title: Effects of beta-carotene supplementation on free radical mechanism in healthy adult subjects.
abstract: OBJECTIVE
  The objective of this study was to examine whether increasing doses of beta-carotene supplements have effects on biological markers of lipid peroxidation in healthy volunteers.
  
  
  METHODS
  Forty-two healthy subjects were supplemented with 5 mg, 10 mg, 20 mg or 40 mg beta-carotene/day, respectively for five weeks. Plasma beta-carotene and tocopherol levels, malondialdehyde-thiobarbituric reactive substances (MDA-TBARS), and conjugated dienes were determined using high-performance liquid chromatography (HPLC). Concentrations of ascorbic acid, uric acid, and the total antioxidative capacity (TAC) in plasma were measured photometrically.
  
  
  RESULTS
  Plasma beta-carotene levels increased significantly according to the intervention dose (p < 0.001), and concentrations of tocopherol equivalents and ascorbic acid were within the physiological range except in the 5 mg intervention group where a significant decrease of vitamin C was assessed (p < 0.05). Uric acid in plasma decreased significantly in all groups (p < 0.05) up to the end of investigation, but was within the normal range. Trolox equivalent antioxidative capacity (TEAC) decreased significantly (p < 0.001) in all groups during supplementation. MDA-TBARS remained unchanged after five weeks except for the 40 mg beta-carotene substitution group, where a significant decrease was observed (p < 0.05).
  
  
  CONCLUSIONS
  Beta-carotene supplementation of healthy subjects significantly increased plasma beta-carotene status without inducing adverse biological effects. Beta-carotene did not especially protect against oxidative stress, except for the 40 mg group. These data suggest that additional effects of beta-carotene supplementation on well-nourished, healthy subjects are limited.
authors.affiliation: Institute of Nutritional Sciences, University of Vienna, Vienna, Austria.
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Elmadfa
authors.forename: Petra
authors.initials: P
authors.lastname: Rust
authors.forename: Dorota
authors.initials: D
authors.lastname: Majchrzak
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Wagner
authors.forename: Dieter
authors.initials: D
authors.lastname: Genser
authors.forename: Regina
authors.initials: R
authors.lastname: Lettner
authors.forename: Marika
authors.initials: M
authors.lastname: Pinter
mesh_terms: D000328:Adult; D000975:Antioxidants / Q000032:analysis; D001205:Ascorbic Acid / Q000097:blood; D002851:Chromatography, High Pressure Liquid; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D005260:Female; D005609:Free Radicals; D006801:Humans; D015227:Lipid Peroxidation / Q000187:drug effects*; D008297:Male; D008315:Malondialdehyde / Q000097:blood; D018384:Oxidative Stress / Q000187:drug effects; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis; D024505:Tocopherols / Q000097:blood; D014527:Uric Acid / Q000097:blood; D019207:beta Carotene / Q000008:administration & dosage* / Q000097:blood
chemical_list: D000975:Antioxidants; D005609:Free Radicals; D017392:Thiobarbituric Acid Reactive Substances; D019207:beta Carotene; D014527:Uric Acid; D008315:Malondialdehyde; D001205:Ascorbic Acid; D024505:Tocopherols