title: Intra- and interindividual variation in measurements of beta-carotene, retinol, and tocopherols in diet and plasma.
abstract: Twenty-four men were studied for 4 wk to estimate intra- and interindividual variation of retinol, beta-carotene, and tocopherols in diet and plasma. Ratios of intra- to interindividual variances ranged from 0.62 for beta-carotene in plasma to 6.02 for vitamin E in diet. Results indicate that 3-9 independent measurements may be required to distinguish reliably even large differences (approximately 1 SD) in these micronutrients; 28-86 independent measurements may be needed for small differences (approximately 0.25 SD). If uncontrolled, large ratios of intra- to interindividual variance can constitute an important source of error in studies of micronutrients.
mesh_terms: D000328:Adult; D002338:Carotenoids / Q000008:administration & dosage / Q000097:blood*; D004032:Diet; D006801:Humans; D008297:Male; D011939:Mental Recall; D008875:Middle Aged; D013223:Statistics as Topic; D014280:Triglycerides / Q000097:blood; D014801:Vitamin A / Q000008:administration & dosage / Q000097:blood*; D014810:Vitamin E / Q000008:administration & dosage / Q000097:blood*; D019207:beta Carotene
chemical_list: D014280:Triglycerides; D019207:beta Carotene; D014801:Vitamin A; D014810:Vitamin E; D002338:Carotenoids