Vitamin A status in young adults: serum and diet markers and their correlation with visual function.

Abstract

Introduction: Vitamin A is essential in visual process and its nutritional status can be evaluated by dietary intake or blood concentrations. In blood, a-carotene, b-carotene and b-cryptoxanthin represent the main provitamin-A-carotenoids. Data in foods can be obtained from specific food composition tables/database. Objectives: 1)Assessment of provitamin-A carotenoids (bcarotene, a-carotene, b-cryptoxanthin) and retinol in serum and diet of young adults, and of visual function. 2)Evaluate correlations among serum and diet markers and visual function. Method/Design: Subjects (n=50; 23men), 25,4±3,2 years-old. Inclusion criteria: normal cholesterolaemia, mixed diet. Exclusion criteria: obesity, dietary supplements, myopia surgery. Study approved by CREC. Methods: HPLC validated method for serum carotenoids. 3-day-records-questionnaires assessed using a food composition database. Contrast Sensitivity (CS) with and without glare (6 stimulus sizes -6.3 to 0.7 degrees) at three spatial frequencies (Takagi, CGT- 1000). Statistical analysis: Kolmogorov-Smirnoff, one-way ANOVA, Spearman\¿s correlations. Results: Vitamin A dietary markers concentration (median, ¿g/day): b-carotene 1196, a- carotene 166, b-cryptoxanthin 36, retinol 273 and vitamin A (retinol-activity-equivalents) 404. Median concentrations in serum (¿g/dl): b-carotene 13, a-carotene 3; b-cryptoxanthin 9. No differences were found in any between sexes but serum retinol (63±10 and 51±15ug/dl, men and women, respectively). CS showed differences, when tested with and without glare, at high and medium frequency (25 % and 83% respectively; lower values obtained with glare). Serum provitamin-A-carotenoids concentration showed correlation with their intake (r=0.361, p=0.000). Individually: r=0.494 for b-cryptoxanthin, r= 0.349 for a-carotene and no significative for b-carotene. Serum retinol correlates with provitamin-A carotenoid intake (r=0.197, p=0.045) and with CS at medium frequency (r=0.212, p=0.034). Conclusions: Vitamin A nutritional status assessed by dietary or biochemical markers lead to different results, adequate status considering retinol in serum but inadequate regarding intake. Contrast sensitivity correlates with serum retinol but not with any of the other markers assessed. Acknowledgments: Instituto de Salud Carlos III (AES, PS09/00681). ML.García-González for HPLC assistance. Key Words: retinol, b-carotene, a-carotene, b-cryptoxanthin, diet, serum, contrast sensitivity.