Ingredient review
Vitamin C
Description
What is it?
Vitamin C (ascorbic acid) is an essential, water-soluble vitamin. It is well-known for its antioxidative properties and ability to reduce free radicals by donating electrons through reduction reactions. (20) The discovery of vitamin C has been attributed to the treatment of scurvy in sailors and the potato famine in Ireland. (4)
Not to be confused with: L-threonate
Download ingredient reviewMain uses
Cardiovascular disorders
Chronic pain & inflammation
Immune function
Metabolic disorders
Formulations
Form
Bioavailability
Ascorbic acid - liposomal
Relative bioavailability of liposomal-encapsulated ascorbic acid was increased by ~74% higher than unformulated ascorbic acid (7)
Ascorbic acid - unformulated
200 mg doses produces a plateau in plasma concentration, with full plasma saturation at 1000 mg (18)
Ascorbic acid - sustained-release
Conflicting evidence on bioavailability:
Within 4-12 hours, single admin of fast release formulation increased relative plasma ascorbate by 94% (non-stat. signi.) than slow release. After 2-months, slow-release was 22% higher (non-stat. signi.) (24)
Single admin of slow-release formulations increased relative bioavailability of plasma ascorbate by 23-51% (stat. signi.) than fast-release tablets or solution (2)
Ascorbyl palmitate
Increased bioavailability compared with ascorbic acid in horses (28)
Calcium ascorbate
Magnesium ascorbate
No information on bioavailability currently available
Potassium ascorbate
No information on bioavailability currently available
Sodium ascorbate
No information on bioavailability currently available
Vitamin C with bioflavonoids
No difference in bioavailability with AA or Ester C (14)
Dosing & administration
Blood pressure
Dosing & administration
0.5 g per day
Outcomes
systolic & diastolic blood pressure (15)
Class of evidence
a
Common cold
Complex regional pain syndrome
Gout
Osteoarthritis
Post operative atrial fibrillation
Dosing & administration
2.0 g pre-op + 1.0-2.0 g post-op
Outcomes
risk of AF (12)
Class of evidence
a
Adverse effects
Vitamin C is considered to be safe and tolerable. Exceeding the Tolerable Upper Intake Level (UL) of 2000 mg per day for adults can lead to gastrointestinal disturbances and osmotic diarrhea. The daily UL for children aged one to three is 400 mg, aged four to eight is 650 mg, and aged nine to 13 is 1800 mg. (9)
Pharmacokinetics
Absorption
- Vitamin C predominantly exists in its reduced form, ascorbate, though it can be found in its oxidized form as dehydroascorbic acid (DHA). (21)
- Ascorbate and DHA are efficiently interconvertible, but may be absorbed via different mechanisms. (21)
- Ascorbate is absorbed via active transport in the small intestine through sodium-dependent vitamin C transporter 1 (SVCT1). (19)(21)(27)
- DHA has a similar structure to glucose and is absorbed into the intestinal epithelium by glucose transporters GLUT1 and GLUT3, and into the blood by GLUT1 and GLUT2. (21)(26)
Distribution
- Vitamin C can be primarily found circulating in plasma and erythrocytes (50-70µM), but can be found in the adrenals (4-10 µM), brain (2-10 µM), liver (~1 µM), lung (~1 µM), kidney (0.3-0.5 µM), heart (0.2-0.4 µM), and muscle (0.2-0.4 µM). (21)
Metabolism
- Ascorbate is an electron donor, acting as an antioxidant. Ascorbate is oxidized to the stable ascorbyl free radical.
- Intracellularly, DHA is efficiently reduced to ascorbate, recycling ascorbate pools. (21)