Vitamin C (Ascorbic Acid)
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.
Functions
Vitamin C's functions include:
-
Acting as an antioxidant in the body, protecting:
- Intracellular fluid
- Blood
- Interstitial fluid
- Plasma lipids
- LDL cholesterol
- Playing a major role in collagen formation
- Aiding in amino acid metabolism and hormone synthesis
- Assisting in the conversion of the amino acid tryptophan to the neurotransmitter serotonin
- Helping break down cholesterol and synthesize bile
- Playing a role in the absorption, metabolism, and utilization of other nutrients, such as folate, calcium, and iron
- Promoting healing of wounds and burns
Recommended Intake:
| Age Group (in years) |
Recommended Dietary Allowance
(mg/day) |
|
|---|---|---|
| Females | Males | |
| 1-3 | 15 | 15 |
| 4-8 | 25 | 25 |
| 9-13 | 45 | 45 |
| 14-18 | 65 | 75 |
| 14-18 Pregnancy | 80 | n/a |
| 14-18 Lactation | 115 | n/a |
| 19-50 | 75 | 90 |
| 19-50 Pregnancy | 85 | n/a |
| 19-50 Lactation | 120 | n/a |
| 50+ | 75 | 90 |
Smoking increases oxidative stress and metabolic turnover of vitamin C. Therefore, the RDA for smokers is increased by 35 mg/day. For example, if you are a 22-year-old female smoker, your RDA for vitamin C is 110 mg/day.
Vitamin C Deficiency
Intakes of less than 10 mg per day of vitamin C can result in scurvy. Symptoms of vitamin C deficiency include:
- Bleeding gums
- Easy bruising
- Impaired wound and fracture healing
- Joint pain and swelling
- Loose and decaying teeth
- Anemia
- Bone fragility
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
- Diarrhea
- Formation of kidney stones in susceptible people
Major Food Sources
| Food | Serving size |
Vitamin C content
(mg) |
|---|---|---|
| Strawberries | 1 cup | 95 |
| Papaya | 1 cup | 85 |
| Kiwi | 1 medium | 70 |
| Orange | 1 medium | 70 |
| Pepper, red or green, raw | ½ cup | 65 |
| Broccoli, cooked | ½ cup | 60 |
| Cantaloupe | ¼ medium | 60 |
| Kale, cooked | 1 cup | 55 |
| Brussels sprouts, cooked | ½ cup | 50 |
| Orange juice | ½ cup | 50 |
| Pepper, red or green, cooked | ½ cup | 50 |
| Mango | 1 cup | 45 |
| Grapefruit | ½ medium | 40 |
| Snow peas, fresh, cooked | ½ cup | 40 |
| Grapefruit juice | ½ cup | 35 |
| Artichoke, boiled | 1 medium | 30 |
| Sweet potato, baked with skin | 1 medium | 28 |
| Potato, baked with skin | 1 medium | 25 |
| Avocado | 1 medium | 24 |
| Pineapple | 1 cup | 24 |
| Cauliflower, raw | ½ cup | 23 |
| Snow peas, frozen, cooked | ½ cup | 20 |
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—Studies have shown that alcoholics have lower blood vitamin C concentrations. 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.
Antioxidant Capabilities
Free radicals are normal by-products of metabolism, but they can cause chain reactions that result in significant cell destruction. This cell destruction 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 chronic disease prevention.
Respiratory Infections
Many people believe that taking mega-doses of vitamin C will prevent or cure a cold. There is no scientific evidence to support this idea. However, studies have found that taking vitamin C daily (1,000 mg/day) may help slightly reduce the severity of symptoms and the duration of a cold. 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 in their diet.
Tips For Increasing Your Vitamin C Intake:
To help increase your intake of vitamin C:
- Serve fruits and vegetables raw whenever possible.
- Leave the skin on potatoes and sweet potatoes.
- Add sliced strawberries, mango, or kiwi to your breakfast cereal.
- Use mashed avocado in place of mayonnaise as a sandwich spread.
- Throw snow peas in your stir-fry.
- Replace your morning coffee with a glass of orange or grapefruit juice.
- If you take a vitamin supplement, make sure it contains vitamin C.
Resources:
American Dietetic Association
Harvard School of Public Health
Canadian Resources:
Canadian Digestive Health Foundation
Dietitians of Canada
References:
Food and Nutrition Information Center. US Department of Agriculture website. Available at: http://www.usda.gov/wps/portal/usdahome.
Groff JL, Gropper S. Advanced Nutrition and Human Metabolism. Belmont, CA: West Publishing Company; 1995.
"How much vitamin C do you need?" JAMA Patient Page. 1999;281.
Harrison RH, Somer E. The Nutrition Desk Reference. New Canaan, CT: Keats Publishing; 1995.
¹10/30/2009 DynaMed Systematic Literature Surveillance http://www.dynamicmedical.com/what.php: Hemila H, Louhiala P. Vitamin C for preventing and treating pneumonia. Cochrane Database Syst Rev. 2009;(3):CD005532.
Last reviewed June 2008 by Dianne Scheinberg MS, RD, LDN
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.