Vitamin C overview and essential roles

Summary

Vitamin C (ascorbic acid) is a water-soluble essential nutrient found in citrus fruits, berries, and vegetables. It exists in biological systems mainly as ascorbic acid/ascorbate and plays critical roles in tissue repair, collagen formation, and the enzymatic production of certain neurotransmitters. It also supports immune function and acts as an antioxidant, helping protect cells from oxidative damage. Humans and some other animals (e.g., higher primates, many bats, guinea pigs, and some fish/bird species) cannot synthesize vitamin C effectively, so it must be obtained from the diet. A key clinical importance of vitamin C is its prevention and treatment of scurvy, a disease caused by vitamin C deficiency. Without adequate vitamin C, collagen becomes unstable and multiple enzymes fail to function properly, leading to symptoms such as fatigue, bruising, bleeding under the skin, gum bleeding, and in severe cases, open wounds, tooth loss, and death. Vitamin C status can be assessed using plasma measurements, and recommended intakes vary by country; large supplemental doses are generally well tolerated but may cause gastrointestinal discomfort and other side effects, so guidelines often discourage excessive intake.

Key Points

• 1

  Vitamin C is an essential, water-soluble nutrient required for collagen formation, tissue repair, immune function, and antioxidant activity.

• 2

  Humans largely rely on dietary sources because many cannot synthesize vitamin C; deficiency leads to scurvy with progressive, potentially severe symptoms.

• 3

  Vitamin C status is commonly evaluated via plasma levels, and intake recommendations and upper limits differ by national health authorities.