Cellular transport of lutein is greater from uncooked rather than cooked spinach irrespective of whether it is fresh, frozen, or canned Laurie O'Sullivan, Lisa Ryan, S. Aisling Aherne, Nora M. O'Brien ⁎ Department of Food and Nutritional Sciences, University College Cork, Cork, Republic of Ireland Received 7 January 2008; revised 26 May 2008; accepted 28 May 2008 Abstract Lutein, a carotenoid found in significant levels in spinach, has attracted a great deal of attention owing to its reported function as a shield against the photooxidative effects of blue light. Therefore, the rationale of this study was to examine the effects of various processing and cooking methods on lutein bioavailability from spinach (Spinacia oleracea) using an in vitro digestion procedure coupled with the use of a human intestinal Caco-2 cell model. Fresh, frozen, and canned spinach were analyzed uncooked and after boiling or microwave cooking. Lutein content from the uncooked and cooked digested food (digestate) and appropriate micelles was determined. Micellarized lutein from the spinach samples was adjusted to 0.1 μmol/L and added to Caco-2 cells. Cellular uptake and secretion (cellular transport) of lutein were determined. Our results showed that digestate obtained from uncooked canned spinach had greater lutein content (P b .05) than uncooked fresh or frozen spinach. Microwave cooking, but not boiling, significantly lowered the lutein content of canned spinach digestate and micelles compared with their uncooked counterparts. Interestingly, there were no differences in the micellarization of lutein between the cooking and processing methods. Cellular transport of lutein was greater from uncooked spinach micelles compared with boiled or microwave- cooked spinach. To conclude, although the lutein content of digesta and micelles may have been modified, its micellarization was not significantly affected by any of the cooking or processing methods tested. In general, cellular transport of lutein was greatest in uncooked spinach irrespective of whether the spinach was fresh, frozen, or canned. © 2008 Elsevier Inc. All rights reserved. Keywords: Bioavailability; Carotenoid; Caco-2 cells; Digestion; In vitro; Lutein; Micelles; Spinach (Spinacia oleracea) Abbreviations: HBSS, hanks balanced salt solution; HPLC, high-performance liquid chromatography. 1. Introduction The xanthophyll carotenoid lutein is present in significant amounts in the macular tissue and lens of the eye where it is thought to function as an antioxidant and a shield against the photooxidative effects of blue light [1-4]. In addition, high dietary intake of lutein has been associated with reduced risks of certain cancers, coronary heart disease, and stroke [5]. Rich dietary sources of lutein include green leafy vegetables such as spinach (Spinacia oleracea), which is reported to contain 6.3 mg of lutein per 100 g [6]. In the past number of years, there has been an increasing body of research conducted on lutein; however, limiting data exist on the impact of processing (eg, freezing and canning) and domestic cooking on both the bioavailability and bioacces- sibility of this carotenoid. Bioavailability is termed as the fraction of an ingested nutrient available for use in normal physiologic functions and storage in the body [7]. There are a number of steps involved in the bioavailability of carotenoids from foods. These include (1) the release of carotenoids from a food matrix, (2) the transfer of carotenoids to micelles, (3) the uptake of carotenoids by intestinal cells, (4) the incorpora- tion of carotenoids into chylomicrons and their secretion by intestinal cells, and (5) the transport of carotenoids to the Available online at www.sciencedirect.com Nutrition Research 28 (2008) 532 – 538 www.nrjournal.com ⁎ Corresponding author. Tel.: +353 21 4902884; fax: +353 21 4270244. E-mail address: nob@ucc.ie (N.M. O'Brien). 0271-5317/$ – see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.nutres.2008.05.011