Vitamin C (Ascorbic Acid): Overview
Alternative Names: Ascorbic Acid.
Vitamin C use has been an alternative therapy for many years. Many doctors do not hesitate to recommend doses of 1 to 5gm or more per day. The Third National Health and Nutrition Survey, also called NHANES III, showed that 11% of nonsmoking women and 21% of nonsmoking men in the United States do not get enough vitamin C. (Article continues below…)
One of the most talked about vitamins in recent decades, vitamin C activity was first identified hundreds of years ago for it’s ability to prevent and treat scurvy. There are few conditions for which Vitamin C has not been promoted for, and in many cases had some effect. Essentially, ascorbic acid is the main water soluble anti-oxidant of the body. It is considered a vitamin in man because we cannot synthesize it. There are thousands of articles and hundreds of books describing the benefits of supplementation with ascorbic acid.
In contrast with the findings from epidemiologic studies based on foods, observational studies of nutrients consumed in supplements and recent experimental trials provide little support for a strong protective role for vitamins C or E against cancer. If vitamins C or E are indeed protective against cancer, that protection may derive from their consumption in complex mixtures with other nutrients and with other bioactive compounds as found in the matrix provided by whole foods.
One of the main objections to mega-dose vitamin C use has been the possibility of developing kidney stones from elevated oxalic acid levels in the urine. This myth has been slow to die. It turns out that elevated levels of oxalic acid seen in some urine samples of people taking vitamin C were misleading. The particular testing method used could not distinguish between oxalic acid and vitamin C, thus giving a false positive reading for oxalic acid. More accurate testing methods have shown there are no oxalic acid elevations in vitamin C users.
Urinary oxalate excretion generally does not increase significantly for both normal subjects and stone-formers with ascorbic acid supplementation unless doses exceed 6gm daily; however, oxalate excretion even at those high doses is still usually in the range achievable by dietary influences alone. The exceptions derive from anecdotal reports of a small number of cases and from one poorly controlled trial with unstated methodology and questionable assay techniques (Piesse JW. Nutritional factors in calcium-containing kidney stones with particular emphasis on vitamin C.) [Int Clin Nutr Rev 5(3): pp.110-29, 1985] A study did not find a correlation between a high daily intake of vitamin C or vitamin B6 and the risk of stone formation, even when consumed in large doses. [J Urol, 1996 Jun, 155:6, pp.1847-51]
Most ascorbic acid is synthesized by the oxidation of l-sorbose (usually derived from corn). High quality ascorbic acid will be 99% pure and contain no residues of corn. To get the maximum effect of ascorbic acid supplements, one should combine them with plant flavonoids. Flavonoids, the so-called vitamin P, have been shown to increase the effectiveness of ascorbic acid as well as direct its usage to the areas most needed.
The best sources of vitamin C are fruits and vegetables. Citrus fruits such as oranges, grapefruit, and tangerines are excellent sources. Other good natural sources of vitamin C are: broccoli, cabbage, brussels sprouts, tomatoes, green peppers, melons, cantaloupe, kiwifruit, strawberries, sweet peppers, potatoes with skin, and alfalfa sprouts.
Here are some guidelines for eating fruits and vegetables with a high vitamin C content: Choose fresh or frozen fruits and vegetables over canned products; cook vegetables only for a short time in a small amount of water; eat raw vegetables; eat sliced fruits and vegetables shortly after they’re cut; keep fruits and vegetables refrigerated, and eat them while they’re fresh.
Acerola is a small cherry-like fruit of the small shrub Malpighia glabra. As one of the richest natural sources of vitamin C, fruits have between 1-4.5% vitamin C. The dried extraction (usually about 10:1) of the fruit juice may have between 10-18% Vitamin C content, although many of the products on the market above 10% are adulterated with commercial asorbic acid. Acerola also contains such other vitamins as vitamin A, thiamin, riboflavin and niacin in similar proportions as other fruits.
Reasons for Use
It is not known for sure if mega doses of antioxidants, such as vitamin C, can help decrease the risk for chronic diseases. Much of the current information is conflicting. More research is needed. In a review of recent studies, it was suggested that an intake of 90mg per day provides the optimal health benefits related to heart disease and cancer.
High oral doses of vitamin C have been used safely for decades. If the amount you are using causes diarrhea, the dosage needs to be reduced. However, in some conditions, in order for vitamin C to be effective it has to be used in doses that come very close to causing diarrhea. Unless this “bowel tolerance” dose is found and maintained, the condition for which the vitamin C was recommended may not resolve. If you are consuming doses of vitamin C greater than perhaps 500mg per day, do not stop its use abruptly. It is best to taper your dose down over several days. A sudden reduction may result in a temporary deficit (“rebound scurvy“) and a negative influence on your resistance to infection.
The RDA for vitamin C is 75mg for women and 90mg men. The RDA for pregnant women is 85mg; women who breastfeed should consume 120mg per day. Several groups are recommending that 120-200mg should be considered the recommended daily intake.
Side-Effects; Counter-Indicators and Warnings
Consuming more than 2,000mg per day of vitamin C can cause stomach upset and diarrhea and possibly other adverse effects.
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