Milk Enhances In Vitro Accessibility and Fractional Absorption of Zinc (FAZ) from High Phytate Intrinsically Labelled Rice in Humans

Zn absorption is hampered by phytate (PA), which is present in large amounts in plant-based foods. We aimed to assess in vitro Zn accessibility at various PA/Zn molar ratios, as well as fractional absorption of Zn from partially polished intrinsically labelled rice with and without the addition of milk in humans. Triplicate samples of steamed white rice were blended with water, raw milk or UHT milk, and incubated for 4 hrs in the absence or presence of PA, and Zn content in the supernatant was assessed. Female subjects (n=18) were given 90 g of steamed rice that was intrinsically labelled with 67Zn (75%), either with water or milk in a cross-over design with a 1-month washout period. Both meals contained the same amount of Zn. An intravenous infusion dose of 0.02 mg 70Zn in saline was given half-way each meal. FAZ was determined from isotope ratios measured in spot urine samples collected 4 days after consumption of the rice meal. UHT milk and raw milk showed a significantly higher extraction of Zn from white rice in comparison to water at PA/Zn molar ratios of 15 and 30. In human subjects, FAZ from rice was 13.4% (SD 3.8) from rice consumed with water (n=18) and 21.7% (SD 4.0) from rice consumed with milk (n=17; paired t-test, P