Vitamin-D2 treatment-associated decrease in 25(OH)D3 level is a reciprocal phenomenon: a randomized controlled trial

Abstract

Background: Vitamin-D2 (D2) treatment has been associated with a decrease in 25-hydroxy (25(OH)) vitamin-D3 (D3) level, suggesting that D3 treatment would be preferred to raise total 25(OH) vitamin-D (D) level. We postulated that D2 treatment-associated decrease in 25(OH)D3 level is related to the increase in 25(OH)D level rather than being D2-specific, and thus there would be a similar D3 treatment-associated decrease in 25(OH)D2 level.

Methods: Fifty volunteers were block-randomized to 50,000 IU D2 or placebo orally once (study-1) and fifty volunteers received 50,000 IU D2 orally once and 4 days later block-randomized to 50,000 IU D3 or placebo orally once (study-2). Interventions were concealed from volunteers and research coordinators and blindly-administered. Serum 25(OH)D2 and 25(OH)D3 levels were blindly-determined at baseline and days 14, 28, 42, and 56, post-randomization by high performance liquid chromatography assay. Results of 97 participants were analyzed. Primary outcome measure was day-28 D2-associated change in 25(OH)D3 level in study-1 and D3-associated change in 25(OH)D2 level in study-2, adjusted for baseline levels.

Results: Mean (95% confidence interval) difference between the active and placebo arms in the decrease in day-28 25(OH)D3 (study-1) and 25(OH)D2 (study-2) levels was 13.2 (9.7 to 16.6) and 9.8 (5.2 to 14.4) nmol/L, respectively. Corresponding differences at day-56 were 10.8 (6.8 to 14.8) and 1.7 (- 7.6 to 11.1) nmol/L, respectively. The difference between the placebo and active arms in area-under-the-curve at day-28 (AUC₂₈) and day-56 (AUC₅₆) were 262.3 (197.8 to 326.7) and 605.1 (446.3 to 784.0) for 25(OH)D3 (study-1) and 282.2 (111.2 to 453.3) and 431.2 (179.3 to 683.2) nmol.d/L for 25(OH)D2 (study-2), respectively. There were significant correlations between day-28 changes in 25(OH)D2 and 25(OH)D3 levels in study-1 (rho = - 0.79, p < 0.001) and study-2 (rho = - 0.36, p = 0.01), and between day-28 changes in 25(OH)D2 level and baseline 25(OH)D level in study-2 (rho = - 0.42, p = 0.003).

Conclusions: Compared to placebo, D3 treatment is associated with a decrease in 25(OH)D2 level similar in magnitude to D2-treatment associated decrease in 25(OH)D3 level; however, the D3-placebo difference in 25(OH)D2 level is shorter-lasting. Changes in 25(OH)D2 and 25(OH)D3 levels are correlated with each other and with baseline 25 (OH) D levels, suggesting a common regulatory mechanism.

Trial registration: ClinicalTrial.gov identifier: NCT03035084 (registered January 27, 2017).

Keywords: 25-hydroxyvitamin D2 level; 25-hydroxyvitamin D3 level; Cholecalciferol treatment; Ergocalciferol treatment.

Fig. 1

Participants flow chart. One participant was excluded because of formula failure/not ingesting D2 dose (study-1, D2 arm), one withdrew for personal reasons (study-2, D3 arm), and one was excluded because of high 25(OH)D2 before receiving the 50,000 IU D2 loading dose (study-2, D3 arm)

Fig. 2

Changes in 25(OH)D2 and 25(OH)D3 levels over 56 days. Data represent mean levels. Error bars represent standard errors of the mean. a and b, study-1: participants were randomized to a single oral dose of 50,000 IU D2 (red squares) or placebo (blue diamond). c and d, study-2: participants were randomized to a single oral dose of 50,000 IU D3 (red squares) or placebo (blue diamond) four days after receiving a single oral dose of 50,000 IU D2. 25(OH)D2, 25-hydroxyvitamin D2. 25(OH)D3, 25-hydroxyvitamin D3. D0, D14, D28, D42, and D56 are day of randomization, and 14, 28, 42, and 56 days after randomization, respectively

Fig. 3

Decrease in 25(OH)D2 and 25(OH)D3 levels from randomization to day-28 (a and c) or day-56 (b and d). Bars represent means and standard errors. a and b, study-1: participants were randomized to a single oral dose of 50,000 IU D2 (solid bars) or placebo (open bars). c and d, study-2: participants were randomized to a single oral dose of 50,000 IU D3 (solid bars) or placebo (open bars) four days after receiving a single oral dose of 50,000 IU D2. 25(OH)D2, 25-hydroxyvitamin D2. 25(OH)D3, 25-hydroxyvitamin D3. *, p < 0.001

Fig. 4

25(OH)D2 and 25 (OH) D3 area-under-the-curves from randomization to day-28 (AUC₂₈) or day-56 (AUC₅₆). Bars represent means and standard errors. a and b, study-1: participants were randomized to a single oral dose of 50,000 IU D2 (solid bars) or placebo (open bars). c and d, study-2: participants were randomized to a single oral dose of 50,000 IU D3 (solid bars) or placebo (open bars) four days after receiving a single oral dose of 50,000 IU D2. 25(OH)D2, 25-hydroxyvitamin D2. 25(OH)D3, 25-hydroxyvitamin D3. *, p < 0.001. **, p < 0.005

Fig. 5

Correlation between changes in day-28 25(OH)D2 and 25(OH)D3 levels and baseline total 25(OH)D level. a and b, study-1: participants were randomized to a single oral dose of 50,000 IU D2 or placebo. c and d, study-2: participants were randomized to a single oral dose of 50,000 IU D3 or placebo four days after receiving a single oral dose of 50,000 IU D2. 25(OH)D2, 25-hydroxyvitamin D2. 25(OH)D3, 25-hydroxyvitamin D3. 25(OH)D, total 25-hydroxyvitamin D. a, rho = − 0.79 (CI, − 0.66 to − 0.88), p < 0.001. b, rho = − 0.17 (CI, 0.12 to − 0.43), p = 0.31. c, rho = − 0.36 (CI, − 0.09 to − 0.58), p = 0.01. d, rho = − 0.42 (CI, − 0.15 to − 0.63), p = 0.003