Vitamin A equivalency of β-carotene in healthy adults: limitation of the extrinsic dual-isotope dilution technique to measure matrix effect

Abstract

Data on the vitamin A equivalency of b-carotene in food are inconsistent. We quantified the vitamin A equivalency (mg) of b-carotene in two diets using the dual-isotope dilution technique and the oral-faecal balance technique. A diet-controlled, cross-over intervention study was conducted in twenty-four healthy adults. Each subject followed two diets for 3 weeks each: a diet containing vegetables low in b-carotene with supplemental b-carotene in salad dressing oil ('oil diet') and a diet containing vegetables and fruits high in b-carotene ('mixed diet'). During all 6 weeks, each subject daily consumed a mean of 55 (SD 0·5) mg [

Vitamin A equivalence of the β-carotene in β-carotene–biofortified maize porridge consumed by women

“…According to the guidelines, when ingested in low amounts (,2 mg), 2 lg b-carotene in oil is equivalent to 1 lg retinol. Investigators who used liquid chromatography-mass spectroscopy to study the bioconversion of small 13 C-labeled b-carotene doses in oil in healthy adults reported similar vitamin A equivalence values of 2.4:1 (40) and 3.4:1 (41). A limitation of our method is that the retinyl palmitate measured in the plasma TRL fractions reflects only the bioconversion of b-carotene in the intestine.…”

Methods for Assessing Aspects of Carotenoid Bioavailability

“…Cambridge Isotope Laboratory (Andover, MA, USA) and ARC Laboratories (Apeldoorn, the Netherlands). Stable isotopes are typically detected with sophisticated and expensive mass spectrometry techniques, including HPLC-MS [287,295,297,298,308], HPLC-MS-MS [305], or, for highest sensitivity for femtomole range detection, accelerator mass spectrometry [234]. However, an HPLC method to separate 2 H8beta-carotene, has been reported, while separation of 2 H6beta-carotene from beta-carotene was not successful [305], explained by increased polarity when carrying deuterated atoms.…”

“…As a consequence, with using recent state of the art techniques, the earlier drawback of stable isotopes requiring large doses for sufficient sensitivity is dwindling. Thus, doses as low as 55 μg 13 C10betacarotene were administered when using HPLC-MS [308], and HPLC-MS-MS [305], and amounts as low as 1 nmol Clabeled (both radioactive or not) beta-carotene by using accelerator-MS [300] can be employed. Using stable isotope techniques, TRL-AUC fraction for beta-carotene has been investigated [309] to demonstrate that free and plant sterol esters can have a negative impact on carotenoid absorption, as has been compartment modeling for studying beta-carotene utilization [48].…”

“…Extrinsic labels simply, such as labeled carotenoid standards added in pure form and blended with the test meal on the other hand could work for simple matrices such as food supplements, assuming equilibrium between the added carotenoids and carotenoids normally or natively present, are more affordable, can be dosed easily, but do not account for more complex matrix binding effects. Nevertheless, a number of studies have been conducted, investigating uptake and distribution of carotenoids dissolved in oil ingested together with a the test meal [287,300,305,308].…”

Recent progress in stable isotope methods for assessing vitamin metabolism

“…Recently it was shown that diet had no effect on the bioefficacy of b-carotene taken in oil as a supplement [49 ] and, therefore, the 'extrinsic dual-isotope dilution' method could not assess the effect of food matrices. However, the combination of intrinsic labelling and stable isotopes has been used to measure the bioefficacy of b-carotene from spinach as 0.11 for healthy Chinese men [50] and 0.10 for children [51].…”