Vitamin B12 - Cobalamin
Cobalamin, or vitamin B12, one of the most recently isolated vitamins, is necessary in minute
amounts for the formation of nucleoproteins, proteins, and red blood cells, and for the functioning of the nervous system. Cobalamin deficiency
is often due to the inability of the stomach to produce glycoprotein, which aids in the absorption of this vitamin. Pernicious anemia results,
with its characteristic symptoms of ineffective production of red blood cells, faulty myelin (nerve sheath) synthesis, and loss of epithelium
(membrane lining) of the intestinal tract. Cobalamin is obtained only from animal sources—liver, kidneys, meat, fish, eggs, and
milk. Vegetarians are advised to take vitamin B12 supplements.
See: Other B Vitamins
More on Vitamin B12
What foods provide vitamin B12?
Vitamin B12 is naturally found in animal foods including fish, meat, poultry, eggs, milk, and milk
products. Fortified breakfast cereals are a particularly valuable source of vitamin B12 for vegetarians. Table 1 lists a variety of
food sources of vitamin B12.
Table 1: Selected food sources of vitamin B12
| Food |
Micrograms (μg)
per serving |
Percent
DV* |
| Mollusks, clam, mixed species, cooked, 3 ounces |
84.1 |
1400 |
| Liver, beef, braised, 1 slice |
47.9 |
780 |
| Fortified breakfast cereals, (100%) fortified), ¾ cup |
6.0 |
100 |
| Trout, rainbow, wild, cooked, 3 ounces |
5.4 |
90 |
| Salmon, sockeye, cooked, 3 ounces |
4.9 |
80 |
| Trout, rainbow, farmed, cooked, 3 ounces |
4.2 |
50 |
| Beef, top sirloin, lean, choice, broiled, 3 ounces |
2.4 |
40 |
| Fast Food, Cheeseburger, regular, double patty & bun, 1 sandwich |
1.9 |
30 |
| Fast Food, Taco, 1 large |
1.6 |
25 |
| Fortified breakfast cereals (25% fortified), ¾ cup |
1.5 |
25 |
| Yogurt, plain, skim, with 13 grams protein per cup, 1 cup |
1.4 |
25 |
| Haddock, cooked, 3 ounces |
1.2 |
20 |
| Clams, breaded & fried, ¾ cup |
1.1 |
20 |
| Tuna, white, canned in water, drained solids, 3 ounces |
1.0 |
15 |
| Milk, 1 cup |
0.9 |
15 |
| Pork, cured, ham, lean only, canned, roasted, 3 ounces |
0.6 |
10 |
| Egg, whole, hard boiled, 1 |
0.6 |
10 |
| American pasteurized cheese food, 1 ounces |
0.3 |
6 |
| Chicken, breast, meat only, roasted, ½ breast |
0.3 |
6 |
*DV = Daily Value. DVs are reference numbers developed by the Food and Drug Administration (FDA) to help consumers determine if a
food contains a lot or a little of a specific nutrient. The DV for vitamin B12 is 6.0 micrograms (μg). Most food labels do not list a
food's vitamin B12 content. The percent DV (%DV) listed on the table indicates the percentage of the DV provided in one serving. A
food providing 5% of the DV or less is a low source while a food that provides 10-19% of the DV is a good source. A food that provides 20% or
more of the DV is high in that nutrient. It is important to remember that foods that provide lower percentages of the DV also contribute to a
healthful diet. For foods not listed in this table, please refer to the U.S. Department of Agriculture's Nutrient Database Web site:
http://www.nal.usda.gov/fnic/cgi-bin/nut_search.pl.
Recommendations for vitamin B12 are provided in the Dietary Reference Intakes (DRIs) developed by the Institute of
Medicine of the National Academy of Sciences. Dietary Reference Intakes is the general term for a set of reference values used for
planning and assessing nutrient intake for healthy people. Three important types of reference values included in the DRIs are Recommended
Dietary Allowances (RDA), Adequate Intakes (AI), and Tolerable Upper Intake Levels (UL). The RDA recommends the average
daily intake that is sufficient to meet the nutrient requirements of nearly all (97-98%) healthy individuals in each age and gender group. An AI
is set when there is insufficient scientific data available to establish a RDA. AIs meet or exceed the amount needed to maintain a nutritional
state of adequacy in nearly all members of a specific age and gender group. The UL, on the other hand, is the maximum daily intake
unlikely to result in adverse health effects. Table 2 lists the RDAs for vitamin B12, in micrograms (μg), for children and adults.
Table 2: Recommended Dietary Allowances (RDA) for vitamin B12 for children and adults
Age
(years) |
Males and Females
(μg/day) |
Pregnancy
(μg/day) |
Lactation
(μg/day) |
| 1-3 |
0.9 |
N/A |
N/A |
| 4-8 |
1.2 |
N/A |
N/A |
| 9-13 |
1.8 |
N/A |
N/A |
| 14-18 |
2.4 |
2.6 |
2.8 |
| 19 and older |
2.4 |
2.6 |
2.8 |
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"Vitamin," Microsoft® Encarta® Online Encyclopedia 2005
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