The Antioxidant Vitamin - Vitamin C
Wednesday, March 5th, 2008The Antioxidant Vitamin - Vitamin C - by Gary Null, Ph.D.
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diagnosis and treatment by a qualified, licensed professional.
In the 65 years since its discovery, vitamin C has come to be known as a “wonder worker.” It’s easy to see why: In addition to its role in collagen formation and other life-sustaining functions, vitamin C serves as a key immune system nutrient and a potent free-radical fighter. This double-duty nutrient has been shown to prevent many illnesses, from everyday ailments such as the common cold to devastating diseases such as cancer.
In the scientific world, the water-soluble vitamin C is known as ascorbic acid (meaning “without scurvy,” the disease caused by a vitamin C deficiency). We depend on ascorbic acid for many aspects of our biochemical functioning; yet human beings are among only a handful of animal species that cannot produce their own supply of vitamin C. Like these other animals, including primates and guinea pigs, we have no choice but to obtain this nutrient in our diet. Considering the many benefits vitamin C may provide, that mandate is deceptively simple.
How Does Vitamin C Function in the Body?
Much like the immune system itself, which operates at a cellular level, the hardworking vitamin C reaches every cell of the body. The concentration of vitamin C in both blood serum and tissues is quite high.1 In fact, this nutrient plays a major role in the manufacture and defense of our connective tissue, the elaborate matrix that holds the body together. It serves as a primary ingredient of collagen, a glue-like substance that binds cells together to form tissues.
Vitamin C helps some of our most important body systems. First and foremost, it helps the immune system to fight off foreign invaders and tumor cells. Vitamin C also supports the cardiovascular system by facilitating fat metabolism and protecting tissues from free radical damage, and it assists the nervous system by converting certain amino acids into neurotransmitters.
The skin, teeth and bones also benefit from vitamin C’s collagen-forming and invader-resisting properties; this vitamin contributes to the maintenance of healthy bones, the prevention of periodontal disease and the healing of wounds. It even serves as a natural aspirin, of sorts, by combating inflammation and pain, according to Formula For Life. It accomplishes this task by inhibiting the secretion of the prostaglandins that contribute to such symptoms.2
What Biochemical Processes Require Vitamin C?
Collagen metabolism. Most of us know collagen as the much-promoted ingredient in our facial moisturizers and hand lotions. But the use of collagen in beauty and skin products only hints at the importance of this protein. The very structure of the body - the skin, bones, teeth, blood vessels, cartilage, tendons and ligaments - depends on collagen. And the integrity of collagen, in tum, depends on vitamin C.
In a report on ascorbic acid in Vitamin Intake and Health, S.K. Gaby and V.N. Singh explain that collagen protein requires vitamin C for “hydroxylation,” a process that allows the molecule to achieve the best configuration and prevents collagen from becoming weak and susceptible to damage. Beyond that, they say, recent evidence indicates that vitamin C increases the level of procollagen messenger RNA. “Collagen subunits are formed within fibroblasts as procollagen, which is excreted into extracellular spaces. Vitamin C is required to export the procollagen molecules out of the cell. The final…structure of the collagen is formed after pieces of the procollagen are enzymatically cleaved,” state Gaby and Singh.3
Antioxidant functions. As a water-soluble antioxidant, vitamin C is in a unique position to “scavenge” aqueous peroxyl radicals before these destructive substances have a chance to damage the lipids. It works along with vitamin E, a fat-soluble antioxidant, and the enzyme glutathione peroxidase to stop free radical chain reactions.
Immune system functions. Vitamin C can enhance the body’s resistance to an assortment of diseases, including infectious disorders and many types of cancer. It strengthens and protects the immune system by stimulating the activity of antibodies and immune system cells such as phagocytes and neutrophils.4
Other processes. Vitamin C contributes to a variety of other biochemical functions. These include the biosynthesis of the amino acid carnitine and the catecholamines that regulate the nervous system. It also helps the body to absorb iron and to break down histamine, the inflammatory component of many allergic reactions.5
What Specific Locations in the Body does Vitamin C Affect?
Although vitamin C is found in every cell, it is especially useful in key parts of the body. These include the blood, the skin, the nervous system, the teeth and bones and glands such as the thymus, adrenals and thyroid.
What Foods are Good Sources of Vitamin C?
Large concentrations of vitamin C can be found in fruits such as oranges, grapefruits, tangerines, lemons, limes, papaya, strawberries and cantaloupe. Vitamin C and bioflavonoids - the watersoluble substances that help to protect your capillaries - are found in the white linings of these and other plants. Many vegetables also pack in vitamin C including tomatoes, broccoli, green and red bell peppers, raw lettuce and other leafy greens.
How Is It Absorbed in the Body?
Species that make their own vitamin C synthesize it in the liver from glucose. Unfortunately, humans must get their ascorbic acid from dietary sources. Vitamin C is absorbed by an active transport system located in the gut and then reabsorbed through the kidneys, explain Gaby and Singh. Since the absorption mechanisms in the gut and kidneys can reach a saturation point, it is better to take multiple doses of vitamin C throughout the day than one large dose.6
How Much Vitamin C is Needed to Prevent a Deficiency?
The classic deficiency state related to vitamin C is scurvy, a condition characterized by gum disease, pain in the muscles and joints, skin lesions, fatigue and bleeding. An adult needs 10 milligrams of vitamin C per day to prevent scurvy. This is the absolute minimum, however, and some studies have shown that a daily dose of 100 mg or more may be needed to maintain or maximize the body pool of vitamin C.7
Who is Likely to Require a Higher Quantity of Vitamin C?
Depending on genetics and life-style factors, some people may require more vitamin C than the average healthy adult to prevent the disruption of important biochemical reactions. The elderly, alcohol consumers, diabetics and smokers, for example, tend to be low in vitamin C. In their report, Gaby and Singh offer the following evidence of this relationship.8
The elderly. Elderly people are known to be lacking in vitamin C, primarily because their diet is poor. In a 1978 study, elderly people had only half the level of ascorbic acid in their blood plasma as did younger subjects. How much vitamin C do they need to make up for this deficit? According to two studies, men and women over age 65 need daily doses of 150 mg and 75 to 80 mg, respectively, to maintain a plasma level of 1.0 mg/dl.
Alcohol consumers. Many chronic drinkers lack an adequate level of vitamin C because they tend to eat poorly, according to Gaby and Singh. Research also shows that a large intake of alcohol can depress the concentration of ascorbic acid in plasma and increase urinary excretion of vitamin C. Therefore, one study suggests that doses of vitamin C - at 500 to 1,000 mg per day can aid in the treatment of alcoholism.
Diabetics. The tissues and organs of diabetics may be deprived of vitamin C, requiring them to consume more of the nutrient than does the average person. Vitamin C must compete with glucose to reach the tissues and organs through a common cellular transport system. An insufficient supply of insulin also can inhibit the transport of vitamin C to cells that require insulin for their glucose uptake.
Workers exposed to toxins. Studies also show that the blood levels of vitamin C may be low in workers who are exposed to occupational pollutants such as lead and coal tar.
Smokers. At this point, it is a well accepted fact in the scientific arena that cigarette smoke has a negative impact on the metabolism of vitamin C. According to the Journal of Clinical Nutrition, people who smoke have a much lower level of ascorbic acid in the blood than do nonsmokers. While the Food and Nutrition Board recommends that smokers consume 100 mg of vitamin C a day, they may need 200 mg or more to maintain the same concentration of serum ascorbate as a nonsmoker who gets 60 mg of vitamin C per day.9
How Does Vitamin C Aid the Immune System Defenses?
Vitamin C assists the immune system in two of its primary functions to rid the body of foreign invaders and to monitor the systems for any sign of tumor cells. It accomplishes these vital tasks by stimulating the production of white blood cells, primarily neutrophils, which attack foreign antigens such as bacteria and viruses. It also boosts the body’s production of both antibodies and interferon, the protein that helps protect us from viral invaders and cancer cells.10
As a constituent of collagen, vitamin C may contribute to our immune defenses in an even more fundamental way: our skin and the epithelial lining of the body’s orifices, both of which contain collagen, serve as our first line of defense against foreign invaders.11 They prevent these invaders from entering the body in the first place, where the immune system would have to go to war against them.
Beyond that, vitamin C acts against the toxic, mutagenic and carcinogenic effects of environmental pollutants by stimulating liver detoxifying enzymes. It also stimulates the production of PGE1, a prostaglandin which assists lymphocytes, the defender cells in our immune system.12