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vitamin C

What can high-vitamin C foods do for you?

  • Help protect cells from free radical damage
  • Lower your cancer risk
  • Regenerate your vitamin E supplies
  • Improve iron absorption

What events can indicate a need for more high-vitamin C foods?

  • Poor wound healing
  • Frequent colds or infections
  • Lung-related problems

Excellent sources of vitamin C include: parsley, broccoli, bell pepper, strawberries, oranges, lemon juice, papaya, cauliflower, kale, mustard greens, and brussels sprouts.

Description

What is vitamin C?

Because of its widespread use as a dietary supplement, vitamin C may be more familiar to the general public than any other nutrient. Studies indicate that more than 40% of older individuals in the U.S. take vitamin C supplements; and in some regions of the country, almost 25% of all adults, regardless of age, take vitamin C. Outside of a multivitamin, vitamin C is also the most popular supplement among some groups of registered dietitians, and 80% of the dietitians who take vitamin C take more than 250 milligrams. Why is this nutrient so popular?

Vitamin C, also called ascorbic acid, is a water-soluble nutrient that is easily excreted from the body when not needed. It's so critical to living creatures that almost all mammals can use their own cells to make it. Humans, gorillas, chimps, bats, guinea pigs and birds are some of the few animals that cannot make vitamin C inside of their own bodies.

Humans vary greatly in their vitamin C requirement. It's natural for one person to need 10 times as much vitamin C as another person; and a person's age and health status can dramatically change his or her need for vitamin C. The amount of vitamin C found in food varies as dramatically as our human requirement. In general, an unripe food is much lower in vitamin C than a ripe one, but provided that the food is ripe, the vitamin C content is higher when the food is younger at the time of harvest.

How it Functions

What is the function of vitamin C?

Vitamin C serves a predominantly protective role in the body. As early as the 1700's, vitamin C was referred to as the "antiscorbutic factor," since it helped prevent the disease called scurvy. This disease was first discovered in British sailors, whose sea voyages left them far away from natural surroundings for long periods of time. Their body stores of vitamin C fell below 300 milligrams, and their gums and skin lost the protective effects of vitamin C. Recognizing limes as a good shipboard source of vitamin C, the British sailors became known as "limeys" for carrying large stores of limes aboard ship.

The protective role of vitamin C goes far beyond our skin and gums. Cardiovascular diseases, cancers, joint diseases and cataracts are all associated with vitamin C deficiency and can be partly prevented by optimal intake of vitamin C. Vitamin C achieves much of its protective effect by functioning as an antioxidant and preventing oxygen-based damage to our cells. Structures that contain fat (like the lipoprotein molecules that carry fat around our body) are particularly dependent on vitamin C for protection.

Deficiency Symptoms

What are deficiency symptoms for vitamin C?

Full-blown symptoms of the vitamin C deficiency disease called scurvy - including bleeding gums and skin discoloration due to ruptured blood vessels - are rare in the U.S. Poor wound healing, however, is not rare, and can be a symptom of vitamin C deficiency. Weak immune function, including susceptibility to colds and other infections, can also be a telltale sign of vitamin C deficiency. Since the lining of our respiratory tract also depend heavily on vitamin C for protection, respiratory infection and other lung-related conditions can also be symptomatic of vitamin C deficiency.

Toxicity Symptoms

What are toxicity symptoms for vitamin C?

There are very few research studies that document vitamin C toxicity at any level of supplementation, and there are no documented toxicity effects whatsoever for vitamin C in relation to food and diet. At high supplemental doses involving 5 or more grams of vitamin C, diarrhea can result from the fluid in the intestine becoming too concentrated ("osmotic diarrhea").

Large supplemental doses of vitamin C can also increase levels of uric acid in the urine, because vitamin C can be broken down into uric acid. However, it is not clear that increased uric acid in the urine can increase a person's risk of forming uric acid kidney stones.

Finally, vitamin C can increase a person's absorption of iron from plant foods; and persons who have health problems related to excess free iron in their cells may want to consider avoiding high supplemental doses of vitamin C. It is important to remember that all of the above toxicity-related issues involve vitamin C in supplemental form, not as it naturally occurs in food.

In 2000, the National Academy of Sciences set a Tolerable Upper Intake Level (UL) for vitamin C at 2,000 milligrams (2 grams) for adults 19 years or older.

Impact of Cooking, Storage and Processing

How do cooking, storage, or processing affect vitamin C?

Vitamin C is highly sensitive to air, water, and temperature. About 25% of the vitamin C in vegetables can be lost simply by blanching (boiling or steaming the food for a few minutes). This same degree of loss occurs in the freezing and unthawing of vegetables and fruits. Cooking of vegetables and fruits for longer periods of time (10-20 minutes) can result in a loss of over one half the total vitamin C content. When fruits and vegetables are canned and then reheated, only 1/3 of the original vitamin C content may be left. Consumption of vitamin C-rich foods in their fresh, raw form is the best way to maximize vitamin C intake.

Factors that Affect Function

What factors might contribute to a deficiency of vitamin C?

Poor intake of vitamin C-rich vegetables and fruits is a common contributor to vitamin C deficiency. In the U.S., one third of all adults get less vitamin C from their diet than is recommended by the National Academy of Sciences, and 1 out of every 6 adults gets less than half the amount recommended. Smoking and exposure to second hand smoke also increase the risk of vitamin C deficiency.

The body's immune and detoxification systems make special use of vitamin C, and overload in either of these systems can increase risk of deficiency. The immune system relies on a wide variety of mechanisms to help protect the body from infection, including white blood cells, complement proteins, and interferons; and vitamin C is especially important in the function of these immune components.

Vitamin C is also critical during the first phase of the body's detoxification process. This process occurs in many types of tissue, but it is especially active in the liver. When the body is exposed to toxins, vitamin C is often required for the body to begin processing the toxins for elimination. Excessive toxic exposure is therefore a risk factor for vitamin C deficiency.

Drug-Nutrient Interactions

What medications affect vitamin C?

Categories of drugs that can diminish the body's supply of vitamin C include oral contraceptives (birth control pills), NSAIDs (non-steroidal anti-inflammatory drugs including aspirin and acetaminophen), corticosteroids (like cortisone), sulfa drugs (often used as antibiotics or in cancer treatment), and barbituates.

Nutrient Interactions

How do other nutrients interact with vitamin C?

Vitamin C has significant interactions with several key minerals in the body.

Supplemental intake of vitamin C at gram-level doses can interfere with copper metabolism. Conversely, vitamin C can significantly enhance iron uptake and metabolism, even at food-level amounts.

Vitamin C also has important interactions with other vitamins. Excessive intake of vitamin A, for example, is less toxic to the body when vitamin C is readily available. Vitamin C is involved in the regeneration of vitamin E, and these two vitamins appear to work together in their antioxidant effect.

Health Conditions

What health conditions require special emphasis on vitamin C?

Most forms of cardiovascular disease, joint disease, cancer, eye disease, thyroid disease, liver disease, and lung disease require special emphasis on vitamin C intake. The process of aging itself requires special attention to vitamin C. In addition to these broader categories, several specific health conditions also require special emphasis on vitamin C. These specific health conditions include:

Form in Dietary Supplements

What forms of vitamin C are found in dietary supplements?

Dietary supplements typically contain vitamin C in the form of ascorbic acid. Because vitamin C is better absorbed in the presence of flavonoids, many supplement manufacturers also add flavonoids to their formulas.

Buffered versions of vitamin C are also commonly available. These buffered forms usually combine vitamin C with minerals like calcium, magnesium, or potassium. Buffered vitamin C may be helpful for individuals who have stomach sensitivity, or who are taking higher doses of the supplement.

Also widely available is a metabolite complex form of vitamin C, sold commercially under the trade name Ester-C(TM), in which ascorbic acid is combined with several of its naturally occurring metabolites including dehydroascorbate, threonate, and aldonic acids.

Food Sources

Introduction to Nutrient Rating System Chart

The following chart shows the foods which are either excellent, very good or good sources of this nutrient. Next to each food name you will find the following information: the serving size of the food; the number of calories in one serving; DV% (percent daily value) of the nutrient contained in one serving (similar to other information presented in the website, this DV is calculated for 25-50 year old healthy woman); the nutrient density rating; and the food's World's Healthiest Foods Rating. Underneath the chart is a table that summarizes how the ratings were devised. Read detailed information on our Nutrient Rating System.

Foods Ranked as quality sources of:
vitamin C
Food Serving
Size
Cals Amount
(mg)
DV
(%)
Nutrient
Density
World's
Healthiest
Foods Rating
Red Bell Peppers (sliced, raw) 1 cup 24.8 174.80 291.3 211.1 excellent
Parsley, Fresh 1 oz-wt 10.2 37.71 62.9 110.8 excellent
Broccoli (pieces, steamed) 1 cup 43.7 123.40 205.7 84.8 excellent
Cauliflower (boiled, drained) 1 cup 28.5 54.93 91.5 57.8 excellent
Strawberries, Fresh 1 cup 43.2 81.65 136.1 56.7 excellent
Lemons, Juice, Fresh 0.25 cup 15.3 28.06 46.8 55.2 excellent
Lettuce, Romaine 2 cup 15.7 26.88 44.8 51.4 excellent
Greens, Mustard, Boiled 1 cup 21.0 35.42 59.0 50.6 excellent
Brussels Sprouts, Boiled 1 cup 60.8 96.72 161.2 47.7 excellent
Papaya 1 each 118.6 187.87 313.1 47.5 excellent
Kale, Fresh, Boiled 1 cup 36.4 53.30 88.8 43.9 excellent
Greens, Turnip, Cooked 1 cup 28.8 39.46 65.8 41.1 excellent
Grapefruit 0.50 each 36.9 45.51 75.8 37.0 excellent
Kiwifruit 1 each 46.4 57.00 95.0 36.9 excellent
Cantaloupe 1 cup 56.0 67.52 112.5 36.2 excellent
Oranges 1 each 61.6 69.69 116.2 34.0 excellent
Cabbage (shredded, boiled) 1 cup 33.0 30.15 50.3 27.4 excellent
Tomato, Red, Raw, Ripe 1 cup 37.8 34.38 57.3 27.3 excellent
Chard, Boiled 1 cup 35.0 31.50 52.5 27.0 excellent
Collard Greens, Boiled, Drained 1 cup 49.4 34.58 57.6 21.0 excellent
Raspberries, Fresh 1 cup 60.3 30.76 51.3 15.3 excellent
Peppermint Leaves, Fresh 1 oz-wt 19.9 9.02 15.0 13.6 excellent
Asparagus, Boiled 1 cup 43.2 19.44 32.4 13.5 excellent
Celery, Raw 1 cup 19.2 8.40 14.0 13.1 excellent
Spinach (boiled, with salt) 1 cup 41.4 17.64 29.4 12.8 excellent
Cucumber, Raw 1 cup 13.5 5.51 9.2 12.2 very good
Fennel Bulb, Sliced, Raw 1 cup 27.0 10.44 17.4 11.6 excellent
Pineapple 1 cup 76.0 23.87 39.8 9.4 excellent
Watermelon 1 cup 48.6 14.59 24.3 9.0 excellent
Green Snap/String Beans, Boiled 1 cup 43.8 12.13 20.2 8.3 excellent
Cranberries, raw, whole 0.50 cup 23.3 6.41 10.7 8.3 excellent
Squash, Summer, All Varieties 1 cup 36.0 9.90 16.5 8.3 excellent
Cloves, Ground 2 tsp 14.2 3.56 5.9 7.5 very good
Squash, Winter, All Varieties 1 cup 80.0 19.68 32.8 7.4 very good
Basil, Ground 2 tsp 7.5 1.84 3.1 7.3 good
Pepper, Cayenne, Dried 2 tsp 11.2 2.72 4.5 7.3 good
Blueberries, Fresh 1 cup 81.2 18.86 31.4 7.0 very good
Carrots, Raw 1 cup 52.5 11.35 18.9 6.5 very good
Garlic 1 oz-wt 42.2 8.85 14.8 6.3 very good
Apricots, Raw 1 each 16.8 3.50 5.8 6.3 very good
Liver, Calf 4 oz-wt 187.1 35.16 58.6 5.6 very good
Sweet Potato (small, baked with skin) 1 each 95.4 17.06 28.4 5.4 very good
Plum 1 each 36.3 6.27 10.4 5.2 very good
Green Peas-Boiled 1 cup 134.4 22.72 37.9 5.1 very good
Onions, Raw 1 cup 60.8 10.24 17.1 5.1 very good
Oregano, Ground 2 tsp 9.2 1.52 2.5 5.0 good
Chili Peppers, Red, Dried 2 tsp 25.5 3.84 6.4 4.5 very good
Leeks, Boiled 0.50 cup 16.1 2.18 3.6 4.1 good
Potato, Baked, with Skin 1 cup 133.0 15.74 26.2 3.6 very good
Yam, Dioscorea species, Cubes, Cooked 1 cup 157.8 16.46 27.4 3.1 good
Banana 1 each 108.6 10.74 17.9 3.0 good
Apples 1 each 81.4 7.87 13.1 2.9 good
Beets, Boiled 1 cup 74.8 6.12 10.2 2.5 good
Mushrooms, Shiitake, Raw 8 oz-wt 87.2 5.98 10.0 2.1 good
Pear, Bartlett 1 each 97.9 6.64 11.1 2.0 good
Grapes, Concord 1 cup 61.6 3.68 6.1 1.8 good
Corn, Yellow, Boiled 1 cup 177.1 10.16 16.9 1.7 good
Avocado, All Varieties 1 cup 235.1 11.53 19.2 1.5 good
World's Healthiest
Foods Rating
Rule
excellent DV>=75% OR Density>=7.6 AND DV>=10%
very good DV>=50% OR Density>=3.4 AND DV>=5%
good DV>=25% OR Density>=1.5 AND DV>=2.5%

Public Health Recommendations

What are the current public health recommendations for intake of vitamin C?

In 2000, the National Academy of Sciences established the following Adequate Intake levels for vitamin C:

  • 0-6 months: 40 milligrams
  • 7-12 months: 50 milligrams

In 2000, the National Academy of Sciences established the following Recommended Dietary Allowances for vitamin C:

  • 1-3 years: 15 milligrams
  • 4-8 years: 25 milligrams
  • Males 9-13 years: 45 milligrams
  • Males 14-18 years: 75 milligrams
  • Males 19 years and older: 90 milligrams
  • Females 9-13 years: 45 milligrams
  • Females 14-18 years: 65 milligrams
  • Females 19 years and older: 75 milligrams
  • Pregnant females 18 years: 80 milligrams
  • Pregnant females 19 years and older: 85 milligrams
  • Lactating females 18 years: 115 milligrams
  • Lactating females 19 years and older: 120 milligrams

References

  • Carr AC, Frei B. Toward a new recommended dietary allowance for vitamin C based on antioxidant and health effects in humans. Am J Clin Nutr 1999;69(6):1086-1107.
  • Englard S, Seifter S. The biological functions of ascorbic acid. Ann Rev Nutr 1986;6:365-406.
  • Groff JL, Gropper SS, Hunt SM. Advanced Nutrition and Human Metabolism. West Publishing Company, New York, 1995.
  • Kurl S, Tuomainen TP, Laukkanen JA et al. Plasma vitamin C modifies the association between hypertension and risk of stroke. Stroke 2002 Jun;33(6):1568-73.
  • Levine M. New concepts in biology and biochemistry of ascorbic acid. N Engl J Med 1986;314:892-902.
  • Levine M, Cantilena CC, Dhariwal KR. Determination of optimal vitamin C requirements in humans. Am J Clin Nutr 1995;62(suppl):1347S-1356S.
  • Linder MC. Food quality and its determinants from field to table - growing food, its storage and preparation, Chapter 10. In: M Linder (ed) Nutritional biochemistry and Metabolism with clinical applications, Elsevier, New York, London, 1991;239-254.
  • Medeiros DM, Bock MA, Raab C, et al. Vitamin and mineral supplementation practices of adults in seven western states. J Am Diet Assoc 1989;89(3):383-386.
  • Reaven PD, Witztum JL. Oxidized low density lipoproteins in atherogenesis: role of dietary modification. Ann Rev Nutr 1996;16:51-71.
  • Subar A, Block G. Use of vitamin and mineral supplements. Am J Epidem 1990;132:1901-1011.
  • Worthington-Roberts B, Breskin M. Supplementation patterns of Washington State dietitians. J Am Diet Assoc 1984;84(7):795-800.

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