OBJECTIVES: Vitamin D insufficiency (blood 25-hydroxyvitamin D <50 nmol/L) is a global health problem. Vitamin D food fortification might be a solution, but knowledge is sparse on which food matrices yield the highest bioavailability. The aim of this study was to investigate the influence of different food matrices including complex formations with whey proteins on the human bioavailability of vitamin D.

METHODS: In this randomized, multiple crossover trial, we enrolled 30 postmenopausal women 60 to 80 y of age with vitamin D insufficiency. We measured changes in serum concentrations of vitamin D3 (D3) postprandially for 24 h in response to the intake of 500 mL of different food matrices with 200 µg D3 added compared with a control (500 mL of water). Foods included apple juice with whey protein isolate (WPI), apple juice, semi-skim milk, and water (with D3). The food matrices were provided in a randomized order with ≥10-d washout period between them. On each intervention day, blood samples were collected at 0, 2, 4, 6, 8, 10, 12 and 24 h.

RESULTS: D3 with WPI in juice did not enhance area under the curve (AUC) of serum D3 compared with juice without WPI (370 nmol × 24 h/L; 95% confidence interval [CI], 321-419 versus 357 nmol × 24 h/L; 95% CI, 308-406 nmol × 24 h/L; P = 0.65). However, compared with juice, the AUC was significantly higher in response to the intake of D3 in milk (452 nmol × 24 h/L; 95% CI, 402-502 nmol × 24 h/L) and water with D3 (479 nmol × 24 h/L; 95% CI, 430-527 nmol × 24 h/L; P < 0.05). No difference was observed between milk and water (P = 0.34).

CONCLUSIONS: The bioavailability of D3 was superior in milk and water compared with juice, regardless of whether WPI was added.