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Since the body cannot synthesize vitamin C itself, it must absorb it through food. Vitamin C is a water soluble vitamin that cannot be stored in body fat and is easily altered by air, light, and heat. Chemically speaking, vitamin C is L-ascorbic acid and its salts or ascorbates, the most common being sodium ascorbate and calcium ascorbate. 

Roles

What does vitamin C do? 

Vitamin C plays a critical role in: 

  • Manufacturing collagen (protein essential to the formation of connective tissue in skin, ligaments, and bone);
  • Maintaining the body’s immune function (natural defense system);
  • Activating wound scarring;
  • Building red blood cells;
  • Increasing the absorption of iron from plant sources;
  • Protecting cells against damage caused by free radicals (antioxidant effect).

Needs

Many experts believe the recommended dietary allowances of vitamin C set by health authorities are too low and should be increased to at least 200 mg to ensure optimum health and the prevention of certain diseases. 

A number of factors must be taken into account when analyzing individual needs: 

  • Women have higher levels of vitamin C in their blood than men, so their requirements should be lower;
  • Smokers and people exposed to secondhand smoke have lower concentrations of vitamin C in their blood than nonsmokers;
  • Pregnant women who smoke excessively or who consume large quantities of drugs or alcohol are likely to have higher vitamin C requirements;
  • People with kidney problems are more likely to suffer the adverse effects of too much vitamin C.

Recommended Dietary Allowances for Vitamin C: 

Age
Men (mg/day)
Women (mg/day)
0 to 6 months
40mg*
40mg*
7 to 12 months
50mg*
50mg*
1 to 3 years
15mg
15mg
4 to 8 years
25mg
25mg
9 to 13 years
45mg
45mg
14 to 18 years
75mg
65mg
19 and up
90mg
75mg
Smokers
125mg
110mg
Pregnant women
 
80 mg (18 years and under)
85 mg (19 years and up)
Nursing mothers
 
115 mg (18 years and under)
120 mg (19 years and up)

Source: Food and Nutrition Board, Institute of Medicine, Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids, 2000. 

This data reflects a consensus between Canadian and U.S. health authorities. 

*Due to a lack of sufficient scientific evidence, the authorities have established adequate intake (AI) amounts rather than recommended dietary allowances (RDAs).

Sources

Vitamin C is found in nearly 90% of colorful raw fruits and vegetables. Generally speaking, the recommended dietary allowance for vitamin C can be easily met by consuming at least five servings of fresh fruit and vegetables a day. The vitamin C contained in foods can be degraded by air, water, and heat. It is therefore recommended that such foods be consumed raw or cooked briefly in a small amount of water and eaten right away. It is also a good idea to check the best before date of fruit juices and select those with the farthest date. 

Food vitamin C quantities
Foods
Portion Size
Vitamin C
Guava
125ml (1/2 cup)
188mg
Pepper (red), raw or cooked
125ml (1/2 cup)
117-142mg
Papaya
153g (1/2 papaya)
94mg
Kiwi
1 medium sized
71mg
Orange
1 medium sized
70mg
Orange juice
125ml (1/2 cup)
48-62mg
Pepper (green), raw or cooked
125ml (1/2 cup)
51-60mg
Pineapple and grapefruit juice
125ml (1/2 cup)
41-58mg
Mango
1 medium sized
57mg
Broccoli, raw or cooked
125ml (1/2 cup)
42-54mg
Brussels sprouts, cooked
4 sprouts (80g)
52mg
Strawberries
125ml (1/2 cup)
49mg
Beets, cooked
125ml (1/2 cup)
45mg
Kohlrabi
125ml (1/2 cup)
45mg
Grapefruit, pink or white
1/2 fruit
39mg
Peas (green), cooked
125ml (1/2 cup)
38mg
Vegetable juice
125ml (1/2 cup)
34mg
Carambola (star fruit)
1 medium sized
31mg
Cantaloupe
125ml (1/2 cup)
29mg
Pineapple
125ml (1/2 cup)
28mg

Source: Health Canada, Canadian Nutrient File, versions 2001b and 2005; United States Department of Agriculture (USDA), National Nutrient Database for Standard Reference.

Deficiency

Cases of serious vitamin C deficiency are rare in the industrialized world, although such deficiency may appear in individuals whose diet is lacking in fruit and vegetables or in people with lower socioeconomic status. Vitamin C deficiency can also occur in drug addicts and alcoholics. 

NOTE: Scurvy is the age-old disease that results from serious vitamin C deficiency.

Signs of vitamin C deficiency:

  • Tiny red spots on the skin;
  • Bruising;
  • Corkscrew hair;
  • Painful joints;
  • Poor wound healing;
  • Teeth and skin problems (bleeding);
  • Weak muscles;
  • Fatigue and sometimes depression.

Indications

  • Cold and flu prevention among elite athletes who exert intense regular physical effort (proven effectiveness);
  • Cold and flu prevention and treatment among the general population (probably ineffective);
  • Cancer (uncertain effectiveness);
  • Heart disease (antioxidant effect) (uncertain effectiveness);
  • Asthma (uncertain effectiveness);
  • Cataracts (uncertain effectiveness);
  • Macular degeneration (uncertain effectiveness).

Adverse effects

Long term consumption of high doses of vitamin C supplements should be avoided in the following cases: 

  • Intestinal surgery;
  • Kidney failure accompanied by problems metabolizing vitamin C or oxalic acid;
  • Hemochromatosis (disease characterized by an accumulation of iron in certain organs, notably the liver, pancreas, heart, and pituitary gland);
  • G6PD deficiency (the most common deficiency worldwide), characterized by the destruction of red blood cells.

Signs of excess vitamin C (over 3,000 mg/day): 

  • Soft stools;
  • Diarrhea;
  • Gastro-intestinal problems;
  • Kidney stones (controversial).

Cons-indications

  • None known at generally recommended doses. 

Interactions

Natural health products or vitamin supplements:

  • none;

Drugs that can lower vitamin C levels in blood:

  • Oral contraceptives taken on a regular basis;
  • Anti-inflammatory drugs or ASA (aspirin) taken on a regular basis.

Additional information

Speak with your pharmacist if you plan to take vitamin C supplements. Your pharmacist can help you choose the solution that’s best for you based on your health and any drugs you take. 

Other names

Vitamin C, Ascorbic acid, Calcium ascorbate, Sodium ascorbate