Vitamin C (Ascorbic Acid)

What Is Vitamin C (Ascorbic Acid)?

Vitamin C, chemically known as ascorbic acid, is a water-soluble vitamin and potent antioxidant. Unlike most mammals, humans lack the enzyme L-gulonolactone oxidase and cannot synthesize vitamin C endogenously; it must therefore be obtained entirely from the diet. Vitamin C was identified as the factor preventing scurvy, a disease that decimated sailors on long sea voyages before the eighteenth century.

The RDA for adults is 90 mg/day for men and 75 mg/day for women. Smokers require an additional 35 mg/day due to increased oxidative stress. The UL is 2,000 mg/day.

Key Functions

• Collagen synthesis: Ascorbic acid is an essential cofactor for prolyl and lysyl hydroxylases, enzymes that hydroxylate proline and lysine residues in collagen precursors. Without vitamin C, collagen triple helices are unstable, impairing wound healing, blood vessel integrity, and bone matrix — the hallmarks of scurvy.
• Antioxidant: Vitamin C scavenges reactive oxygen species (ROS) and regenerates vitamin E from its oxidized form, protecting cell membranes from lipid peroxidation.
• Iron absorption: Converts dietary non-heme iron (Fe3+) to the more absorbable ferrous form (Fe2+), and chelates iron in the gut lumen, enhancing absorption up to threefold.
• Immune support: Supports neutrophil function, lymphocyte proliferation, and antibody production.
• Carnitine and neurotransmitter synthesis: Required for synthesis of carnitine (fatty acid transport into mitochondria) and certain neurotransmitters including norepinephrine.

Food Sources

Exceptionally rich sources include guava (228 mg/100 g), bell peppers (red: 128 mg/100 g), kiwi, citrus fruits (oranges approximately 53 mg/100 g), strawberries, papaya, and broccoli. Vitamin C is highly heat-labile and water-soluble; steaming or microwaving preserves more than boiling.