There has been much discussion on vitamin D lately, and a lot of random dose suggestions. Here is a recent one that shows large dose response differences (estimations) between studies.
The following is a summary from the following study:
Cashman KD, et al. Estimation of the dietary requirement for vitamin D in healthy adults. American Journal of Clinical Nutrition. 2008.
-Vitamin D deficiency is defined as a serum or plasma 25-OHD concentration of <10-25 nmol/L.
-In the UK, 25 nmol/L is the low threshold.
-Research has suggested that the low limit be increased
-Less than 50 nmol/L may be associated with a greater risk for nonskeletal chronic diseases
- n=245 (Cork, Ireland and Coleraine [lat=51 degrees N], Northern Ireland (UK) [lat=55 degrees N])
- white men and women aged 20-30 and 30-40
- t=22 weeks (October 2006-March 2007)
- exclusion criteria: consumption of vitamin D supplements for 12 weeks before study or if a winter vacation was planned (cutaneous synthesis), mental illness, hypercalcemia, intestinal malabsorption syndrome, excessive alcohol consumption, medications that interfere with D metabolism, or pregnancy plans
- double-blind, placebo-controlled
- subjects randomly assigned 0, 5, 10, or 15 micrograms (0, 200, 400, 600 IU)
- sun exposure recorded
- attrition: 24
- Vit D3 (cholecalciferol)
- Male average dietary intake: D-152 IU Calcium-1128mg vs female: D-132 IU Calcium-803mg
Subjects who reported summer sun exposure had a higher baseline serum 25OHD concentration compared to those who reported avoiding or sometimes having exposure (82.4 nmol/L vs 65.2 nmol/L.)
- Total vitamin D intake (diet plus supplemental vitamin D) increased in a dose-related manner with supplementation (4.4 ? 3.6, 9.1 ? 2.4, 13.9 ? 2.0, and 19.2 ? 3.1 ?g/d in the placebo and 5, 10, and 15 ?g vitamin D/d groups, respectively
- Slope relating intake and serum 25OHD = 1.96 nmol/L per 40IU (though another study reported only .70 nmol/L per 40IU)
- "Using mathematical modeling of the vitamin D intake?status data, we estimated that the vitamin D intakes that maintained serum 25(OH)D concentrations >25 nmol/L in 90%, 95%, and 97.5% of the 20?40-y-old adults were 2.7, 5.9, and 8.7 ?g/d, respectively." (that is 108, 236, 348 IU/day)
- "Data on sun preference also were incorporated into the model; the vitamin D intakes that maintained serum 25(OH)D concentrations of 25 nmol/L in 97.5% of the sample were 7.2, 8.8, and 12.3 ?g/d in those who reported often having sunshine exposure, those who sometimes had sunshine exposure, and sunshine avoiders, respectively" (288, 352, 492 IU/day)
- "The vitamin D intakes that maintained serum 25(OH)D concentrations above 2 other commonly suggested cutoffs in 97.5% of the sample were 26.1, 27.7, and 31.0 ?g/d (for 50 nmol/L) (1044, 1108, 1240 IU) and 38.9, 40.6, and 43.9 ?g/d (for 80 nmol/L) in those who reported often having sunshine exposure, those who sometimes had sunshine exposure, and sunshine avoiders, respectively." (1556, 1624, 1756 IU/day)
- Another study (Heaney et al.) estimated that 4560IU/day was necessary to maintain above 80nmol/L in 97.5% of subjects, vs this study only (an estimated) 1640 IU/day was needed. Though, few subjects obtained greater than 80nmol/L, so future studies will need to utilize higher doses to confirm the estimated intakes.
Thread: Vitamin D - Estimated Intakes