. "N Estimation of the Period Covered by Vitamin B12 Stores." Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: The National Academies Press, 1998.
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DRI Dietary Reference Intakes: For Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline
TABLE N-1 Table of Ratiosa Used to Estimate the Extent of Protection from Vitamin B12 Stores
Initial Store, mg
Vitamin B12 Threshold, µg
1
2
3
4
5
6
7
8
9
10
350
3
6
9
11
14
17
20
23
26
29
300
3
7
10
13
17
20
23
27
30
33
250
4
8
12
16
20
24
28
32
36
40
200
5
10
15
20
25
30
35
40
45
50
150
7
13
20
27
33
40
47
53
60
67
100
10
20
30
40
50
60
70
80
90
100
a This represents the initial vitamin B 13 stores divided by the level of stores at which signs of vitamin B12 deficiency may become evident.
Table N-1 provides the ratio of the expected stores of an individual (in milligrams) to the threshold level of stores at which signs of vitamin B12 deficiency may appear. Usually the threshold value is not known, but studies suggest that it may be approximately 300 µg of vitamin B12 for adults (Bozian et al., 1963).
Tables N-2 and N-3 give the expected length in days (Table N-2) or years (Table N-3) for a given turnover rate and ratio from Table N-1 that body stores of vitamin B12 will sustain health in the individual. For example, from Table N-1 the ratio for an initial store of 3 mg of vitamin B12 and a threshold of 300 µg of vitamin B12 is 10. If the turnover rate is 0.1, the store would be expected to last 2,303 days, or 6.3 years.
REFERENCE
Bozian RC, Ferguson JL, Heyssel RM, Meneely GR, Darby WJ. 1963. Evidence concerning the human requirement for vitamin B12. Use of the whole body counter for determination of absorption of vitamin B12. Am J Clin Nutr 12:117– 129.
