Oral vitamin D - Is it necessary to be taken with meals containing fat?

Abstract

Vitamin D is fat-soluble. It is suggested to be taken with meals containing fat to enhance its intestinal absorption. However, there are only a few controlled studies which investigate prandial inferences on its absorption.
Within a group of 13 general practitioners, during a period of three months, we ran two identical study protocols during winter and early springtime. Blood was taken from the subjects, 60’000 units of vitamin D (cholecalciferol) in 3 ml of oil was ingested, and blood was sampled once again a week later. In a randomized cross-over design, one time the vitamin was ingested postprandially, and another time in a fasting state.
The basal levels of 25-hydroxyvitamin D were 45 (28) (median, interquartile range) before fasting, and 40 (15) nmol/l before postprandial dosing. One week thereafter, serum 25-hydroxyvitamin D was increased by 13 (21), when the supplement was ingested in a fasting state, while taken after a meal containing fat, the rise was 25 (17) nmol/l (n.s., p=0.13). The other parameters which were tested remained unchanged throughout the study: calcium, phosphate, albumin, and 1,25?dihydroxyvitamin D (calcitriol).
Our preliminary data do not support major influences on vitamin D absorption by the influence of fasting vs. concomitant fatty meal intake. Vitamin D oral loading doses can be applied irrespective of prandial state, while its maintenance dosing by the patients should still take place after a meal containing fat. Absorption of vitamin D seems to be unpredictable – fractionate dosage and determination of 25-hydroxyvitamin D during treatment may be helpful. Unexplained low serum levels after repeated supplementation could be due to intestinal disease, mainly celiac.