Vitamin C functions primarily to form collagen, the primary protein used to
make connective tissue and form scar tissue, and is needed to form bone, and
cartilage. Vitamin C is also an antioxidant which protects all cells from
oxidative damage. It also protects other vitamins such as vitamin E and A from
oxidation as well. Research has shown that vitamin C protects the body against
heart disease and many types of cancer. It is essential to proper wound healing,
and has shown benefit for use in treating exercise-induced asthma. Most
importantly, it is now known that vitamin C is critical to proper immune system
function. Infection and inflammation rapidly deplete vitamin C from the body.
Constant replacement is needed in order to maximize immune function and overcome
Probably the biggest controversy surrounding vitamin C in the past few
decades is whether or not it prevents colds. Research has shown that vitamin C
does reduce the formation of histamine, which may help reduce cold symptoms.
Clinical studies have shown that although vitamin C can reduce the length and
severity of cold symptoms, it has not yet been proven to prevent colds. However,
maintaining a strong and healthy immune system which increases resistance to all
types of infection and disease is a good reason for consuming adequate amounts
of vitamin C. The latest research on vitamin C shows that it is protective
against sunburn and reduces the development of nitrate tolerance during
nitroglycerin therapy in congestive heart failure patients.
Vitamin C is present in many fruits and vegetables. The following foods are
excellent sources of vitamin C: orange juice, green peppers, watermelon, papaya,
grapefruit juice, grapefruit, cantaloupe, strawberries, mango, broccoli, tomato
juice, brussels sprouts, cauliflower, and cabbage. Vitamin C is also found in
raw and cooked leafy greens, (turnip greens, spinach), canned or fresh tomatoes,
potatoes, winter squash, raspberries, and pineapple. Vitamin C is sensitive to
light, air, and heat. Eating vegetables raw, or minimally cooked, increases
their vitamin C content.
Vitamin C is ascorbic acid. It becomes dehydroascorbic acid when it is
oxidized by the body. Ascorbic acid is the form that is used for supplements and
as a food additive to protect against oxidative spoilage.
You can purchase either natural or synthetic ascorbic acid in a wide variety
of supplement forms. Tablets, capsules, and chewable tablets are probably the
most popular, but vitamin C also comes in powdered crystalline, effervescent
tablet and liquid form. You can purchase dosages from 25 mg to 1,000 mg per
tablet; the most common are 100 mg, 250 mg, 500 mg, and 1,000 mg. "Buffered" C
is available for those who find regular ascorbic acid is too harsh for their
stomachs. "Ester-C" is a form of vitamin C composed of esters, which is promoted
to be better absorbed by the body. Laboratory testing has challenged this claim,
showing that absorption did not differ significantly from regular vitamin C.
- Boosts immune functions
- Protects against cancer
- Necessary for wound healing
- Helps prevent cataract development
- Increases HDL (good) cholesterol
- Decreases risk of cardiovascular disease
- Reduces blood pressure
- Decreases histamine levels (useful in treating allergies)
- Reduces capillary fragility
- Counteracts asthma (reduces airway spasms)
- Helps overcome male infertility
- Used in treatment of cervical dysplasia
- Helps protect diabetics against long-term complications by lowering
sorbitol levels and reducing glycosylation of proteins
- Protects against sunburn and its effects
- Increases integrity of connective tissue, assisting treatment of
bleeding gums, bruising, and arthritis
- Is anti-inflammatory
- Protects fat-soluble antioxidants (e.g., vitamin E) from
|Dosage Ranges and Duration of
The range of safe vitamin C intake appears to be very broad, and research has
proved that even very high daily doses over 10 g (10,000 mg) for extended
periods of time are usually well tolerated. Although the minimum daily
requirement is 60 mg/day, physical stresses such as exertion, illness,
infection, surgery, wound healing, exposure to toxic chemicals and metals, high
or low temperatures, smoking, and chronic use of medication all increase the
need for vitamin C. The amount needed varies with the severity of the stress,
but may be as high as 1,000 mg/day or even higher. While consuming 60 mg/day of
vitamin C may be sufficient to prevent deficiency symptoms, at least 100 to 250
mg is needed to saturate the tissues. And, since vitamin C is water-soluble and
not stored in the body, the tissue supply requires constant replacement. Eating
foods rich in vitamin C and/or dividing a supplement dose to be taken bid or tid
is optimal. General recommendations for vitamin C intake is 250 to 500 mg/day
for the average healthy adult. Some nutritionists recommend 500 to 1,000 mg tid
(with each meal) for recovery after illness, surgery, or severe injury.
Vitamin C is considered nontoxic; excesses are excreted by the body. High
doses of vitamin C can cause diarrhea, and nutritionists state that this side
effect is useful in assessing an individual's tolerance and optimal daily
allowance for proper tissue saturation. Diarrhea, gas, or other intestinal
disturbances are harmless and reversible with lower dosing. Although the
literature is full of speculated warnings, no harmful effects even from
long-term "megadosing" have been observed.
Individuals with a history of kidney problems of any kind may not be
candidates for vitamin C supplements due to increased urinary oxalate formation
in oxalate kidney stone formers. Infants born to mothers taking 6 g or more of
vitamin C may develop rebound scurvy after birth, due to the sudden drop in
Oral administration of vitamin C (3 gm po) 90 minutes after acetaminophen
dosing has been shown to cause a rapid and pronounced decrease in the excretion
rate of acetaminophen sulfate (Houston and Levy
In a double-blind, randomized, crossover study designed to evaluate the
effects of aspirin on gastroduodenal injury, 14 healthy volunteers received
aspirin (900 mg bid) and either allopurinol (100 mg bid), sulphasalazine (1 g
bid), vitamin C (1 g bid), or placebo (McAlindon et al. 1996). Vitamin C reduced
aspirin-induced duodenal injury. Renal clearance of aspirin and other acidic
medications may also be reduced by high doses of vitamin C (500 mg/day or more),
especially in older patients (Schumann
In dogs, the combination of furosemide (20 mg IV or 40 mg po) and ascorbic
acid (150 mg or 500 mg po) increased both urinary output and excretion of
unchanged furosemide (Lee and Chiou 1998). Similar results were observed in rats
treated with both furosemide (6 mg po) and ascorbic acid (up to 100 mg po).
Administration of vitamin C during long-term nonintermittent administration
of glycerolnitrate eliminated vascular tolerance in healthy subjects (Bassenge
et al. 1998). In a double-blind, placebo-controlled study with 24 healthy
volunteers and 24 patients with ischemic heart disease, coadministration of
vitamin C (2 g tid) and nitroglycerin prevented nitrate tolerance (Watanabe et
al. 1998a). Concomitant administration of intravenous vitamin C and
nitroglycerin also prevented nitrate tolerance in patients with congestive heart
failure (Watanabe et al. 1998b).
Anti-Inflammatory Drugs (NSAIDs)
Vitamin C (1 g bid) protects against aspirin-induced duodenal injury; it may
also protect against gastroduodenal injury induced by other NSAIDs such as
ibuprofen (McAlindon et al.
Ascorbic acid (1 g) can interfere with oral contraceptive metabolism, leading
to higher blood levels of estradiol (Stockley 1999). However, daily use of
ascorbic acid and a combination oral contraceptive (30 µg ethinyl estradiol and
150 µg levonorgestrel) in 37 women for two consecutive cycles did not affect
Cmax and AUC values for ethinyl estradiol (Zamah et al. 1993). A similar study
also found that vitamin C did not affect Cmax and AUC values for levonorgestrel
(Kuhnz et al. 1995). In addition, vitamin C exhibited antioxidant effects when
supplied with 17beta-estradiol close to physiological levels (Huang et al.
1999). It protected LDL from oxidation in vitro; 17beta-estradiol monotherapy
had no antioxidant
Administration of propranolol (80 mg po) to five healthy volunteers
pretreated with ascorbic acid (2 g) affected the absorption and metabolism of
the drug (Gonzalez et al. 1995). This combination decreased maximum plasma
concentrations and urinary excretion of the drug, and increased the time to
In one study, the bioavailability of tetracycline hydrochloride was increased
by concomitant administration of vitamin C (100 mg/day) in healthy subjects
(Omray 1981). More research is needed to confirm these
There are case reports of decreased prothrombin in patients taking vitamin C
and warfarin (Harris 1995; Smith 1972). In one case, the patient was taking high
doses of vitamin C (16 g/day) (Smith 1972). In follow-up studies, no association
was found between vitamin C (1 g/day) and warfarin in humans (Harris 1995).
Patients taking warfarin should not exceed the recommended dietary allowance for
vitamin C (60 mg/day for adults).
Bassenge E, Fink N, Skatchkov M, Fink B. Dietary supplement with vitamin C
prevents nitrate tolerance. J Clin Invest. 1998;102(1):67-71.
Cohen H, Neuman I, Nahum H. Blocking effect of vitamin C in exercise-induced
asthma. Arch Pediatr Adolesc Med. 1997;151:367-370.
Eades MD. The Doctor's Complete Guide to Vitamins and Minerals. New
York, NY: Dell Publishing; 1994.
Eberlein-Konig B, Placzek M, Przybilla B. Protective effect against sunburn
of combined systemic ascorbic acid (vit.C) and D-alpha-tocopherol (vit.E). J
Am Acad Dermatol. 1998;38:45-48.
Galley HF, Thornton J, et al. Combination oral antioxidant supplementation
reduces blood pressure. Clin Sci. 1997;92:361-365.
Gonzalez J, Valdivieso A, Calvo R, Rodriguez-Sasiain J, et al. Influence of
vitamin C on the absorption and first pass metabolism of propranolol. Eur J
Clin Pharmacol. 1995;48:295-297.
Harris JE. Interaction of dietary factors with oral anticoagulants: review
and applications. J Am Diet Assoc. 1995;95(5):580-584.
Hendler SS. The Doctors' Vitamin and Mineral Encyclopedia. New York,
NY: Fireside Press, 1991.
Hines Burnham, et al, eds. Drug Facts and Comparisons. St. Louis,
MO:Facts and Comparisons; 2000:452.
Houston JB, Levy G. Drug Biotransformation interactions in man VI:
acetaminophen and ascorbic acid. J Pharm Sci. 1976;65(8):1218-1221.
Huang M, Li J, Teoh H, Man RY. Low concentrations of 17beta-estradiol reduce
oxidative modification of low-density lipoproteins in the presence of vitamin C
and vitamin E. Free Radic Biol Med. 1999; 27(3-4):438-441.
Kuhnz W, Olouton T, Humpel M, Back D, Zamah N. Influence of high doses of
vitamin on the bioavailability and the serum protein binding of levonorgestrel
in women using a combination oral contraceptive. Contraception.
Lee M, Chiou W. Mechanism of ascorbic acid enhancement of the bioavailability
and diuretic effect of furosemide. Drug Metab Dispos.
Lieberman S, Bruning N. The Real Vitamin & Mineral Book. 2nd ed.
New York, NY: Avery Publishing Group; 1997.
Mahan K, Arlin M, eds. Krause's Food, Nutrition and Diet Therapy. 8th
ed. Philadelphia, Pa: WB Saunders Co; 1992.
McAlindon M, Muller A, Filipowicz B, Hawkey C. Effect of allopurinol,
sulphasalazine, and vitamin C on aspirin induced gastroduodenal injury in human
volunteers. Gut. 1996;38:518-524.
Mosca L, et al. Antioxidant nutrient supplementation reduces the
susceptibility of low density lipoprotein to oxidation in patients with coronary
artery disease. J Am Coll Cardiol. 1997;30:392-399.
Murray MT. Encyclopedia of Nutritional Supplements. Rocklin, Calif:
Prima Publishing; 1996.
Omray A. Evaluation of pharmacokinetic parameters of tetracylcine
hydrochloride upon oral administration with vitamin C and vitamin B complex.
Hindustan Antibiot Bull. 1981;23(VI):33-37.
Schumann K. Interactions between drugs and vitamins at advanced age. Int J
Vitam Nutr Res. 1999;69:3173-178.
Smith EC. Interaction of ascorbic acid and warfarin [letter]. JAMA.
Stockley IH. Drug Interactions. London: Pharmaceutical Press, 1999;
Watanabe H, Kakihana M, Ohtsuka S, Sugishita Y. Randomized, double-blind,
placebo-controlled study of ascorbate on the preventive effect of nitrate
tolerance in patients with congestive heart failure. Circ.
Watanabe H, Kakihana M, Ohtsuka S, Sugishita Y. Randomized, double-blind,
placebo-controlled study of the preventive effect of supplemental oral vitamin C
on attenuation of development of nitrate tolerance. J Am Coll Cardiol.
Whitney E,Cataldo C, Rolfes S. Understanding Normal and Clinical
Nutrition. St. Paul, Minn: West Publishing Co; 1987.
Zamah N, Humpel M, Kuhnz W, Louton T, et al. Absence of an effect of high
vitamin C dosage on the systemic availability of ethinyl estradiol in women
using a combination oral contraceptive. Contraception.
Copyright © 2007 Drugs Area
This publication contains
information relating to general principles
of medical care that should not in any event be construed as specific
instructions for individual patients. The publisher does not accept any
responsibility for the accuracy of the information or the consequences arising
from the application, use, or misuse of any of the information contained herein,
including any injury and/or damage to any person or property as a matter of
product liability, negligence, or otherwise. No warranty, expressed or implied,
is made in regard to the contents of this material. No claims or endorsements
are made for any drugs or compounds currently marketed or in investigative use.
The reader is advised to check product information (including package inserts)
for changes and new information regarding dosage, precautions, warnings,
interactions, and contraindications before administering any drug, herb, or
supplement discussed herein.