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Vitamin C (Ascorbic Acid)

En Español (Spanish Version)

Vitamin c image 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
  • Playing a major role in collagen formation
  • Aiding in amino acid metabolism and hormone synthesis
  • Assisting in the synthesis of a neurotransmitter, norepinephrine
  • 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) [miligrams per 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
  • Hair loss
  • 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
  • Abdominal cramps
  • Formation of kidney stones in susceptible people

Major Food Sources

Food Serving size Vitamin C content (mg)
Strawberries 1 cup 85
Broccoli, cooked ½ cup 51
Kiwi 1 medium 64
Orange 1 medium 70
Pepper, red, raw ½ cup 95
Broccoli, cooked ½ cup 51
Cantaloupe ½ cup 29
Tomato juice ¾ cup 33
Brussels sprouts, cooked ½ cup 48
Orange juice ¾ cup 62-93
Cabbage, cooked ½ cup 28
Tomato, raw 1 medium 17
Grapefruit ½ medium 38
Green peas, frozen, cooked ½ cup 8
Grapefruit juice ¾ cup 62-70
Spinach, cooked ½ cup 9
Green pepper, sweet, raw ½ cup 60
Potato, baked with skin 1 medium 17
Avocado 1 medium 24
Pineapple 1 cup 24
Cauliflower, raw ½ cup 26
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—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—Indigent individuals who prepare their own food; food faddists; and people with mental illness may not be able to prepare meals that contain a variety of foods to obtain sufficient 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.

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.
 

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References:

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