Vitamin C (Ascorbic Acid)

Ascorbic acid is essential for the enzymatic amidation of neuropeptides, production of adrenal cortical steroid hormones, promotion of the conversion of tropocollagen to collagen, and metabolism of tyrosine and folate. It also plays a role in lipid and vitamin metabolism and is a powerful reducing agent or antioxidant. Specific actions include activation of detoxifying enzymes in the liver, antioxidation, interception and destruction of free radicals, preservation and restoration of the antioxidant potential of vitamin E, and blockage of the formation of carcinogenic nitrosamines. Vitamin C promotes collagen synthesis, maintains capillary strength, facilitates release of iron from ferritin to form hemoglobin, and functions in the stress response. In addition, vitamin C appears to function in a variety of other metabolic processes in which its role has not been well characterized.

Normal range: 0.4 " “2.0 mg/dL.

Use

Investigate suspected metabolic or malabsorptive disorders

Investigate suspected scurvy

Interpretation

Decreased In

Alcoholism

Anemia

Cancer

Hemodialysis

Hyperthyroidism

Malabsorption

Pregnancy

Rheumatoid disease

Scurvy

Limitations

Drugs and substances that may decrease vitamin C levels include acetylsalicylic acid, aminopyrine, barbiturates, estrogens, heavy metals, oral contraceptives, nitrosamines, and paraldehyde.

Chronic tobacco smoking decreases vitamin C levels.

Testing of nonfasting specimens or the use of vitamin supplementation can result in elevated plasma vitamin concentrations. Reference values were established in patients who were fasting.

After consuming vitamin C, plasma values rapidly rise within 1 " “2 hours and reach peak concentration within 3 " “6 hours after ingestion.