In vitro accessibility and intake of beta-carotene from cooked green leafy vegetables and their estimated contribution to vitamin A requirements.

Provitamin A carotenoids from green leafy vegetables constitute a major dietary source of vitamin A in Tanzania. The efficiency of different vegetable preparations in contributing to the daily safe intake level of vitamin A for children was evaluated in the present study. The amount of bioaccessible (available for absorption) all-trans-beta-carotene from green leafy vegetable dishes prepared either traditionally in households or with an improved method was estimated by an in vitro digestion method that simulates human digestion. The median vegetable portion size consumed by 34 children (2-12 years old) in the surveyed households was determined by weighing. The amount of all-trans-beta-carotene available for absorption from the same type of vegetables cooked without oil by traditional or a modified method ranged from 5 to 12% and 4 to 15%, respectively. Vegetables cooked with modified method with oil had 2-5 times higher amount of in vitro accessible all-trans-beta-carotene than vegetables cooked without oil. A median portion (84 g) of such a relish then provided 88-477% of the daily safe intake level of vitamin A, while portions cooked without oil only provided between 23 and 46%. In this study, a wide variation in all-trans-beta-carotene content and bioaccessibility among studied green leaves was obtained. Still, to supply daily safe intake level of vitamin A for children from a median vegetable relish portion it is necessary to add oil in the preparation.