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Astaxanthin is a marine carotenoid that has a number of potential health benefits, including a very strong antioxidant potential. Present in the flesh of salmonids and shellfish, its natural sources currently on the market for food supplements come from the algae Haematococcus pluvialis and krill. However other natural sources can be found and may be of interest. Cellular uptake studies were performed on Caco-2/TC7 colonic cells. The cells were cultured on a semi-permeable membrane to create a polarized and functional epithelium, representative of the intestinal barrier. Four sources of astaxanthin were selected and compared; synthetic, natural extracts from bacteria, algae or yeast. Astaxanthin was incorporated at a concentration of 5µM into mixed micelles and applied to cultured cells and concentration of astaxanthin measured by HPLC in both apical and basolateral compartments. Small variations in bioavailability were observed at 3 hours. After 6 hours, only the algae source of astaxanthin was still present in the apical compartment as the esterified form. Structure-activity relationships are further discussed. Animal experiments using yeast and algae sources in different types of matrices confirm the role of source and formulation in the bioavailability potential of astaxanthin.