Vitamin C is a nutrient and antioxidant that supports overall health. It contributes to various bodily functions, including immune support and collagen production. Despite its many benefits, vitamin C is unstable and degrades over time.
Understanding Vitamin C Oxidation
Vitamin C is susceptible to a chemical process called oxidation. Oxidation refers to the loss of electrons from a molecule, which alters its chemical structure and properties. When ascorbic acid undergoes oxidation, it transforms into dehydroascorbic acid (DHA).
While dehydroascorbic acid can still offer some biological activity, this transformation reduces or eliminates vitamin C’s antioxidant capabilities. Oxidation leads to a loss of the vitamin’s potency and effectiveness. If dehydroascorbic acid reacts further, it can undergo irreversible reactions, leading to a complete loss of vitamin C content.
Key Factors Accelerating Oxidation
Several factors can accelerate the oxidation of vitamin C. Light, particularly UV radiation, provides the energy needed to initiate and speed up degradation. Heat also increases the rate of oxidation, making vitamin C more unstable at higher temperatures.
Exposure to air, meaning oxygen, is a primary factor, as oxygen directly participates in the chemical reaction that breaks down ascorbic acid. The presence of certain metal ions, such as copper and iron, can act as catalysts, speeding up vitamin C degradation even at low concentrations.
Strategies to Prevent Oxidation
Minimizing vitamin C oxidation involves careful handling and storage. For supplements, storing them in cool, dark places away from direct sunlight and heat preserves integrity. Airtight containers are also beneficial, as they limit exposure to oxygen.
For skincare products, choosing formulations packaged in opaque or dark glass containers or airless pump bottles shields the product from light and air. Refrigeration can further extend the shelf life of vitamin C serums in a cool, dark environment. For food sources rich in vitamin C, such as fruits and vegetables, consuming them fresh or storing them properly in a refrigerator can slow vitamin C loss.
Recognizing Oxidized Vitamin C
Identifying oxidized vitamin C is straightforward, as it presents with changes in appearance and odor. A primary indicator is a color change; fresh products are clear or pale yellow, while oxidized products turn deeper yellow, orange, or brown. An altered smell also signals oxidation; fresh products have a neutral scent, but oxidized ones may develop a metallic or “off” odor.
For liquid products, changes in texture, such as thickening, can also occur. If any of these signs are observed, it indicates that the vitamin C has degraded and may no longer provide its intended benefits.