No influence of supplemental dietary calcium intake on the bioavailability of spinach carotenoids in humans

Dietary carotenoid intake, especially from fruits and vegetables, has been associated with a reduced incidence of several chronic diseases. However, its bioavailability can vary, depending on the food matrix and host factors. Recently, it has been suggested that divalent minerals negatively impinge on carotenoid bioavailability by reducing bile-salt and non-esterified fatty-acid levels in the gut, which normally aid in emulsifying carotenoids. The aim of the present study was to investigate whether supplemental Ca would negatively influence carotenoid absorption in humans. A total of twenty-five healthy, non-obese men (age: 20–46 years, BMI<30 kg/m2) were recruited for this postprandial, randomised, crossover, double-blinded trial. Following a randomised block design, each participant received (after 2-week washout periods), on three occasions separated by 1 week, 270 g of spinach-based meals (8·61 (sd 1·08) mg carotenoids/100 g fresh weight), supplemented with 0, 500 or 1000 mg of Ca (as calcium carbonate), with each participant acting as his or her own control. Blood samples were collected at regular postprandial intervals for up to 10 h following test meal intake, and standardised lunches were served. TAG-rich lipoprotein fractions were separated and carotenoid concentrations determined. AUC for meals without supplemented Ca were 22·72 (sem 2·78) nmol×h/l (lutein), 0·19 (sem 3·90) nmol×h/l (β-carotene) and 2·80 (sem 1·75) nmol×h/l (β-cryptoxanthin). No significant influence of supplementation with either 500 or 1000 mg of supplemental Ca was found. In conclusion, Ca – the most abundant divalent mineral in the diet – given at high but physiological concentrations, does not appear to have repercussions on the bioavailability of carotenoids from a spinach-based meal.