The food matrix of spinach is a limiting factor in determining the bioavailability of beta-carotene and to a lesser extent of lutein in humans

Carotenoid bioavailability depends, amongst other factors, on the food matr ix and on the type and extent of processing. To examine the effect of vario usly processed spinach products and of dietary fiber on serum carotenoid co ncentrations, subjects received, over a 3-wk period, a control diet (n = 10 ) or a control diet supplemented with carotenoids or one of four spinach pr oducts (n = 12 per group): whole leaf spinach with an almost intact food ma trix, minced spinach with the matrix partially disrupted, enzymatically liq uefied spinach in which the matrix was further disrupted and the liquefied spinach to which dietary fiber (10 g/kg wet weight) was added. Consumption of spinach significantly increased serum concentrations of all-trans-beta-c arotene, cis-beta-carotene, (and consequently total beta-carotene), lutein, alpha-carotene and retinol and decreased the serum concentration of lycope ne, Serum total beta-carotene responses (changes in serum concentrations fr om the start to the end of the intervention period) differed significantly between the whole leaf and liquefied spinach groups and between the minced and liquefied spinach groups. The lutein response did not differ among spin ach groups. Addition of dietary fiber to the liquefied spinach had no effec t on serum carotenoid responses, The relative bioavailability as compared t o bioavailability of the carotenoid supplement for whole leaf, minced, liqu efied and liquefied spinach plus added dietary fiber for beta-carotene was 5.1, 6.4, 9.5 and 9.3%, respectively, and for lutein 45, 52, 55 and 54%, re spectively. We conclude that the bioavailability of lutein from spinach was higher than that of beta-carotene and that enzymatic disruption of the mat rix (cell wall structure) enhanced the bioavailability of beta-carotene fro m whole leaf and minced spinach, but had no effect on lutein bioavailabilit y.