Bioavailability of vitamin E as function of food intake in healthy subjects: effects on plasma peroxide-scavenging activity and cholesterol-oxidation products.
Clinical trials with vitamin E have yielded contrasting results. In these trials, the amount of vitamin E given was different, and the compliance was not assessed in all studies. In addition, the modality of intake, ie, in relation to food, was not specified in any trial. Vitamin E is lipophilic, and its absorption is expected to be increased by food. We studied the bioavailability of vitamin E in relation to food intake and the effect on the lipid peroxide-scavenging activity of plasma and on 7beta-hydroxycholesterol and 7-ketocholesterol (oxysterols) as markers of oxidant stress. Twenty healthy Italian subjects were randomly assigned to take vitamin E at 300 mg/d on an empty stomach (group A) or during dinner (group B) for 15 days. Plasma vitamin E markedly increased in group B (84%) compared with group A (29%). The lipid peroxide-scavenging activity of plasma increased significantly in group B (14%, P=0.005) but did not change in group A. All subjects showed very low levels of plasma oxysterols, which were not affected by vitamin E supplementation in either group. This study shows that plasma concentration of vitamin E and plasma antioxidant activity in response to oral supplementation are markedly affected by food intake. Healthy Italian subjects show very low levels of cholesterol oxidation products; these low levels are possibly related to the Mediterranean diet. To obtain maximal absorption, vitamin E must be given at meals. These data should be taken into account in clinical trials with vitamin E.
Iuliano
L
L
Dipartimento di Medicina Interna, Istituto di Terapia Medica Sistematica, Università La Sapienza, Rome, Italy. luigi.iuliano@uniroma1.it
Micheletta
F
F
Maranghi
M
M
Frati
G
G
Diczfalusy
U
U
Violi
F
F
D000328:Adult; D001161:Arteriosclerosis / Q000188:drug therapy; D015415:Biomarkers / Q000097:blood; D004435:Eating; D005260:Female; D006801:Humans; D006888:Hydroxycholesterols / Q000097:blood*; D007653:Ketocholesterols / Q000097:blood*; D008054:Lipid Peroxides / Q000097:blood*; D008297:Male; D018384:Oxidative Stress; D014810:Vitamin E / Q000008:administration & dosage* / Q000097:blood
D015415:Biomarkers; D006888:Hydroxycholesterols; D007653:Ketocholesterols; D008054:Lipid Peroxides; D014810:Vitamin E; C011724:cholest-5-en-3 beta,7 alpha-diol; C003001:7-ketocholesterol