Vitamin C, also called ascorbic acid, is a water-soluble vitamin. Water-soluble vitamins are stored in the body in very limited amounts, and are excreted through the urine. Therefore, it is a good idea to have them in your daily diet. Vitamin C is sensitive to light, heat, and air and can be destroyed during food preparation, cooking, or storage.
Vitamin C Toxicity
The tolerable upper intake level (UL) for vitamin C from dietary sources and supplements combined is:
- Ages 1-3: 400 mg/day
- Ages 4-8: 650 mg/day
- Ages 9-13: 1,200 mg/day
- Ages 14-18: 1,800 mg/day
- Ages 19+: 2,000 mg/day
Because excess vitamin C is excreted in the urine, toxicity is rare. It can happen though, with several large doses throughout the day. Symptoms of vitamin C toxicity include:
- Nausea
- Excessive urination
- Diarrhea
- Abdominal cramps
- Formation of kidney stones in susceptible people
Health Implications
Populations at Risk for Vitamin C Deficiency
The following populations may be at risk for vitamin C deficiency and may require a supplement:
- People who smoke cigarettes—Due to an increased metabolic turnover of vitamin C, smokers have lower blood vitamin C levels. It is recommended that smokers take 35 mg more per day than the applicable RDA.
- People who drink excessive amounts of alcohol—This may, in part, be due to a nutritionally inadequate diet.
- The elderly—Studies have shown that older adults have lower levels of serum vitamin C. This may be due to a diet lacking in essential nutrients.
- Infants—Feeding babies evaporated or boiled milk can cause
vitamin C deficiency. This is because heat can destroy the vitamin C found in cow's milk.
- People with limited variety in their diet—People whose diets are affected by poverty; food faddists; and people with mental illness may not prepare meals that contain a variety of foods to obtain enough vitamin C.
- People with malabsorption and certain chronic diseases—Those with certain medical conditions like severe intestinal malabsorption, renal disease, or cancer may not be able to absorb enough vitamin C.
Antioxidant Capabilities
Free radicals are normal by-products of metabolism, but they can cause chain reactions that result in cell damage. This cell damage can, in turn, increase the risk of chronic diseases, including certain forms of cancer and cardiovascular disease.
Antioxidants have the ability to stop this chain reaction. Vitamin C functions in the body as an antioxidant. Because of this antioxidant capability, vitamin C is being studied for a possible role in prevention of certain conditions like age-related macular degeneration, cataracts, cancer, and cardiovascular diseases. Currently there is not sufficient evidence to recommend vitamin C for any of these conditions.
Respiratory Infections
Many people believe that taking mega-doses of vitamin C will cure a
cold. There is no scientific evidence to support this idea in the general population. However, there may be some preventative benefit in people exposed to extreme physical stress, cold environments, or those not getting enough vitamin C normally. Studies have found that taking vitamin C daily may help slightly reduce the symptoms and the duration of a cold. But taking vitamin C after the onset of the cold does not appear to effect the course of the illness. In addition, a review of studies on vitamin C found that it may be able to prevent and treat pneumonia, particularly in people who do not get enough vitamin C in their diet.
