Vitamin C

Definition

Vitamin C—or ascorbic acid—is probably the best-known of all vitamins. It is water-soluble and can neither be made nor stored by the body. Thus, humans must obtain a steady supply of vitamin C from foods in their diet in order to prevent the devastating disease known as scurvy.

Purpose

Vitamin C has essential roles in the human body, both as a coenzyme or cofactor that is required for the activity of various enzymes and also as a powerful antioxidant that helps protect cells from damage from free radicals and other active oxygen species that are both produced during normal metabolism and that enter the body from the environment. Vitamin C is required as a coenzyme in the production of collagen, which is a major component of the skin, blood vessels, cartilage, bones, teeth, tendons, and ligaments. Thus, vitamin C is necessary for the growth, maintenance, and repair of tissues throughout the body, as well as for wound healing and the formation of scar tissue. Vitamin C is a necessary coenzyme for the production of neurotransmitters that move signals between nerve cells, and it is necessary for metabolizing storage molecules into energy. As an antioxidant, vitamin C helps protect against free radicals that are responsible for aging and are involved in many diseases and conditions, including cancer, heart disease, and arthritis.

Vitamin C

Age

Recommended dietary allowance (mg)

Tolerable upper intake level (mg)

Children 0-6 mos.

40 (AI)

Not established

Children 7-12 mos.

50 (Al)

Not established

Children 1-3 yrs.

15

400

Children 4-8 yrs.

25

650

Children 9-13 yrs.

45

1,200

Boys 14-18 yrs.

75

1,800

Girls 14-18 yrs.

65

1,800

Men 19≥ yrs.

90

2,000

Women 19≥ yrs.

75

2,000

Men who smoke

125

2,000

Women who smoke

110

2,000

Pregnant women 18≤yrs.

80

1,800

Pregnant women 19≥yrs.

85

2,000

Breastfeeding women 18≤yrs.

115

1,800

Breastfeeding women 19≥yrs.

120

2,000

AI = Adequate intake

mg = milligram

SOURCE: Office of Dietary Supplements. National Institutes of Health. “Vitamin C: Fact Sheet for Health Professionals.” https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional (accessed April 19, 2018).

There are many claims for the benefits of large doses of vitamin C taken as dietary supplements, including prevention of everything from the common cold to cancer and heart disease; however, these claims remain unproven. High doses of vitamin C may be used to treat or prevent urinary tract infections, since high levels of vitamin C increase the acidity of urine, creating an inhospitable environment for bacteria in the urinary tract.

Description

Vitamin C, the essential nutrient that prevents scurvy, was isolated in 1932. By 1934, the pharmaceutical company Hoffman-La Roche had produced a synthetic version of vitamin C. The symptoms of scurvy were described as early as 1550 BCE by the ancient Egyptians. In 1540, the French explorer Jacques Cartier learned from Native Americans to treat scurvy with a hot-water extract of pine needles. Early Spanish explorers planted orange trees in Florida and the Caribbean to provide a source of citrus fruit for their long voyages back to Europe. By the mid-eighteenth century, the Edinburgh physician James Lind had proved that oranges and lemons could prevent and cure scurvy, which was still decimating crews on the long voyages of discovery, and eventually British ships began stocking lemon juice. Nevertheless, between 1500 and 1800, as many as two million sailors died of scurvy, and the disease continued to afflict armies at war, miners of the California Gold Rush, polar explorers, and civilian populations during times of famine.

Although all animals require vitamin C, most can make their own. Only humans, along with apes, guinea pigs, and a few other animals, have lost the ability to make vitamin C. Not only are humans unable to produce vitamin C, it cannot be stored in the body. As a water-soluble vitamin, any amount that is not used immediately is excreted in the urine. Nor is vitamin C evenly distributed throughout the body. The adrenal glands, pituitary gland, thymus, retina, brain, spleen, lungs, liver, thyroid, testicles, lymph nodes, kidney, and pancreas all contain much higher levels of vitamin C than are found in circulating blood.

Vitamin C's role in health




Subcutaneous bleeding over the shins of a person suffering from scurvy, a disease caused by a deficiency of vitamin C (ascorbic acid).





Subcutaneous bleeding over the shins of a person suffering from scurvy, a disease caused by a deficiency of vitamin C (ascorbic acid).
(ST. MARY'S HOSPITAL MEDICAL SCHOOL/Science Source)

Antioxidants such as vitamin C react with and deactivate free radicals. Free radicals are formed during normal cellular metabolism and during exposure to ultraviolet light and toxins such as cigarette smoke. Free radicals cause damage by oxidizing DNA, as well as fats and proteins in cell membranes. It is the antioxidant properties of vitamin C that are the basis for many of the controversial health claims for the benefits of large vitamin C doses.

Normal vitamin C requirements

The Institute of Medicine (IOM) of the U.S. National Academy of Sciences has developed dietary reference intake (DRI) values for vitamins and minerals. The DRIs consist of three sets of numbers. The recommended dietary allowance (RDA) defines the average daily amount of a nutrient needed to meet the health needs of 97%–98% of the population. The adequate intake (AI) is an estimate set when there is not enough information to determine an RDA. The tolerable upper intake level (UL) is the average maximum amount that can be taken daily without risking negative side effects. The AIs, RDAs, and ULs for vitamin C are in milligrams (mg) as follows:

These RDAs and ULs set by the IOM are controversial, since they are based on the amount of vitamin C necessary for preventing scurvy. Some researchers believe that doses many times higher— 400–3,000 mg per day for healthy adults—are needed to prevent certain chronic diseases. Furthermore, it is generally accepted that some people, in addition to pregnant and breastfeeding women, require higher doses of vitamin C. The recommended RDAs are 125 mg for men who smoke and 110 mg for women who smoke. People recovering from surgery, cancer patients, and burn victims may also require higher doses of vitamin C.

Sources of vitamin C

People need a continuous supply of vitamin C in their diet. This is not difficult for most Americans, since vitamin C is found in many foods. Citrus fruits and their juices, cantaloupe, kiwi fruit, mangoes, pineapples, raspberries, blueberries, cranberries, and watermelons are rich sources of vitamin C from fruit. Other good fruit sources include:

Among vegetables, Brussels sprouts; green peppers; leafy greens including spinach, cabbage, and turnip greens; and winter squash are rich in vitamin C, as are:

KEY TERMS
Adequate intake (AI)—
The daily average intake level of a nutrient that is likely to be adequate for a healthy, moderately active individual, as determined by the U.S. Institute of Medicine.
Antioxidant—
Substances, such as vitamin C, that prevent or reduce cellular damage from reactive oxygen species such as free radicals.
Coenzyme—
Cofactor; a small molecule that binds to an enzyme and promotes enzyme-mediated reactions.
Collagen—
A fibrous protein found in skin, bones, blood vessels, and connective tissues such as tendons and ligaments.
Dietary reference intake (DRI)—
A system of nutritional recommendations used by the Institute of Medicine of the U.S. National Academy of Sciences and the U.S. Department of Agriculture.
Dietary supplement—
A product, such as a vitamin, mineral, herb, amino acid, or enzyme, that is consumed in addition to the diet with the expectation that it will maintain or improve health.
Enzymes—
Proteins that direct and promote chemical reactions in the body.
Fortified—
Having added nutrients, such as vitamin C, that do not occur naturally in that particular food.
Free radicals—
Reactive atoms or groups of atoms that damage cells, proteins, and DNA.
Neurotransmitters—
Chemicals that transmit signals between nerve cells (neurons), including dopamine, epinephrine, and norepinephrine.
Recommended dietary allowance (RDA)—
The approximate amount of a nutrient that should be ingested daily.
Scurvy—
A potentially fatal condition caused by vitamin C deficiency.
Tolerable upper intake level (UL)—
The highest daily intake level of a nutrient that is unlikely to cause adverse health effects in almost all individuals in the general population, as determined by the U.S. Institute of Medicine.
Water-soluble vitamin—
A vitamin that dissolves in water and can be removed from the body in urine.

The best sources of vitamin C are fresh, raw fruits and vegetables. Vitamin C is unstable and is lost when food is exposed to air, temperature changes, or water. About one-quarter of the vitamin C content of vegetables is lost by brief boiling, steaming, or freezing and thawing. Canning fruits and vegetables reduces their vitamin C content by about one-third, as does longer cooking at higher temperatures. Microwaving or steaming foods may preserve more of their vitamin C. Storing foods for long periods also reduces their vitamin C content.

Americans take more vitamin C than any other dietary supplement. As a single-ingredient supplement, vitamin C is available as tablets, capsules, and powders. It is also found in multivitamin and antioxidant supplements. It may be combined with minerals such as calcium to make it less acidic and thus less irritating to the stomach in large doses. Vitamin C can be produced synthetically or derived from corn or palm oil (ascorbyl palmate). There is little evidence that one form is more effective than another. In addition, some cereals and other processed foods and beverages are fortified with vitamin C. Vitamin C is added to some skin creams, throat lozenges, energy drinks, and energy bars. Nevertheless, both the American Cancer Society and the American Heart Association recommend that people meet their vitamin C (and most other vitamin) requirements through a healthy diet that includes a minimum of five servings of fruits and vegetables daily.

Vitamin C deficiency

As little as 10 mg per day of vitamin C is enough to prevent scurvy, and the disease is rare throughout most of the world. However, poverty can put anyone at risk for scurvy. It is epidemic in some refugee camps and remains a problem among the malnourished and populations that subsist primarily on grains.

In the United States, scurvy primarily affects alcoholics and older, malnourished adults, especially men suffering from “widower scurvy.” Babies between the ages of 6 and 18 months are sometimes affected if they are fed a diet that is deficient in fruits and vegetables or fortified foods. Nevertheless, some researchers believe that a significant sector of the American population may suffer from some degree of vitamin C deficiency. Smoking increases the body's need for vitamin C, but is not, by itself, a cause of scurvy.

Signs and symptoms of vitamin C deficiency include fatigue; easy bruising; excessive bleeding, especially from the nose and gums; tooth loss; hair loss; and swollen, painful joints. Scurvy can also cause anemia; susceptibility to infection; poor wound healing; dry and splitting hair; rough, scaly, and dry skin; and possible weight gain due to slowed metabolism. Scurvy causes malformed bones in children. If left untreated, scurvy is fatal, usually through sudden cardiac arrest.

Health claims for vitamin C

During the 1970s, the Nobel prize-winning chemist Linus Pauling popularized the idea that large doses (1,000 mg or more) of daily vitamin C could prevent, shorten the duration of, or reduce the severity of symptoms of the common cold. However, a multitude of studies have found little effect of large doses of vitamin C on the frequency or severity of colds. A few small studies have suggested that the amount of vitamin C in a typical multivitamin may ease cold symptoms, but there is little evidence that megadoses either prevent colds or ease symptoms in most people.

Most other claims for the health benefits of large vitamin C doses have also failed to be substantiated in well-designed, well-controlled studies. Studies of the effects of vitamin C supplements on heart disease, cancer, and eye diseases such as cataracts and macular degeneration have not been definitive. Although many studies have demonstrated that diets low in fats and high in fresh fruits and vegetables reduce the risk of heart disease and various cancers, there is little evidence that these benefits are due in large part to the antioxidant effects of vitamin C. Likewise, studies have not shown that supplemental vitamin C reduces blood levels of cholesterol or improves cardiovascular health. Other health claims for vitamin C— including prevention or treatment of lead poisoning, high blood pressure (hypertension), asthma, Alzheimer's disease, attention deficit hyperactivity disorder (ADHD), infertility, stomach ulcers, autism, premature birth, and a multitude of other conditions—remain unproven.

Precautions

Although Vitamin C can usually be taken in enormous doses without any serious side effects, large amounts of vitamin C can cause indigestion or diarrhea, which disappears when the dose is reduced.

Interactions

Vitamin C rarely interacts with drugs or other supplements. Large doses increase the amount of iron absorbed from food by the small intestine, although this is not normally harmful. Large daily doses of vitamin C may interfere with vitamin B12 absorption.

QUESTIONS TO ASK YOUR DOCTOR

Complications

Even very large doses of vitamin C rarely cause complications other than possible diarrhea.

Parental concerns

Parents generally do not need to be concerned about their children getting either too much or too little vitamin C. Vitamin C is safe for women during pregnancy and breastfeeding and passes into breast milk. Children under age one should get all of their vitamin C from breast milk, fortified formula, or foods. They should not be given supplemental vitamin C.

See also ADHD diet ; AIDS/HIV diet and nutrition ; Alcohol consumption ; Antioxidants ; Artificial preservatives ; Dietary supplements ; Iron ; Oral health and nutrition ; Osteoporosis diet ; Vitamins .

Resources

BOOKS

Aydogan, Müfide, and Asli Korkmaz. Does Vitamin C Act as an Antioxidant or Prooxidant? New York: Nova Biomedical Science, 2010.

Cohen, Suzy. Drug Muggers: Which Medications Are Robbing Your Body of Essential Nutrients—and Natural Ways to Restore Them. Emmaus, PA: Rodale, 2011.

Combs, Gerald F., and James P. McClung. The Vitamins: Fundamental Aspects in Nutrition and Health. 5th ed. Boston: Elsevier/Academic Press, 2017.

Davis, Robert J. Coffee Is Good for You: From Vitamin C and Organic Foods to Low-Carb and Detox Diets, the Truth about Diet and Nutrition Claims. New York: Penguin, 2012.

Francis-Cheung, Theresa. The Lemon Juice Diet. New York: St Martin's, 2010.

Herrmann, Wolfgang, and Rima Obeid, eds. Vitamins in the Prevention of Human Diseases. New York: Walter de Gruyter, 2011.

Jackson, Christina M., ed. Vitamin C: Nutrition, Side Effects, and Supplements. Hauppauge, NY: Nova Science, 2011.

Kroner, Zina. Vitamins and Minerals. Santa Barbara, CA: Greenwood, 2011.

Stone, Gene. The Secrets of People Who Never Get Sick. New York: Workman, 2010.

PERIODICALS

“The ‘Cement’ That Keeps the Body Together: Vitamin C and the Elixir of Life/Vitamin C May Inhibit AIDS Virus.” Nutrition Health Review 107 (July 2012): 12.

Marble, Steve. “Blind Faith across the Years; Following a Nobel Winner's Advice on Vitamin C—Just in Case.” Los Angeles Times, February 21, 2012, A2.

WEBSITES

Harvard T.H. Chan School of Public Health. “Vitamin C.” The Nutrition Source, Department of Nutrition, Harvard University. http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/vitamin-c (accessed April 22, 2018).

Kraemer, Carl M., et al. “Vitamin C (Ascorbic Acid).” Medscape. Updated October 6, 2017. http://emedicine.medscape.com/article/2088649-overview#showall (accessed April 22, 2018).

MedlinePlus. “Vitamin C.” U.S. National Library of Medicine, National Institutes of Health. https://medlineplus.gov/vitaminc.html (accessed April 22, 2018).

Office of Dietary Supplements. “Fact Sheet for Health Professionals: Vitamin C.” National Institutes of Health. https://ods.od.nih.gov/factsheets/VitaminC-Health-Professional/ (accessed April 22, 2018).

U.S. Department of Agriculture, National Agricultural Library. “DRI Tables and Application Reports.” Food and Nutrition Information Center. https://www.nal.usda.gov/fnic/dri-tables-and-application-reports (accessed March 15, 2018).

ORGANIZATIONS

Academy of Nutrition and Dietetics, 120 South Riverside Plaza, Ste. 2000, Chicago, IL, 60606-6995, (312) 899-0040, (800) 877-1600, http://www.eatright.org .

Food and Nutrition Information Center, National Agricultural Library, 10301 Baltimore Ave., Rm. 105, Beltsville, MD, 20705, (301) 504-5414, Fax: (301) 504-6409, fnic@ars.usda.gov, http://fnic.nal.usda.gov .

Linus Pauling Institute, Oregon State University, 307 Linus Pauling Science Center, Corvallis, OR, 97331, (541) 737-5075, Fax: (541) 737-5077, lpi@oregonstate.edu, http://lpi.oregonstate.edu/infocenter .

Office of Dietary Supplements, National Institutes of Health, 6100 Executive Boulevard, Room 3B01, MSC 7517, Bethesda, MD, 20892-7517, (301) 435-2920, Fax: (301) 480-1845, ods@nih.gov, http://ods.od.nih.gov .

Vitamin C Foundation, PO Box 130130, Spring, TX, 77393, (281) 255-3679, (800) 894-9025, Fax: (630) 416-1309, vitaminCFoundation@att.net, http://www.vitamincfoundation.org .

Tish Davidson, AM
Revised by Margaret Alic, PhD

  This information is not a tool for self-diagnosis or a substitute for professional care.