The study, published in Nutrition Journal, investigated whether genetic variation in vitamin D receptor proteins impacted the effects of supplementation with either vitamin D3 or vitamin D2 in a group of Thai participants.
Led by Hataikarn Nimitphong from Mahidol University, Thailand, the research team found that genetic variations in vitamin D receptor protein (DBP) has an effect on the vitamin D status - measured by total 25(OH)D - of those taking vitamin D3 supplements. However the genetic differences had no effect when vitamin D2 supplements were consumed.
"With D3 supplementation, subjects with CA or AA alleles had significantly less increase in 25(OH)D3 and total 25(OH)D when compared with those with the CC allele. However, no difference was found when the supplement was vitamin D2," explained the researchers.
"The present study demonstrated that DBP genetic variation is another factor which can influence the responsiveness to vitamin D supplementation," added Nimitphong and colleagues.
The research team gave 39 healthy participants 400 IU of either vitamin D3 or D2, plus a calcium supplement, every day for three months. Total serum 25(OH)D, 25(OH)D3 and 25(OH)D2 were measured in addition to individual genotyping of the DBP gene.
Supplementation with vitamin D3 supplementation at 400 IU per day was found to increase 25(OH)D3 significantly, while supplementation with vitamin D2 led to a similar increase in 25(OH)D2 levels in addition to a decrease of 25(OH)D3.
After three months participants given vitamin D3 tended to have higher total 25(OH)D levels than those consuming vitamin D2, Nimitphong and colleagues said.
The team then classified al 39 participants by the genetic makeup of their DBP gene, analysing those with a normal homozygous allele (CC) with other types of allele (CA or AA) - finding that participants with CA or AA alleles did not increase 25(OH)D3 and total 25(OH)D as much as those who possessed the CC allele when given supplements of vitamin D3 supplements.
"Genetic variation in vitamin D binding protein (rs4588 SNP) influences responsiveness to vitamin D3 but not vitamin D2," the team said.
Source: Nutrition Journal
Published online ahead of print, doi: 10.1186/1475-2891-12-39
"Changes in circulating 25-hydroxyvitamin d according to vitamin D binding protein genotypes after vitamin D3 or D2 supplementation"
Authors: Hataikarn Nimitphong, Sunee Saetung, Suwannee Chanprasertyotin, La-or Chailurkit, Boonsong Ongphiphadhanakul