Study recommends higher intakes of Vit D

[Guest guest]

Hi all:

Vitamin D dosage study determines proper dosage to achieve optimum

blood levels of 80 nanomoles per litre (nmol/L).

They determined:

Supplementation with 2000 IU is sufficient to raise levels to greater

than 50 nmol/L in most, but higher doses were needed to achieve

concentrations greater than 75 nmol/L in some.

2800 IU is needed if you have blood levels of 45 nmol/L, and 4000 IU

is needed if levels start at less than 45 nmol/L.

Dave

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Link:

http://www.nutraingredients.com/news/ng.asp?n=81998 & m=1NIED12 & c=lqeudkujayvvlpc

full text:

Vitamin D dose study adds weight to intake increases

By ls

12/12/2007- Doses of vitamin D3 of 2,000 International Units (IU) -

the current tolerable upper intake level (UL) in Europe and the US -

are needed to ensure blood levels of the vitamin amongst

post-menopausal African-American women, says a new study.

Over 200 women took part in the three year study, published in the

American Journal of Clinical Nutrition, which adds to an ever-growing

body of science suggesting an urgent need to review current daily

intakes of the vitamin.

Vitamin D is produced in the skin on exposure to UVB radiation and can

also be consumed in small amounts from the diet. However, increased

skin pigmentation reduces the effect of UVB radiation meaning darker

skinned people are more at risk of vitamin D deficiency.

Vitamin D deficiency can lead to a range of health problems, including

rickets, poor tooth formation, convulsions, general ill health, and

stunted growth. It has also been linked to an increased risk of

certain cancers, cardiovascular disease, diabetes, and osteoporosis.

Researchers from Winthrop University Hospital, Mineola, New York

performed a dose-response experiment with 208 healthy African-American

postmenopausal women. Half the women were assigned to the vitamin D

intervention arm of the trial and received daily supplements of 800 IU

D3 (20 micrograms) for two years, and 2,000 IU (50 micrograms) for the

final year.

Generally, blood levels of 25- hydroxyvitamin D (25(OH)D), the

non-active 'storage' form, of 50 nanomoles per litre (nmol/L) are

suggested as the lower limit of the normal range. Studies have

reported however that levels of parathyroid hormone (PTH), a hormone

that regulates calcium balance, and calcium absorption are not

optimised below serum 25(OH)D levels of 80 nanomoles per litre.

The authors, led by Talwar, report that the lower dose raised

25(OH)D levels from a baseline average of 47 nmol/L to 71.4 nmol/L

after three months. After three months at the higher dose (2,000 IU),

the average serum concentration of 25(OH)D was 87 nmol/L.

Moreover, 95 per cent of the participants achieved a serum 25(OH)D

concentration greater than 50 nmol/L, while levels greater than 75

nmol/L were achieved by only 60 per cent.

" Supplementation with 50 micrograms per day (2000 IU/d) oral vitamin

D3 is sufficient to raise serum 25-hydroxyvitamin D concentrations to

greater than 50 nmol/L in almost all postmenopausal African American

women, " wrote Talwar.

" However, higher doses were needed to achieve concentrations greater

than 75 nmol/L in many women in this population. "

Taking their results one step further, they formulated an algorithm in

order to allow for the prescription of vitamin D needed to achieve

optimal serum concentrations.

Talwar and co-workers report that a daily dose of 2800 IU is needed if

the individual has a starting 25(OH)D level of at least 45 nmol/L,

while a daily dose of 4000 IU is needed for individuals with 25(OH)D

levels less than 45 nmol/L.

Vitamin D refers to two biologically inactive precursors - D3, also

known as cholecalciferol, and D2, also known as ergocalciferol. The

former, produced in the skin on exposure to UVB radiation (290 to 320

nm), is said to be more bioactive. The latter is derived from plants

and only enters the body via the diet.

Both D3 and D2 precursors are hydroxylated in the liver and kidneys to

form 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form,

and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form

that is tightly controlled by the body.

A recent review of the science reported that the tolerable upper

intake level for oral vitamin D3 should be increased five-fold, from

the current tolerable upper intake level (UL) in Europe and the US of

2000 International Units (IU), equivalent to 50 micrograms per day, to

10,000 IU (250 micrograms per day) (American Journal of Clinical

Nutrition, March 2007, Vol. 85, pp 649-650).

Source: American Journal of Clinical Nutrition

December 2007, Volume 86, Number 6, Pages 1657-1662

" Dose response to vitamin D supplementation among postmenopausal

African American women "

Authors: S.A. Talwar, J.F. Aloia, S. Pollack and J.K. Yeh