NARRATIVE REVIEW: BIOAVAILABILITAS VITAMIN A IN VIVO, PERAN FORMULASI PANGAN, METABOLISME, DAN PENYIMPANAN HEPATIK : Narrative Review: Bioavailability Of Vitamin A In Vivo, The Role Of Food Formulation, Metabolism, And Hepatic Storage

Vitamin A is an essential micronutrient that plays a crucial role in vision, immune system function, and cell differentiation. However, its bioavailability is relatively low and is significantly influenced by food formulation factors, the presence of lipids, and an individual’s physiological condition. This review aims to comprehensively synthesize and evaluate in vivo evidence regarding vitamin A bioavailability, covering intestinal absorption, the conversion of β-carotene to retinol, and hepatic storage as key indicators of vitamin A status. The method used was a literature review of ten in vivo studies from 2017–2025 obtained from the PubMed, Scopus, and Google Scholar databases. The results of the review indicate that lipid-based delivery systems, such as nanoemulsions and microencapsulation, can enhance bioavailability by improving the solubilization, micellization, and stability of vitamin A. The presence of lipids has been shown to be the primary limiting factor in absorption, while the food matrix and competition among carotenoids modulate absorption efficiency. Additionally, the conversion of β-carotene to retinol is influenced by enzymatic regulation, baseline vitamin A status, and gender. Another key finding indicates that plasma retinol levels do not always reflect vitamin A status because they are homeostatically regulated, whereas the majority of vitamin A is stored in the liver as retinyl esters, making it a more representative indicator of bioavailability. Thus, the bioavailability of vitamin A is multidimensional and must be evaluated through an integrative approach that encompasses formulation, physiological, and hepatic storage aspects.