Vitamin A equivalency and apparent absorption of β-carotene in ileostomy subjects using a dual-isotope dilution technique

Abstract

The objective was to quantify the vitamin A equivalency of -carotene in two diets using a dual-isotope dilution technique and the apparent β-carotene absorption as measured by the oral-faecal balance technique. Seventeen healthy adults with an ileostomy completed the 4-week diet-controlled, cross-over intervention study. Each subject followed both diets for 2 weeks: a diet containing vegetables low in β-carotene content with supplemental β-carotene in salad dressing oil (oil diet; mean β-carotene intake 3.1mg/d) and a diet containing vegetables and fruits high in β-carotene content (mixed diet; mean β-carotene intake 76mg/d). Daily each subject consumed a mean of 190g [13C10]-carotene and 195μg [13C10]retinyl palmitate in oil capsules. The vitamin A equivalency of β-carotene was calculated as the dose-corrected ratio of [13C5]retinol to [13C10]retinol in serum. Apparent absorption of β-carotene was determined with oral-faecal balance. Isotopic data quantified a vitamin A equivalency of [ 13C10]β-carotene in oil of 3.6:1 (95% CI 2.8, 4.6) regardless of dietary matrices differences. The apparent absorption of (labelled and dietary) β-carotene from the oil diet (30%) was 19-fold higher than from the mixed diet (16%). This extrinsic labelling technique can measure precisely the vitamin A equivalency of β-carotene in oil capsules, but it does not represent the effect of different dietary matrices. © 2010 The Authors.