absorption of naturally occurring B12 decreases with age. Because of this, the Food and Nutrition Board advises that those older than 50 years should consume foods fortified with B12 or take a vitamin B12-containing nutritional supplement in order to meet the RDA (2.4 micrograms daily).
Those with B12 deficiency may be managed with high doses of oral B12. However, this requires prescription and management by a physician.
The Food and Nutrition Board of the Institute of Medicine of the National Academy of Sciences has recommended the following Dietary Reference Intakes (RDI) for vitamin B12:
InfantsAdequate Intakes (AI)0 through 6 months0.4 micrograms/day ~ 0.05 micrograms/Kg7 through 12 months0.5 micrograms/day ~ 0.05 micrograms/Kg ChildrenRecommended Dietary Allowance (RDA)1 through 3 years0.9 micrograms/day4 through 8 years1.2 micrograms/day Boys9 through 13 years1.8 micrograms/day14 through 18 years2.4 micrograms/day Girls9 through 13 years1.8 micrograms/day14 through 18 years2.4 micrograms/day Men19 years and older2.4 micrograms/day Women19 years and older2.4 micrograms/day Pregnancy14 through 50 years2.6 micrograms/day Lactation14 through 50 years2.8 micrograms/day The U.S. RDA, for vitamin B12, the value used for nutritional supplement and food labeling purposes, is 6 micrograms daily.
Vitamin B12 is available by prescription in the following forms and strengths:
— 100 mcg/mL, 1000 mcg/mL
— 500 mcg/0.1 mL
Vitamin B12 is available in the following forms and routes for OTC use:
— 100 mcg, 250 mcg, 500 mcg
— 500 mcg, 1000 mcg, 2000 mcg, 2500
mcg, 5000 mcg
— 50 mcg, 100 mcg, 250 mcg, 500 mcg, 1000 mcg
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