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Vitamin C kills bacteria directly and neutralizes bacterial toxins
by boosting our natural defenses, the immune system. 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 infection.
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 that increases resistance to all
types of infection and disease is a good reason for consuming adequate
amounts of vitamin C.
Vitamin C functions primarily to form collagen, the primary protein
used to make connective tissue and form scar tissue, and are needed
to form bone, and cartilage. This collagen, theorized by Mathias
Rath, M.D., helps to protect the heart's blood from attracting sticky
particles.
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. The risk for inflammation
of the lung tissue increases when vitamin C consumption is low.
Vitamin C is number one on the list of antioxidants employed as
a defense against cancer and is regarded as the most powerful anticarcinogenic
nutrient known. It blocks the creation of nitrosamine, a carcinogen.
Nitrosamine forms in the body from smoked and cured meats, tobacco,
as well as natural gastric secretions. Vitamin C supplementation
can therefore help prevent cancer of the stomach and gastrointestinal
tract. In addition, the risks of cancer of the breast, cervix, pancreas,
bladder, and esophagus can greatly be reduced with daily doses of
Vitamin C.
A low tissue concentration of vitamin C is a real risk factor for
heart disease. Since vitamin C protects blood fats from turning
into atherosclerotic plaque, it is a must for heart disease prevention.
Ascorbate prevents lipoproteins from oxidation, the process through
which this "bad" cholesterol builds up inside the arteries.
Also raising the HDL, high lipoprotein, which protects your arteries
from forming cholesterol.
Ascorbate helps to support the adrenal glands, which secrete the
hormones we need to function during stressful situations. The adrenals
contain more ascorbate than any other part of our body.
Vitamin C taken when dieting can help the process to be healthier
by ridding the body of toxic compounds that are released whenever
fat is metabolized. It supports the liver by enabling it to withstand
the free radical stress that weight loss imposes.
Vitamin C, in doses of 2 grams daily, has been shown to delay the
process of stone formation by 350 percent.
Eye health is improved and protected from daily doses of Vitamin
C. In addition to certain carotenoids, vitamin C's antioxidant action
can protect against cataracts and slow their growth. A minimum dose
of 800 mg. daily is required and should be taken with vitamin E
and beta-carotene. Vitamin C also reduces pressure within the eyes,
which decreases the risk of glaucoma.
Deficiency: Scurvy is a disease caused by vitamin
C deficiency. Symptoms are poor wound healing, soft and spongy bleeding
gums, edema, extreme weakness and pinpoint hemorrhages under the
skin. This condition is very rare in Western societies. Other signs
of deficiency include gums that bleed when brushed, susceptibility
to infection, (especially colds and bronchial infections), joint
pain, lack of energy, poor digestion, poor wound healing, bruising
easily, and tooth loss.
Depleting Agents: Aspirin, alcohol, antidepressant
drugs, analgesics, oral contraceptives, anticoagulants, steroids,
cooking, food processing, diuretics, air pollution, smoking, acetaminophen
toxicity.
Sources: Berries, citrus fruits, green vegetables,
avocados, beet greens, black currants, broccoli, Brussels sprouts,
cantaloupe, collards, dandelion greens, dulse, grapefruit, kale.
Lemons, mangos, mustard greens, onions, oranges, papayas, green
peas, sweet peppers, persimmons, pineapple, radishes, rose hips,
spinach, strawberries, Swiss chard, tomatoes, turnip greens, and
watercress. Eating vegetables raw, or minimally cooked, increases
their vitamin C content.
Herb sources: Alfalfa, burdock root, cayenne, chickweed,
eyebright, fennel seed, fenugreek, hops, horsetail, kelp, peppermint,
mullein, nettle, oat straw, paprika, parsley, pine needle, plantain,
raspberry leaf, red clover, rose hips, skullcap, violet leaves,
yarrow, and yellow dock.
Precautions: Vitamin C is considered nontoxic. Diabetes
medications such as chlorpropamide (Diabinese) and sulfa drugs may
not be as effective if taken with Vitamin C. Taking high doses of
Vitamin C may cause a false-negative reading in tests for blood
in the stool. Anyone who has a history of kidney stones should take
Vitamin C only with physician approval. Unusually excessive doses
may cause intestinal upset, gas or diarrhea. Diarrhea, gas, or other
intestinal disturbances are harmless and reversible with lower dosing.
Pregnant or nursing mothers should not use amounts larger than 5,000
mg. daily.
Dosage Ranges and Duration of Administration: 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.
A general recommendation 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.
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.
INTERACTIONS
Acetaminophen
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 1976).
Aspirin
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 1999).
Furosemide
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).
Isosorbide Dinitrate, Isosorbide Mononitrate, Nitroglycerin
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).
Nonsteroidal 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. 1996).
Oral Contraceptives
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
effect.
Propranolol
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 reach Cmax.
Tetracycline
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 effects.
Warfarin
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). |
