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.

Inclusion criteria

• Women
• Age > 18 and < 65

Exclusion criteria

• Men
• Age < 18 or > 65
• BMI <18.5 or > 35
• Serum ferritin value of <12 or >50µg/L (±10% to allow for day to day and analytical variation)
• Volunteers will be excluded if they are found to have depressed or elevated blood pressure measurements (<90/50 or <95/55 if symptomatic or >160/100)
• Diagnosed with a long-term illness requiring active treatment, e.g. diabetes, cancer, cardiovascular disease.
• Gastrointestinal disease (excluding hiatus hernia unless symptomatic or study intervention/procedure is contraindicated)
• Regular prescribed medication that may interfere with iron metabolism
• Regular use of antacids and laxatives (at least once a week)
• Women who are pregnant or less than 12 months since giving birth
• Women breast feeding
• Vitamin supplements with or without minerals if taken more than once a week, and unwillingness to discontinue occasional use for the duration of study
• Unwillingness to discontinue use of herbal supplements for the duration of study
• Use of antibiotics within four weeks prior to study start
• Parallel participation in another study which involves dietary interventions or sampling of blood that may increase the volume taken above 500ml in a 4-month period
• Asthma requiring treatment within the last two years
• Results of clinical screening which indicate, or are judged by the HNU Medical Advisor to be indicative of a health problem which could compromise the well-being of the volunteer if they participated or which would affect the study data.
• Allergy to any of the ingredients in the test meals