Vitamin C is also known as ascorbic acid which, in chemical terms, is a sugar essential for biochemical functions in the human body. It is the only water-soluble vitamin that is not part of the B complex. Since it is water-soluble, vitamin C cannot be stored in the body and fresh supplies are needed daily from food. Vitamin C is the least stable vitamin and is very sensitive to oxygen. Potency can be lost or reduced through exposure to heat, light or air.
Despite the fact that it is so widely researched, vitamin C has so many functions that their extent is not fully understood. It is clear, however, that the human body cannot survive without this nutrient.
Vitamin C is measured in milligrams (mg).
The most common food sources of vitamin C are citrus fruits such as oranges, lemons, limes and grapefruits. Richest natural sources are acerola cherries, rose hips, plums, blackcurrants, guavas, strawberries and gooseberries.
Vegetables such as parsley, broccoli, greens, tomatoes, sprouts, green peppers and watercress also contain significant quantities of vitamin C. Although potatoes contain only low levels of the nutrient, because they are often eaten in such high quantities they can provide a useful contribution to intake of the vitamin.
Vitamin C is absorbed directly from the gastro intestinal tract into the bloodstream. The amount absorbed depends directly on how much has been ingested. Small, regular intakes will ensure optimum absorption. Blood levels of vitamin C reach a maximum two to three hours after ingestion of a moderate sized meal. Vitamin C is eliminated from the system via the urine and perspiration. Most of the vitamin C content of a meal has been excreted within four hours.
The absorption and usage of ascorbic acid is greatly increased when the body is under physical or mental stress. When a normal human body is saturated with vitamin C, it contains approximately 5000 mg (5 g) of the nutrient, 30 mg of which will be concentrated in the adrenal glands.
A further 200 mg will be concentrated in extra cellular fluids and the rest distributed throughout the cells of the body, nourishing the muscles, organs, tendons and bones.
Absorption of vitamin C is significantly impaired by cigarette smoking, drinking alcohol or stress. Taking certain drugs such as antibiotics, cortisone, aspirin, some painkillers and the contraceptive pill can also deplete levels of the nutrient, as can carbon monoxide fumes and lead poisoning.
Vitamin C is the least stable of the water-soluble vitamins. It is easily destroyed by oxidation, i.e. exposure to air, light, heat and water and storage. Processing and cooking can substantially reduce the vitamin C content of foods. Pressure cooking, steaming or boiling for a short time with a small amount of water and using the freshest possible vegetables will help to ensure that the maximum amount of the nutrient is retained.
Deficiency symptoms of vitamin C can be varied. In the elderly or ill, the symptoms of scurvy can still be observed. They include bleeding, easy bruising, swollen gums and dry, scaly skin. Other signs of less serious deficiency include depression, hysteria, lack of resistance to infection, the appearance of little blood spots called petechiae under the skin’s surface, muscle and joint pain and loose teeth.
Certain sections of the population may be more at risk of deficiency because of an increased requirement for the nutrient:
- Pregnant and lactating women.
- The elderly, who may consume low levels of fresh fruit and vegetables and who require additional vitamin C for the production of collagen.
- Athletes and those in demanding, stressful situations, because of their depleted levels of vitamin C in the adrenal glands.
- Smokers
- Heavy drinkers of alcohol
- Those taking certain drugs on a regular basis, including steroids, aspirin, antibiotics, corticosteroids or the contraceptive pill
- People who have undergone or are preparing for surgery may benefit from increased intake of vitamin C to assist in the healing process.
Bioflavonoids are a group of substances which always occur naturally with vitamin C and which enhance its activity. They are biochemical substances that work synergistically but also in their own right.
Richest sources are citrus fruits (the skin and the pulp), apricots, cherries, grapes, green peppers, tomatoes and broccoli. Unlike vitamin C they are very stable, even in processed foods.
Vitamin C is also linked with fat-soluble vitamins such as the powerful antioxidants A and E and with some B vitamins because of its protective effect over these nutrients.