beta-carotene and Infections

Vitamin A, an unsaturated 20 carbon cyclic alcohol, subserves a number of important physiological functions. However, the biochemical basis of these roles is not well understood. The main sources of retinol are liver, egg yolk and milk fat. Several carotenoids show vitamin A activity. The conversion of beta-carotene to retinol is affected by copper-containing dioxygenase and zinc-containing retinene reductase. The efficiency of conversion varies in different species. The latter is defined in units as the daily dose required to produce a weight gain of 3 g/week in young rats between the 4th and 8th week. Retinol is unstable on exposure to light or heat, particularly in the presence of heavy metal ions and water. Much recent work has focused on the absorption, metabolism and excretion of vitamin A. It is now recognized that plasma vitamin A levels do not reflect the nutritional status except in severe hypo- and hypervitaminosis A. Also, many dietary factors may influence vitamin A metabolism. These basic and applied aspects of vitamin A are reviewed.

Topics: Absorption; Animal Feed; Animal Nutritional Physiological Phenomena; Animals; Artiodactyla; beta Carotene; Biological Availability; Biological Transport; Bone Development; Carotenoids; Chemical Phenomena; Chemistry; Drug Stability; Epithelium; Female; Fish Oils; Growth; Humans; Infections; Intestinal Absorption; Intracranial Pressure; Liver; Male; Neoplasms; Nutritional Requirements; Oxidation-Reduction; Reproduction; Silage; Structure-Activity Relationship; Tretinoin; Vision, Ocular; Vitamin A

In recent years, new physiological functions of vitamin A have been identified, including its role in immune defense. The antioxidant potential of carotenoids is thought to account for their health benefits. The aim of this study was to investigate the concentration changes in the provitamin-A (alpha- and-beta-carotene, beta-cryptoxanthin) and of the non-provitamin-A carotenoids (lutein, zeaxanthin and lycopene) in children with acute infections.. Serum retinol and carotenoid concentrations were measured by HPLC in 45 children suffering from acute infections and in 29 healthy controls. In addition 15 healthy children collected food samples over 2 days. C-reactive protein (CRP) levels were measured by turbidimetry.. Serum levels of beta-carotene, alpha-carotene, beta-cryptoxanthin and retinol and non-provitamin-A carotenoid lutein and zeaxanthin concentrations were significantly lower in children with infections compared to healthy controls. There were significant negative correlations between CRP levels and serum beta-carotene and retinol concentrations. The average intake of retinol equivalents was 1.1 +/- 0.6 mg/day.. Serum retinol and provitamin-A as well as non-provitamin-A carotenoid concentrations were lower in children with acute phase infections compared to healthy controls. The inverse correlations between CRP and beta-carotene or retinol indicate either decreased synthesis or increased utilization of these antioxidants.

Topics: Adolescent; Antioxidants; beta Carotene; C-Reactive Protein; Carotenoids; Case-Control Studies; Child; Child, Preschool; Chromatography, High Pressure Liquid; Cryptoxanthins; Female; Humans; Infections; Lutein; Lycopene; Male; Vitamin A; Xanthophylls; Zeaxanthins

Topics: beta Carotene; Carotenoids; Child; Humans; Infant; Infections; Vitamin A