Identification and quantitation of major carotenoids in selected components of the Mediterranean diet: green leafy vegetables, figs and olive oil

Objective: To characterize the carotenoid content of selected components of the Mediterranean diet commonly eaten by Greek migrants to Melbourne, a population group maintaining a traditional dietary regimen, and who exhibit relatively high circulating carotenoid concentrations and low cardiovascular disease mortality. Design and specimens: Opportunistic sampling of wild (sow thistle, amaranth, purslane and dandelion, collected from roadsides and home gardens) and commercially available (chicory, endive) green leafy vegetables and figs in season. Foods were selected on the basis that they are commonly eaten by Greek migrants but not by Anglo-Celtic persons, and had not previously been well-characterized with respect to their carotenoid contents. Extra virgin, cold-pressed olive oil and 'extra light' olive oil were obtained from commercial sources. Specimens were extracted with tetrahydrofuran (or chloroform: methanol for olive oil) and carotenoid contents were quantified using HPLC with UV detection. Two to six specimens of greens and figs were analysed. Dietary intake was assessed by food frequency questionnaire. Results: Wild green vegetables contained high concentrations of lutein (sow thistle > amaranth > purslane > dandelion) and beta-carotene (sow thistle > amaranth > purslane = dandelion). Sow thistle and amaranth contained lutein (15 and 13 mg/100 g, respectively) and beta-carotene (3.3 and 4.0 mg/100 g, respectively) at concentrations greater than that seen in the commercially available species of chicory and endive. Figs contained all major carotenoids appearing in plasma, albeit at low concentrations. Extra virgin cold-pressed olive oil contained substantial quantities of lutein and beta-carotene, but the more-refined 'extra light' olive oil did not. Conclusions: These components of the traditional Mediterranean diet contribute to the higher circulating concentrations of carotenoids in Greek migrants compared to Anglo-Celtic Australians. Sponsorship: This study largely funded by the National Health and Medical Research Council of Australia (grant no. 974098). Extra virgin olive oil donated by Picuba Foods, Marrickville, NSW, Australia.