Vitamin c digestion
Pro Research Analysisby 
Searched over 200M research papers
Vitamin C Digestion: Stability, Bioaccessibility, and Transport
Stability of Vitamin C During Gastrointestinal Digestion
Gastric Stability of Vitamin C
Vitamin C, also known as ascorbic acid, demonstrates considerable stability under gastric conditions. Studies on various fruit juices, such as blended fruit juice (BFJ) containing orange, pineapple, and kiwi, have shown that vitamin C remains largely stable during the gastric phase of digestion, with a recovery rate exceeding 75% . Similarly, research on broccoli inflorescences indicates that vitamin C experiences minimal degradation (around 7%) during gastric digestion .
Intestinal Degradation of Vitamin C
However, the stability of vitamin C significantly decreases during the intestinal phase. In the case of BFJ, the bioaccessibility of vitamin C drops to about 15% after small intestinal digestion . Pomegranate juice studies reveal an even more drastic reduction, with over 95% of vitamin C being degraded during intestinal digestion . Broccoli inflorescences also show a substantial loss of vitamin C, with a 91% decrease observed under intestinal conditions .
Bioaccessibility of Vitamin C
Hydrophilic vs. Lipophilic Constituents
The bioaccessibility of vitamin C, a hydrophilic compound, is generally higher compared to lipophilic constituents. In BFJ, vitamin C shows a bioaccessibility of 15%, which is higher than that of carotenes and xanthophylls, which are around 7.6% and 17.4%, respectively . This trend is consistent across different food matrices, indicating that the hydrophilic nature of vitamin C facilitates its absorption.
Impact of Supplement Composition
The composition of vitamin C-based supplements also affects its bioaccessibility and the oxidative stability of other nutrients. Supplements containing pure l-ascorbic acid can enhance lipid oxidation during digestion, leading to the formation of various oxidation compounds and the degradation of gamma-tocopherol . Conversely, supplements that include mixtures of ascorbic acid with citric acid and carotenes, or ascorbyl palmitate, can protect against lipid oxidation and maintain higher bioaccessibility .
Mechanisms of Vitamin C Transport
Absorption and Cellular Uptake
Vitamin C is absorbed in the intestine and renal tubules through specific transport mechanisms. Ascorbic acid and its oxidized form, dehydroascorbic acid (DHAA), are taken up by enterocytes and renal epithelial cells. The transport of vitamin C across the plasma membrane involves facilitated diffusion of DHAA through glucose-sensitive and -insensitive transporters, and secondary active transport of ascorbate via sodium-dependent vitamin C transporters (SVCT1 and SVCT2) . These transport pathways are crucial for concentrating vitamin C intracellularly, enhancing its role as an enzyme cofactor and antioxidant.
Regulation of Transport Pathways
The transport mechanisms for vitamin C are regulated under physiological conditions and can be altered by factors such as aging and disease. The genes Slc23a1 and Slc23a2 encode the SVCT1 and SVCT2 proteins, respectively, which are essential for the active transport of ascorbate . Understanding these regulatory mechanisms is vital for optimizing vitamin C absorption and utilization in the body.
Conclusion
Vitamin C exhibits significant stability during the gastric phase of digestion but undergoes substantial degradation in the intestinal phase. Its bioaccessibility is higher compared to lipophilic compounds, and the composition of vitamin C supplements can influence its oxidative stability and bioaccessibility. The absorption and transport of vitamin C are mediated by specific transporters, which are regulated under various physiological conditions. These insights are crucial for developing dietary strategies to enhance vitamin C intake and utilization.
Sources and full results
Most relevant research papers on this topic