Vitamin C is essential to keep the human body functioning. Among its many roles, it helps the body build and maintain tissues, allows communication between cells, and provides protection from harmful chemicals. Vitamin C is required to make collagen, a type of protein found in skin, bones, blood vessels, tendons and ligaments. In addition to collagen, vitamin C is involved in making hormones and neurotransmitters that allow cells to communicate with each other. Vitamin C also acts as an antioxidant, protecting cells from the harmful effects of chemicals in the body called free radicals.

The human body cannot make vitamin C, so people must get it from foods. Fruits and vegetables are the best sources of vitamin C, especially citrus fruits, broccoli and bell peppers. Vitamin C is also available in supplements. These may be recommended for people who do not consume enough in the diet or as part of a medical treatment. Vitamin C supplements are often promoted to fight the common cold and to prevent or treat cancer, but research to date has shown they have little to no proven effectiveness.

Vitamin C deficiency is rare in the United States because a balanced diet meets the body’s needs. When it does occur, symptoms may first cause bleeding gums and small red spots under the skin. The deficiency can progress to scurvy and may cause hemorrhaging, skin damage and tooth loss. Without treatment, scurvy may lead to death from heart failure or internal bleeding.

Vitamin C, also known as ascorbic acid, is an essential nutrient. This means that it is not stored in tissues and must be consumed regularly through the diet. When vitamin C is consumed in food, it is absorbed and moves freely through the body and cells to perform its many functions.

The body requires vitamin C to synthesize several chemical compounds involved in building tissues and cellular communication. These compounds include:

• Collagen. Connective proteins that provide the structural framework for building and maintaining tissues. Collagen helps make some tissues elastic (e.g., skin, blood vessels, tendons, ligaments) and others rigid (e.g., teeth, bones). Scar tissue is also made of collagen, which allows wounds to heal.
  
  
• Carnitine. Chemical responsible for transporting fatty acids within cells to the mitochondria of the cell, where they are metabolized for energy.
  
  
• Serotonin and norepinephrine. Neurotransmitters critical to stress response. They are also associated with behavior and mood.
  
  
• Thyroxin. Hormone involved in regulating the metabolic rate. In times of stress, additional thyroxin is released to increase the amount of energy available.
  
• Hemoglobin. Protein in red blood cells that transports oxygen. Vitamin C enhances iron absorption, which is necessary to synthesize hemoglobin.

In addition to helping the body synthesize compounds, vitamin C protects cells from the effects of free radicals. These highly reactive chemicals can damage DNA and proteins, which alters the function of cells. Vitamin C functions as an antioxidant, which reduces free radical reactivity and their ability to damage human tissues.

The U.S. National Academy of Sciences has established dietary reference intakes (DRIs) for vitamin C. DRIs provide the daily intake of vitamin C necessary to support a healthy body – based on age and gender (including whether women are pregnant or breastfeeding). Tolerable upper intake levels (UL) were also determined. Patients who consume more than the UL for vitamin C increase potential health risks. These recommendations are measured in milligrams per day (mg/day).

Vitamin C DRIs

*Adequate intakes are provided for infants. These values are the average amount consumed by each age group.

Cigarette smoke and chewing tobacco produce oxidants, which deplete the body’s stores of vitamin C. Patients who use these products should add 35 mg to the daily recommendation. Additional vitamin C is also suggested for those who are routinely exposed to secondhand smoke.

Humans are unable to make vitamin C and must get the vitamin through the diet. Cooking foods destroys portions of the vitamin, so the best sources are fresh, raw fruits and vegetables. Foods containing significant amounts of vitamin C include:

• Citrus fruits and juices (e.g., oranges, lemons, limes, grapefruit)
• Broccoli
• Bell peppers
• Kiwi
• Strawberries
• Cantaloupe
• Potatoes
• Sweet potatoes
• Cabbage
• Lettuce
• Tomatoes
• Brussels sprouts

In the United States, the average balanced diet fulfills the body’s requirements for vitamin C. If necessary, vitamin supplements are also available. Vitamin C is a common addition to multivitamins and is also available separately in tablets and powders.

Increasing vitamin C intake has been studied for its impact on health. Physicians may recommend supplements as part of the established treatments for a variety of conditions, including:

• Major surgery or extensive burns. Due to its role in collagen formation, vitamin C may reduce the time required for tissues to heal.
  
  
• Iron deficiency. Increasing vitamin C intake helps some patients absorb more iron from food sources.

Other uses of vitamin C have been proposed based on its role in the immune system and as an antioxidant. Research has yielded mixed results and study continues. These topics include:

• Common cold. Multiple scientific studies have shown limited benefits for this use. Patients who take vitamin C supplements may have slightly shorter colds than those who do not. There is no apparent difference in the number or severity of colds. Recently, a review of 30 studies involving 11,000 participants over several decades found little evidence that vitamin C supplementation is effective in preventing or shortening colds. However, the review did find some evidence that people enduring high periods of physical stress (such as during marathons or sub-arctic exercises) may have a reduced risk of cold if they take vitamin C supplements.
  
  
• Cancer prevention and treatment. Consuming fruits and vegetables containing vitamin C has been related to cancer prevention, but it is unknown if this is caused by the vitamin or other factors. Pill supplements alone have not been proven to be effective and studies continue into treating the disease with intravenous (I.V.) doses of vitamin C.

Proper amounts of vitamin C are required for the body to function. Having too little or too much vitamin C stresses tissues and, in extreme cases, can lead to death.

Because it is water soluble, excess vitamin C is usually excreted with urine and overdoses are rare. When they do occur, symptoms include nausea, abdominal cramps and diarrhea. Kidney stones may also result from overdoses of vitamin C, though this is most likely to occur in patients with kidney disease or a tendency toward gout.

Excessive vitamin C intake may also interact with medical treatments or conditions. Examples of these interactions include:

• Diabetes tests. May cause false positives and false negatives.

• Anticoagulants. Reduces the effectiveness of these medicines used to prevent recurring strokes.
  

• Iron excess. Increases absorption of iron and may worsen the symptoms of patients who already have too much in their bodies. People with the condition hemochromatosis are encouraged to discuss vitamin C use with their physician.

A deficiency of vitamin C affects the entire body and many of the symptoms reflect the body’s inability to synthesize collagen. Tissues may begin to break down, frequently starting with the capillaries. This causes the earliest signs of vitamin C deficiency – bleeding gums and small red spots under the skin (pinpoint hemorrhages). With time, symptoms become more severe and affect the patient’s ability to function.

Advanced vitamin C deficiency is called scurvy. Scurvy was a common problem during long sea voyages in previous centuries, when supplies of fresh fruit were limited. Since its cause was discovered, scurvy rarely occurs in the United States and other industrialized nations. Cases are often associated with general malnourishment due to restrictive diets or alcoholism. Possible signs and symptoms of scurvy include:

• Bleeding at hair follicles
• Rough, brown, scaly and dry skin
• Poor wound healing
• Bone pain and increased risk of fracture
• Loosened teeth
• Weakness and fatigue
• Increased incidence of infections
• Irritability
• Depression

Under a physician’s care, scurvy can be cured by correcting the vitamin C deficiency. For adults, supplements of 100 milligrams of vitamin C are given daily for one to two weeks. Treatment for infants and children varies with age, but usually includes vitamin C supplements or adding dietary sources (e.g., orange juice).

Treatment may also involve consulting a registered dietitian to ensure adequate vitamin C is consumed in the diet to prevent recurrence of the deficiency. Without treatment, scurvy may lead to death through sudden cardiac failure or internal bleeding.

Preparing questions in advance can help patients have more meaningful discussions with health professionals regarding their conditions. Patients may wish to ask their doctor or registered dietitian the following questions related to vitamin C:

1. How can I learn more about sources of vitamin C and how much I need each day?
   
   
2. Am I at risk for vitamin C deficiency?
   
   
3. What early symptoms of vitamin C deficiency should I watch for?
   
   
4. What are my treatment options if I need treatment for my vitamin C deficiency?
   
   
5. Are there sources of vitamin C other than citrus fruits?
   
   
6. Is it possible for me to consume too much vitamin C?
   
   
7. What are the risks of consuming excess vitamin C?
   
   
8. Should I consult a registered dietitian to reduce my risk of vitamin C deficiency or overdose? Can you recommend one?
   
   
9. Will taking vitamin C supplements reduce my chances of catching a cold?
   
   
10. How will taking vitamin C supplements affect my chances of developing cancer?
    
    
11. Should I be concerned about how exposure to secondhand smoke affects vitamin C in my body?