Dwight Hoo
Mon, Jul-01-02, 06:55
Subject Vitamin D:
First some background information. 1 U.S.P. = 1 I.U. = 0.025
micrograms. 66 to 165 I.U. per 100 milliliter of serum is the
normal range. Converting the low value of the range 66 to
micrograms per liter yields 16.5 micrograms per liter. The RDA
for women age 23 or older is 200 IU. This value previously was
held to be 400 IU by "authorities." The major storage and
transport form is either 25-hydroxy-ergocalciferol or
25-hydroxy-cholecalciferol from respectively D2 and D3.
Now the discussion. Kelley S. Scanlon et al report in AJCN
find that many women ages 15 to 49 are short on vitamin D. The
study was broken in two populations, African American and
European American. The threshold at which the individuals were
considered deficient was 15 mcg per liter of 25(OH)D. Of the
1546 blacks, 42% were below the threshold. Among the 1426
whites, 4.2% were below the threshold. Both groups were
non-pregnant. To my mind even a 4.2% deficiency is wildly high
given the easy treatment and 42% is utterly outrageous. The
exact 10X seems a little odd given that it is exact:-)
Now an interesting point. In a sub-population of the blacks,
those taking supplement containing 200 to 400 IU qd a full 30%
were still below the threshold!
Hence the comment by Michael F. Holick of Boston Univ. that
those person not getting enough sun (apparently a large
percent of the population) the current RDA should be raised by
four times or more.
Note also, the elderly (of all skin pigmentation levels) have
greatly reduced ability to form vitamin D at the skin. A
population not considered in this study.
It would seem that this value should be screened by GP's, that
way they can not only suggest a supplement by also suggest a
supplement dose. Especially as some individuals are vitamin D
sensitive while others are resistent. It seems that an intake
beginning at 1200 IU qd can increase the risk of heart attack
and kidney stones. How much of an increased risk, I don't
know. Holick is clearly suggesting at least 800 IU qd for many
or even a 1000 IU qd is desirable.
Now a question, can getting lots of sun increase ones chances
of kidney stones? I need to review the negative feedback
mechanisms. I recall one as 25(OH)D is converted to the active
form by 1a-hydroxylase found mostly but not solely in the
kidneys. The result is the major ligand for the D receptors. I
recall there feedback mechanism at the D3 to calcitrol level
but is there one earlier at 7-dehydrocholesterol to D3 level
of formation?
This not a vitamin to go mega on.
DH
First some background information. 1 U.S.P. = 1 I.U. = 0.025
micrograms. 66 to 165 I.U. per 100 milliliter of serum is the
normal range. Converting the low value of the range 66 to
micrograms per liter yields 16.5 micrograms per liter. The RDA
for women age 23 or older is 200 IU. This value previously was
held to be 400 IU by "authorities." The major storage and
transport form is either 25-hydroxy-ergocalciferol or
25-hydroxy-cholecalciferol from respectively D2 and D3.
Now the discussion. Kelley S. Scanlon et al report in AJCN
find that many women ages 15 to 49 are short on vitamin D. The
study was broken in two populations, African American and
European American. The threshold at which the individuals were
considered deficient was 15 mcg per liter of 25(OH)D. Of the
1546 blacks, 42% were below the threshold. Among the 1426
whites, 4.2% were below the threshold. Both groups were
non-pregnant. To my mind even a 4.2% deficiency is wildly high
given the easy treatment and 42% is utterly outrageous. The
exact 10X seems a little odd given that it is exact:-)
Now an interesting point. In a sub-population of the blacks,
those taking supplement containing 200 to 400 IU qd a full 30%
were still below the threshold!
Hence the comment by Michael F. Holick of Boston Univ. that
those person not getting enough sun (apparently a large
percent of the population) the current RDA should be raised by
four times or more.
Note also, the elderly (of all skin pigmentation levels) have
greatly reduced ability to form vitamin D at the skin. A
population not considered in this study.
It would seem that this value should be screened by GP's, that
way they can not only suggest a supplement by also suggest a
supplement dose. Especially as some individuals are vitamin D
sensitive while others are resistent. It seems that an intake
beginning at 1200 IU qd can increase the risk of heart attack
and kidney stones. How much of an increased risk, I don't
know. Holick is clearly suggesting at least 800 IU qd for many
or even a 1000 IU qd is desirable.
Now a question, can getting lots of sun increase ones chances
of kidney stones? I need to review the negative feedback
mechanisms. I recall one as 25(OH)D is converted to the active
form by 1a-hydroxylase found mostly but not solely in the
kidneys. The result is the major ligand for the D receptors. I
recall there feedback mechanism at the D3 to calcitrol level
but is there one earlier at 7-dehydrocholesterol to D3 level
of formation?
This not a vitamin to go mega on.
DH