Study on Vitamin A Requirement of Adult Chinese by Isotope Dilution Technique and β‐carotene Intervention Trial

The goal of this study is to determine dietary vitamin A requirement for keeping constant vitamin A pool in body in Chinese population. Total 102 healthy adult volunteers (50 males and 52 females, aged 49.0ys) were recruited for this vitamin A (VA) requirement study. Each volunteer was first given a dose of 1mg 2 H 4 ‐retinyl acetate after a fasting blood sampling for a 21d metabolic experiment to detect liver vitamin A storage (LAS) before β‐carotene (β‐C) supplement intervention. At the 21 st day after taking the dose, a fasting blood sample was collected once again from each subject. The volunteers were then randomly divided into 4 groups and were given all‐trans β‐C supplementation with different doses of 0mg/d, 1.8mg/d, 3.6mg/d, 5.4mg/d in capsules for 4 months. After the end of β‐C intervention period, another 21d experiment was repeated with doses of 1 mg 2 H 8 ‐retinyl acetate for detection of LAS again. During the metabolic experiment and intervention periods, the volunteers kept low retinol and pro‐VA diet. Serum retinol and carotenoid concentrations were analyzed with HPLC. The serum retinol enrichment was detected with GC‐MS. Then total LAS were calculated by Furr‐Olson Formula. Dietary VA intake for maintaining LAS unchanged was estimated by dose‐effect relationship of dietary VA intake and LAS change value before and after intervention. Total 99 subjects finished all experiments. The average VA intake from daily diets was about 393.34μgRAE/d. And 120.2μgRAE/d of it was contributed by dietary retinol, and other came from dietary carotenoids. There was no difference of serum retinol concentration as well as β‐C concentration between four groups before intervention (P>0.05). After intervention, there was no significant increase of serum retinol concentration. Except from control group, serum β‐C increased obviously after intervention in three supplemented groups especially the group with highest supplement dose (P<0.05). The LAS before intervention averaged 660.9μmol (189.3mg) from all subjects. The LAS increased in two higher supplement dose groups, but unchanged or decreased slightly in relative lower dose and control groups. The average change of LAS for all subjects was 138.6μmol. There was significant correlation between LAS change and dietary VA equivalent (RE) or dietary vitamin A activity equivalent (RAE) (p<0.001). When the equivalents to VA of pure β‐C in capsule were assumed as 1:2, 1:6 or 1:12, five pairs of linear regression equations were obtained with valid data from 99 subjects for predicting LAS change (y, μmol) with total dietary RE or RAE (x, μgRE or μgRAE). Assuming 1/2 as the equivalent ratio to VA of supplemented β‐C, the predicted values of dietary VA intakes for maintaining total LAS unchanged was about 826.7μgRAE for male and 1118.2μgRAE for female; when 1/6 as the ratio, the predicted dietary VA should be 507.31μgRAE (male) and 580.32μgRAE (female); and the dietary VA should be 420.9μg (male) and 432.0μgRAE (female) when 1/6 be used as the ratio. From β‐C view, the dietary intake for keeping the LAS unchanged should be 4200μg (male) and 4050μg(female) all‐trans β‐C (including dietary and supplemental source) in the subjects each of whom has about daily 130μg (male) and 110μg (female) dietary retinol and 360μg (male) and 2850μg (female) dietary β‐carotene. Support or Funding Information This study was supported by a grant from National Natural Science Foundation of China (81172654) and financed partly by a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD); The bata‐carotene supplement capsules were sponsored and provided by DSM Nutritional Products Ltd, Switzerland.