Effect of Coca-Cola on Iron Absorption

Previous studies have suggested that Coca-Cola may enhance absorption of non-haem iron. A randomized cross-over trial will be undertaken to compare the absorption of iron added to a pizza meal consumed with either Coca-Cola, Diet Coke or mineral water. Pizza containing added iron, labelled with an iron stable isotope (Fe-58), will be consumed for lunch on two consecutive days with either a Coca-Cola, Diet Coke or mineral water drink. Iron absorption from the pizza will be determined using the erythrocyte incorporation technique. A baseline blood sample will be taken prior to consuming the first test meal (pizza + drink 1) and after approximately 15 days, a second fasting blood sample will be taken prior to consumption of a second set of test meals (pizza + drink 2). Iron isotope enrichment of the blood sample will be used as a baseline for the second set of test meals and to calculate absorption from the first set of test meals. A third blood sample will be taken after approximately 30 days and the iron isotope enrichment will be used as a baseline for the third set of test meals (pizza + drink 3) and to determine absorption from the second set of test meals. At about 45 days a final blood sample will be taken to determine absorption from the third set of test meals. Iron absorption will be calculated from the isotopic enrichment in blood, assuming that 80% of absorbed iron is incorporated into red blood cells. Absorption of iron consumed with Coca-Cola and Diet Coke will be compared with iron absorption when consumed with mineral water. The order in which the volunteers will be given the drinks will be randomised.