Effects of vitamin D2-fortified breadv. supplementation with vitamin D2or D3on serum 25-hydroxyvitamin D metabolites: an 8-week randomised-controlled trial in young adult Finnish women
AbstractThere is a need for food-based solutions for preventing vitamin D deficiency. Vitamin D3(D3) is mainly used in fortified food products, although the production of vitamin D2(D2) is more cost-effective, and thus may hold opportunities. We investigated the bioavailability of D2from UV-irradiated yeast present in bread in an 8-week randomised-controlled trial in healthy 20–37-year-old women (n33) in Helsinki (60°N) during winter (February–April) 2014. Four study groups were given different study products (placebo pill and regular bread=0 µg D2or D3/d; D2supplement and regular bread=25 µg D2/d; D3supplement and regular bread=25 µg D3/d; and placebo pill and D2-biofortified bread=25 µg D2/d). Serum 25-hydroxyvitamin D2(S-25(OH)D2) and serum 25-hydroxyvitamin D3(S-25(OH)D3) concentrations were measured at baseline, midpoint and end point. The mean baseline total serum 25-hydroxyvitamin D (S-25(OH)D=S-25(OH)D2+S-25(OH)D3) concentration was 65·1 nmol/l. In repeated-measures ANCOVA (adjusted for baseline S-25(OH)D as total/D2/D3), D2-bread did not affect total S-25(OH)D (P=0·707) or S-25(OH)D3(P=0·490), but increased S-25(OH)D2compared with placebo (P<0·001). However, the D2supplement was more effective than bread in increasing S-25(OH)D2(P<0·001). Both D2and D3supplementation increased total S-25(OH)D compared with placebo (P=0·030 andP=0·001, respectively), but D2supplementation resulted in lower S-25(OH)D3(P<0·001). Thus, D2from UV-irradiated yeast in bread was not bioavailable in humans. Our results support the evidence that D2is less potent in increasing total S-25(OH)D concentrations than D3, also indicating a decrease in the percentage contribution of S-25(OH)D3to the total vitamin D pool.