WHAT IS VITAMIN C?


Vitamin C, also known as ascorbic acid, is a water-soluble vitamin. Unlike most mammals and other animals, humans do not have the ability to make their own vitamin C. Therefore, we must obtain vitamin C through our diet. Vitamin C is a water-soluble vitamin, meaning that your body doesn’t store it. We have to get what we need from food, including citrus fruits, broccoli, and tomatoes.
You need vitamin C for the growth and repair of tissues in all parts of your body. It helps the body make collagen, an important protein used to make skin, cartilage, tendons, ligaments, and blood vessels. Vitamin C is needed for healing wounds, and for repairing and maintaining bones and teeth.
Vitamin C is an antioxidant, along with vitamin E, beta-carotene, and many other plant-based nutrients. Antioxidants block some of the damage caused by free radicals, substances that damage DNA. The build-up of free radicals over time may contribute to the aging process and the development of health conditions such as cancer, heart disease, and arthritis.
It’ s rare to be seriously deficient in vitamin C, although evidence suggests that many people may have low levels of vitamin C. Smoking cigarettes lowers the amount of vitamin C in the body, so smokers are at a higher risk of deficiency.
Signs of vitamin deficiency include dry and splitting hair; gingivitis (inflammation of the gums) and bleeding gums; rough, dry, scaly skin; decreased wound-healing rate, easy bruising; nosebleeds; and a decreased ability to ward off infection. A severe form of vitamin C deficiency is known as scurvy.
Low levels of vitamin C have been associated with a number of conditions, including high blood pressure, gallbladder disease, stroke, some cancers, and atherosclerosis, the build-up plaque in blood vessels that can lead to heart attack and stroke. Getting enough vitamin C from your diet — by eating lots of fruit and vegetables — may help reduce the risk of developing some of these conditions. There is no conclusive evidence that taking vitamin C supplements will help or prevent any of these conditions.
Biosynthesis in different species

Model of a vitamin C molecule. Black is carbon, red is oxygen, and white is hydrogen.
Function
Vitamin C is required for the synthesis of collagen, an important structural component of blood vessels, tendons, ligaments, and bone. Vitamin C also plays an important role in the synthesis of the neurotransmitter, norepinephrine. Neurotransmitters are critical to brain function and are known to affect mood. In addition, vitamin C is required for the synthesis of carnitine, a small molecule that is essential for the transport of fat into cellular organelles called mitochondria, where the fat is converted to energy. Research also suggests that vitamin C is involved in the metabolism of cholesterol to bile acids, which may have implications for blood cholesterol levels and the incidence of gallstones.
Vitamin C is also a highly effective antioxidant. Even in small amounts vitamin C can protect indispensable molecules in the body, such as proteins, lipids (fats), carbohydrates, and nucleic acids (DNA and RNA), from damage by free radicals and reactive oxygen species that can be generated during normal metabolism as well as through exposure to toxins and pollutants (e.g., cigarette smoke). Vitamin C may also be able to regenerate other antioxidants such as vitamin E. One recent study of cigarette smokers found that vitamin C regenerated vitamin E from its oxidized form.
Deficiency
Scurvy
Severe vitamin C deficiency has been known for many centuries as the potentially fatal disease, scurvy. By the late 1700s the British navy was aware that scurvy could be cured by eating oranges or lemons, even though vitamin C would not be isolated until the early 1930s. Symptoms of scurvy include bleeding and bruising easily, hair and tooth loss, and joint pain and swelling. Such symptoms appear to be related to the weakening of blood vessels, connective tissue, and bone, which all contain collagen. Early symptoms of scurvy like fatigue may result from diminished levels of carnitine, which is needed to derive energy from fat, or from decreased synthesis of the neurotransmitter norepinephrine. Scurvy is rare in developed countries because it can be prevented by as little as 10 mg of vitamin C daily . However, cases have occurred in children and the elderly on very restricted diets.
The Recommended Dietary Allowance (RDA)
In the U.S., the recommended dietary allowance (RDA) for vitamin C was revised in 2000 upward from the previous recommendation of 60 mg daily for men and women. The RDA continues to be based primarily on the prevention of deficiency disease, rather than the prevention of chronic disease and the promotion of optimum health. The recommended intake for smokers is 35 mg/day higher than for nonsmokers, because smokers are under increased oxidative stress from the toxins in cigarette smoke and generally have lower blood levels of vitamin C.
Recommended Dietary Allowance (RDA) for Vitamin C
Life Stage Age Males (mg/day) Females (mg/day)
Infants 0-6 months 40 (AI)
40 (AI)
Infants 7-12 months 50 (AI) 50 (AI)
Children 1-3 years 15 15
Children 4-8 years 25 25
Children 9-13 years 45 45
Adolescents 14-18 years 75 65
Adults 19 years and older 90 75
Smokers 19 years and older 125 110
Pregnancy 18 years and younger – 80
Pregnancy 19 years and older – 85
Breast-feeding 18 years and younger – 115
Breast-feeding 19 years and older – 120

Disease Prevention
The amount of vitamin C required to prevent chronic disease appears to be more than that required for prevention of scurvy. Much of the information regarding vitamin C and the prevention of chronic disease is based on prospective studies, in which vitamin C intake is assessed in large numbers of people who are followed over time to determine whether they develop specific chronic diseases.

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