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Despite interest in the health-beneficial role of carotenoids little is known about the specific storage metabolism and mechanisms involved in various target tissues. The aim of the study was to search for a relatively simple non-invasive method to detect and determine the cellular effects of supplemented dosage of beta-carotene and lycopene to peripheral tissues such as the buccal mucosa in relation to the plasma concentrations. Subjects (30) were allocated into five different subgroups of 6 volunteers. The change in concentration of all-trans-beta-carotene and lycopene in plasma and in buccal mucosal cells was measured in groups of volunteers supplemented with either 15 mg, 30 mg or placebo capsules in a randomised double blind study for a period of 7 days. With the exception of supervised high fat (40 g carotenoid free sunflower oil) breakfasts and capsule ingestion the volunteers ate their habitual diets. Plasma lycopene and beta-carotene concentrations were determined at baseline and following one week of capsule ingestion. In all the supplemented groups the plasma carotenoid levels were significantly higher than in the placebo group indicating absorption of the supplement. Carotenoid concentrations, expressed per unit protein, assayed in buccal mucosal cells before (at baseline) and at the end of the study were found to be significantly higher in the groups supplemented at 30 mg/d, of either carotenoid as compared to the 15 mg/d or placebo supplemented groups. We conclude that buccal mucosal cells respond readily to changes in plasma beta-carotene and lycopene concentration. These observations suggest that dietary carotenoids are quickly incorporated into rapidly turning over mucosal tissues. It is not clear if the change in carotenoid content of the plasma is reflected in existing cells or only in those concurrently produced during the elevated plasma concentration. If desquamated buccal mucosal cells reflect habitual plasma carotenoid concentration then it is not an appropriate tissue for the measurement of acute changes.