A liquid chromatography-mass spectrometry method for the quantification of bioavailability and bioconversion of beta-carotene to retinol in humans

A method based on high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (APCI LC-MS) was developed for the quantification of the bioavailability of retinyl palmitate and beta-carotene and the bioconversion of beta-carotene to retinol in humans. Following oral administration of [8,9,10,11,12,13,14,15,19,20-13C10]-retinyl palmitate and [12,13,14,15,20,12',13',14',15',20'-13C10]-beta-carotene at physiological doses to children between 8 and 11 years of age, blood samples were drawn and serum was prepared. Retinol and beta-carotene were extracted from 0.2- and 1.0-mL serum samples, respectively, and analyzed using reversed-phase HPLC with a C30 column interfaced to an APCI mass spectrometer. Unlike other LC-MS assays for carotenoids, no additional purification steps were necessary, nor was any derivatization of retinol or beta-carotene required. APCI LC-MS showed a linear detector response for beta-carotene over 4 orders of magnitude. Using selected ion monitoring to record the elution profile of protonated circulating beta-carotene at m/z 537 and [13C10]-beta-carotene at m/z 547, the limit of detection was determined to be 0.5 pmol injected on-column. To assess the ratio of labeled to unlabeled retinol, selected ion monitoring was carried out at m/z 269, 274, and 279. These abundant fragment ions corresponded to the loss of water from the protonated molecule of circulating retinol, [13C5]-retinol (metabolically formed from orally administered [13C10]-beta-carotene), and [13C10]-retinol (formed by hydrolysis of [13C10]-retinyl palmitate). The ratios of labeled to unlabeled retinol and the ratio of labeled to unlabeled beta-carotene were calculated. Combined with standard HPLC measurement of beta-carotene and retinol concentration and a mathematical model, these results showed that this simple LC-MS method can be used to quantify beta-carotene bioavailability and its bioconversion to retinol at physiologically relevant doses.     

Orange fruit is more effective than are dark-green, leafy vegetables in increasing serum concentrations of retinol and beta-carotene in schoolchildren in Indonesia

The objectives of this study were to quantify the effectiveness of dietary retinol sources, orange fruit, and dark-green, leafy vegetables in improving vitamin A status, and to test whether orange fruit is a better source of vitamin A and carotenoids than are leafy vegetables. Anemic schoolchildren aged 7-11 y (n = 238) in West Java, Indonesia, were randomly allocated to 1 of 4 groups to consume 2 complete meals/d, 6 d/wk, for 9 wk: 1) 556 retinol equivalents (RE)/d from retinol-rich food (n = 48); 2) 509 RE/d from fruit (n = 49); 3) 684 RE/d from dark-green, leafy vegetables and carrots (n = 45); and 4) 44 RE/d from low-retinol, low-carotene food (n = 46). Mean changes in serum retinol concentrations of the retinol-rich, fruit, vegetable, and low-retinol, low-carotene groups were 0.23 (95% CI: 0.18, 0.28), 0.12 (0.06, 0.18), 0.07 (0.03,0.11), and 0.00 (-0.06, 0.05) micromol/L, respectively. Mean changes in serum beta-carotene concentrations in the vegetable and fruit groups were 0.14 (0.12, 0.17) and 0.52 (0.43, 0.60) micromol/L, respectively. Until now, it has been assumed that 6 microg dietary beta-carotene is equivalent to 1 RE. On the basis of this study, however, the equivalent of 1 RE would be 12 microg beta-carotene (95% CI: 6 microg, 29 microg) for fruit and 26 microg beta-carotene (95% CI: 13 microg, 76 microg) for leafy vegetables and carrots. Thus, the apparent mean vitamin A activity of carotenoids in fruit and in leafy vegetables and carrots was 50% (95% CI: 21%, 100%) and 23% (95% CI: 8%, 46%) of that assumed, respectively. This has important implications for choosing strategies for controlling vitamin A deficiency. Research should be directed toward ways of improving bioavailability and bioconversion of dietary carotenoids, focusing on factors such as intestinal parasites, absorption inhibitors, and food matrixes.     

Reappraisal of the role of vegetables in the vitamin A status of mothers in Central Java, Indonesia

Food-based approaches for controlling vitamin A deficiency and its consequences, such as increased mortality, more severe morbidity, and anemia, have become increasingly important, thus prompting a reassessment of the relation between vitamin A intake and status. A nutrition surveillance system in Central Java, Indonesia, assessed the vitamin A intake and serum retinol concentration of women with a child < or =24 mo old with a semiquantitative 24-h recall method that categorized vitamin A-containing foods into 3 categories of plant foods and into 2 categories of animal foods and identified portions as small, medium, or large. Median vitamin A intake was 335 retinol equivalents (RE)/d (n = 600) and vitamin A intake from plant foods was 8 times higher than from animal foods. Serum retinol concentration was related to vitamin A intake in a dose-response manner. The multiple logistic regression model for predicting the chance for a serum retinol concentration greater than the observed median (> or = 1.37 micromol/L) included physiologic factors, vitamin A intake from plant [odds ratio (95% CI) per quartile: 1st, 1.00: 2nd, 1.23 (0.75, 2.02); 3rd, 1.60 (0.97, 2.63); and 4th, 2.06 (1.25, 3.40)] and animal [1st and 2nd, 1.00; 3rd, 1.31 (0.86, 2.02); and 4th, 2.18 (1.40. 3.42)] foods, home gardening [(no, 1.00; yes, 1.71 (1.12, 2.60)], and woman's education level [< or =primary school, 1.00; > or =secondary school, 1.51 (1.02, 2.22)]. Despite the fact that plant foods contributed 8 times as much vitamin A as did animal foods, serum retinol concentrations did not reflect this large difference. Home gardening and woman's education level seemed to reflect longer-term consumption of vitamin A-rich plant and animal foods, respectively.     

Infant survival is improved by oral iodine supplementation

The authors studied the relationship between brain metabolic activity and quantitative electroencephalographic power in AIDS. Basal ganglia and thalamic metabolic activity, measured with positron emission tomography, correlated positively with EEG power in the 6-10-Hz band across most head regions. Metabolic activity of anatomically defined cortical regions did not correlate with EEG power recorded over each region. These results support previously reported associations between abnormalities in subcortical metabolic activity and EEG activity. The lack of correlation between cortical metabolic activity and EEG activity suggests that previously observed abnormalities in EEG activity are primarily subcortical in origin.     

Response of Bitot's spots to a single oral 100,000- or 200,000-IU dose of vitamin A

PURPOSE: A randomized, controlled clinical trial was conducted in Indonesia to study the response of Bitot's spots to a 100,000-IU dose of vitamin A, which is known to be associated with fewer acute side effects than the currently recommended 200,000-IU dose. METHODS: A total of 114 children (ages 13 to 59 months) with Bitot's spots were given an ocular examination; serum retinol concentration was measured, and the relative dose response test carried out. After administering one 100,000- or 200,000-IU oral dose of vitamin A, ocular examinations were repeated weekly for seven weeks and then biweekly for 20 more weeks, or until lesions were healed on two consecutive examinations. RESULTS: Either dose of vitamin A was similarly effective in healing Bitot's spots. The most important factor in predicting responsiveness to treatment was baseline serum retinol concentration: children with lower pretreatment concentrations were more likely to have responsive lesions. No child had a relapse within the first three months after treatment. However, by six months, children who had received the higher dose were 82% less likely to have a relapse compared with children who had received the lower dose. CONCLUSIONS: Although either a 100,000- or 200,000-IU dose of vitamin A is similarly effective in healing Bitot's spots, a 200,000-IU dose provides longer protection. This benefit justifies the higher rates of transient mild side effects associated with the 200,000-IU dose. The current 200,000-IU dose of vitamin A recommended by the World Health Organization for prophylactic dosing should not be reduced.