Endocrine Abstracts

Introduction: Vitamin D insufficiency (25-hydroxy vitamin D <50 nmol/l) is a global health problem. Vitamin D food fortification might be the solution, but knowledge is sparse on whether fortification of various food items affects the bioavailability differently. It is generally assumed that ingesting vitamin D with a fatty meal improves the bioavailability of vitamin D. Furthermore, complex formation with whey protein isolate (WPI) may enhance the stability of vitamin D and thereby improve bioavailability. We studied the efficiency of fortifying different food items with vitamin D₃.

Materials and methods: In a randomised, multiple (5-periods), crossover trial, we enrolled 30 postmenopausal women with vitamin D insufficiency aged 60-80 years. We measured immediate changes in plasma concentrations of cholecalciferol (D₃ ) in response to intake of different food matrices with 200 µg D₃ added i.e., 1) 500 mL of water, 2) 500 mL of milk, 3) 500 mL of juice, 4) 500 mL of juice with D3 complex-bound to WPI, and 5) 500 mL of water without D₃ (placebo). The different food matrices were provided in a randomised order with at least ten days washout period in-between study days. On each study day, blood samples were collected at 0 h, 2 h, 4 h, 6 h, 8 h, 10 h, 12 h and 24 h.

Results: Complexation D₃ -WPI in apple juice did not enhance maximum concentration (Cmax) of serum D₃ compared to juice without WPI (25 nmol/l vs 24 nmol/l; P=0.61), nor the area under the time-D₃ curve (AUC) (370 nmol/l *24 h vs 357 nmol/l *24 h; P=0.93). However, compared to juice, Cmax and AUC of serum D₃ were significantly higher in response to intake of milk (30 nmol/l and 452 nmol/l *24 h) and water with D₃ added (32 nmol/l and 479 nmol/l *24 h) (P<0.05, all). No difference in serum D₃ was observed between milk and water (P=0.29, Cmax; P=0.33, AUC).

Conclusion: The bioavailability of D₃ assessed by Cmax and AUC was superior in water and milk compared to juice, independent of whether complexation D₃ -WPI was added to juice.