Bioavailability of β-carotene is lower in raw than in processed carrots and spinach in women

Abstract

Populations at risk of vitamin A deficiency usually rely on dietary provitamin A carotenoids to meet vitamin A needs, yet bioavailability of these compounds is influenced by several factors as follows: location in the plant source, the presence of other influencing dietary components, and type and extent of processing. The purpose of this study was to examine the plasma β-carotene response to raw vs. processed carrots and spinach. Subjects were eight healthy females aged 23-36 y who consumed ~9.3 mg β-carotene daily from either raw or thermally processed and pureed vegetables in two 4-wk treatment periods in a crossover study. Plasma concentrations of total, all- trans-, and cis-β-carotene and α-carotene were measured at base line and the end of each treatment period by using HPLC assays. Total and all-trans (but not cis) plasma β-carotene concentrations were significantly greater than base-line concentrations in the processed feeding period (P < 0.04) and tended to be greater in the raw feeding period (P = 0.08). Daily consumption of processed carrots and spinach over a 4-wk period produced an increase in plasma β-carotene concentration that averaged three times that associated with consumption of the same amount of β-carotene from these vegetables in the raw form (P = 0.09). Increased cis isomers provided in the processed vegetables did not result in significantly greater plasma cis-β-carotene isomer concentrations. These results suggest that isomerization of β- carotene by heat treatment does not negate the enhanced β-carotene uptake associated with consuming commercially processed vegetables compared with raw vegetables.