title: 13C natural abundance in serum retinol acts as a biomarker for increases in dietary provitamin A.
abstract: The natural isotopic composition of 13C and 12C in tissues is largely determined by the diet. Sources of provitamin A carotenoids (e.g., vegetables) typically have a lower 13C to 12C ratio (13C:12C) than preformed vitamin A sources (i.e., dairy and meat) from corn-fed animals, which are prevalent in the US. The 13C:12C of serum retinol (13C:12C-retinol) was evaluated as a biomarker for vegetable intake in a 3-mo dietary intervention designed to promote weight-loss by increased vegetable consumption or reduced calorie and fat intake. Subjects were 21-50 y of age with a BMI between 30-40 kg/m2 and were enrolled from one geographic area in the US. The high vegetable group (n=20) was encouraged to increase daily vegetable and fruit consumption to 0.95 liter vegetables and 0.24-0.35 liter fruits. The caloric reduction group (n=17) was encouraged to lower caloric intake by 500 kcal and consume<or=25% kcal from fat daily. Provided meals supplied 75-100% vegetable and fruit goals and 50-67% kcal and fat g per day. Carotenoid supplementation was discontinued by subjects during the study. Serum retinol and provitamin A carotenoid concentrations; intake of preformed vitamin A, provitamin A, and fat; and body weight, fat mass, and lean mass were analyzed for correlations to 13C:12C-retinol. 13C:12C-Retinol decreased in the vegetable group after intervention (P=0.050) and the correlation with provitamin A intake was approaching significance (P=0.079). 13C:12C-Retinol did not change in the caloric reduction group (P=0.43). 13C:12C-Retinol changes with the vitamin A source in the diet and can be used as a biomarker for increases in dietary provitamin A vegetable intake.
authors.affiliation: University of Wisconsin-Madison, Department of Nutritional Sciences, 1415 Linden Drive, Madison, WI 53706, USA.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Howe
authors.forename: Ashley R
authors.initials: AR
authors.lastname: Valentine
authors.forename: Angela K
authors.initials: AK
authors.lastname: Hull
authors.forename: Sherry A
authors.initials: SA
authors.lastname: Tanumihardjo
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D001823:Body Composition; D031204:Caloric Restriction; D002247:Carbon Isotopes; D004032:Diet; D005260:Female; D005638:Fruit; D006801:Humans; D008297:Male; D008875:Middle Aged; D012015:Reference Standards; D014675:Vegetables; D014801:Vitamin A / Q000097:blood* / Q000378:metabolism*; D019207:beta Carotene / Q000097:blood*
chemical_list: D015415:Biomarkers; D002247:Carbon Isotopes; D019207:beta Carotene; D014801:Vitamin A