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Vitamin C — Benefits, Sources, Deficiency, and Daily Dosage

Article author photo Arpi Gasparyan by Arpi Gasparyan | Last updated on April 19, 2024
Medically reviewed by Victoria Mazmanyan Article author photo Victoria Mazmanyan

Vitamin C — Benefits, Sources, Deficiency, and Daily Dosage


Vitamin C, or L-ascorbic acid, is a water-soluble vitamin with potent antioxidant properties. It is found in fruits and vegetables. Vitamin C is required for collagen, L-carnitine, and catecholamine biosynthesis, dietary iron absorption, the prevention and treatment of scurvy, and more (1, 2, 3).


Absorption & Physiological Role

Most vitamin C is absorbed in the small intestine and regulated by specific dose-dependent active transporters. Vitamin C’s absorption decreases as its concentrations increase in the intestinal lumen. A second specific transporter accumulates vitamin C in cells.

According to in vitro studies, oxidized vitamin C, or dehydroascorbic acid, enters cells via several glucose transporters and is further converted to ascorbic acid (1, 3).

Approximately 70-90% of 30-180 mg of vitamin C can be absorbed daily, and less than 50% is absorbed in intakes above 1g daily. The unmetabolized vitamin C is excreted via the kidneys.

The total levels of vitamin C in the organism range from 300mg, considered near scurvy concentrations, to 2g. Most vitamin C is found in the cells and tissues, being the highest in white blood cells, eyes, adrenal and pituitary glands, and brain; low levels of vitamin C are found in plasma, red blood cells, and saliva (1).

Vitamin C is required for the biosynthesis of collagen, L-carnitine, catecholamines (norepinephrine or noradrenaline and epinephrine or adrenaline), protein metabolism, and immune function. It also promotes plant-based (nonheme) iron absorption and cholesterol conversion to bile acids. Vitamin C blocks oxidative damage to tissues and regenerates other antioxidants, such as Vitamin E (1, 4). 

Vitamin C is essential in procollagen hydroxylation of proline and lysine, a process necessary to form triple-helix mature collagen, an essential component of connective tissue. Low levels of stable triple-helix collagens affect the integrity of the skin, mucosa, blood vessels, and bones. Therefore, vitamin C deficiency leads to scurvy, the symptoms of which will be discussed below (1, 3, 5).

Recommended Intakes 

According to the 2020-2025 Dietary Guidelines for Americans, the recommended dietary allowance (RDA) of vitamin C is 75mg for adult women and 90mg for adult men (6).

The RDAs in the table below are calculated based on age, sex, pregnancy, and lactation (1, 6).

 2-3 years4-8 years9-13 years14-18 years19+ years

Food Sources

The main dietary sources of vitamin C are fruits and vegetables: potatoes, citrus fruits, tomatoes, and their juices are rich in vitamin C.

Other vitamin C-rich foods include bell peppers, kiwifruit, broccoli, strawberries, etc. Vitamin C may be artificially added to some breakfast cereals, which is labeled on the packaging.

Dietary sources of vitamin CAmount per serving size
Rose hips, wild (Northern Plains Indians)541mg in 127g (1 cup)
Kiwifruit137mg in 148g (1 NLEA serving)
Broccoli, raw132mg in 148g (1 NLEA serving)
Guava125mg in 55g (1 fruit)
Orange juice124 mg in 248g (1 cup)
Pomelo116g in 190g (1 cup)
Bell pepper, green95.7mg in 119g (1 medium pepper)
Strawberries86.4mg in 147g
Brussels sprouts, raw74.8g in 88g
Orange59.7mg in 131g (1 fruit)
Cauliflower, raw51.6mg in 107g (1 cup)
Grapefruit48mg in 154g
Tomatoes, ripe, raw20.3mg in 148g (1 NLEA serving)
Potatoes, baked14.2mg in 148g (1 NLEA serving)

You can visit “Foods high in Vitamin C” to learn about more vitamin C-rich foods based on their 100g servings.

Vitamin C is water-soluble and heat-sensitive; thus, it will be destroyed by heat during high temperatures and long cooking periods. In other cases, vitamin C might be leached into the cooking water. Steaming or microwaving may reduce losses (1, 7).


Vitamin C may be taken orally or administered intramuscularly, intravenously (IV), or subcutaneously (under the skin), mainly when malabsorption is suspected. Vitamin C may be diluted with saline or glucose to minimize the adverse reaction during the IV injection.

The daily intake of vitamin C is suggested to be 70 to 150 mg daily and increased to 300mg to 1g daily in severe deficiency (3).

Vitamin C & Human Health

Cardiovascular Health

Increased intake of fruits and vegetables might reduce the risk of heart disease due to their components with antioxidant properties. Vitamin C has been shown to decrease inflammatory changes in blood vessels, improve nitric oxide production, and widen blood vessels, preventing plaque instability in atherosclerosis (1, 8). 

However, the results of prospective studies are conflicting. For example, according to the 16-year prospective Nurses’ Health Study, over 85,000 female nurses who took dietary and supplemental vitamin C had a decreased risk of coronary heart disease, while those consuming only dietary vitamin C showed no significant associations. Furthermore, a smaller study of postmenopausal diabetic women taking 300mg of vitamin C supplements daily had an increased risk of heart disease mortality.

A prospective study of over 20,600 British adults showed that those with higher levels of vitamin C in the plasma had a 42% lower risk of stroke than those with lower levels.

A pooled analysis of several studies, including over 293,000 participants without cardiovascular disease, found that ≥700mg of daily vitamin C supplements decreased the risk of coronary heart disease by 25%. Nonetheless, a 2008 meta-analysis of ten years found that only dietary vitamin C is associated with a decreased risk of heart disease.

Most clinical intervention trials show that vitamin C supplementation might not affect heart disease risk (1, 9, 10). For example, in one study, over 8,000 women aged 40 or above with a history of heart disease were supplemented with 500mg of vitamin C daily for 9.4 years but showed no overall effect on heart events (1).

Low vitamin C intake might be inversely associated with systolic and diastolic blood pressures, noting that people with high blood pressure might have low serum vitamin C levels and benefit from supplementation (10).


Increased intake of fruits and vegetables is associated with a decreased risk of most cancer types (such as lung, breast, colorectal, prostate, stomach, esophageal, bladder, cervical, and endometrial cancers), partly due to their high vitamin C levels. In vivo, vitamin C has been shown to limit the formation of carcinogens due to its attenuated oxidative damage to the tissues, a risk factor for cancer (1, 11, 12).

However, the results are inconsistent. In a cohort of over 82,000 women of premenopausal ages, an intake of 205mg of dietary vitamin C daily was associated with a significantly lower risk of breast cancer among women with a family history of cancer. In contrast, many other studies find no strong associations between vitamin C intake and cancer risk.

One study, which included 13,000 healthy French adults who received antioxidant supplements with vitamin C, vitamin Ebeta-caroteneselenium, and zinc for 7.5 years, demonstrated a decreased incidence of total cancer in men but not women.

Vitamin C supplements alone or with other antioxidants showed no significant associations between prostate or total cancer risk in the Physicians’ Health Study II and the risk of esophageal or stomach cancers in a large intervention trial conducted in Linxian, China (1).

Oral administration of vitamin C can raise plasma levels to a maximum of 220micromol/L, whereas IV administration can increase them to 26,000micromol/L. This may be selectively toxic or harmful to tumor cells in vitro. However, further research is required to confirm the role of high-dose IV vitamin C as an anti-cancer drug (1).

People on chemotherapy treatment should avoid the intake of antioxidants, such as vitamin A, vitamin C, vitamin E, carotenoids, and coenzyme Q10, as they were reported to increase the risk of disease recurrence by 41% if the supplements were used before and during chemotherapy (13).

Eye Disease

Oxidative stress may be involved in the pathogenesis of two of the most common eye disorders and reasons for vision loss in the elderly—age-related macular degeneration (AMD) and cataracts. Thus, according to a hypothesis, vitamin C and other antioxidants may affect the development or treatment of these conditions. However, most prospective studies could not find direct associations between antioxidant intake and the prevention of early AMD, only suggesting it might help slow disease progression (1).

The AREDS trial evaluated the effect of several antioxidants (vitamin C, vitamin E, beta-carotene, zinc, and copper) on the development of advanced AMD in nearly 3,600 older adults for 6.3 years. Those at high risk of developing advanced AMD had a 28% lower risk of disease progression. A follow-up AREDS2 trial follow-up for 5 years confirmed the results.

A cohort study of over 30,000 Japanese individuals aged 45-65 linked higher dietary vitamin C intake with a reduced risk of developing cataracts. According to 2 case-control studies, vitamin C intake of >300mg/day may reduce the risk of cataract formation by 70-75%. Another study also noted that vitamin C supplements may delay the onset of cataracts after vitrectomy, occurring in up to 80% of people within 2 years (14). On the other hand, a cohort study of 24,500 Swedish women ages 49-83 noted that high-dose, but not lose-dose, vitamin C supplementation (1g daily) was associated with a 25% increased disease risk (1).

In the AREDS trials, those receiving supplements of 500mg of vitamin C, 400IU vitamin E, and 15mg of beta-carotene did not have a reduced risk of cataract development or progression. The AREDS2 trial confirmed these results (1).


Gout is arthritis that results from prolonged hyperuricemia (elevated serum uric acid levels), which leads to monosodium urate crystal deposition in the joints and soft tissues. Most epidemiological studies noted a correlation between increased vitamin C intake and lower uric acid levels in the blood (15, 16).

High levels of vitamin C positively affect purine metabolism and reduce serum uric acid levels, thus potentially reducing the risk of crystal deposition in joint structures and soft tissues. However, there is little evidence of vitamin C supplementation in the prevention and treatment of gout or its usefulness during symptom exacerbation. Most studies have short observation periods (15).

Common Cold

For a long time, it has been suggested that vitamin C intake might prevent or treat the common cold.  A 2007 Cochrane review examined several place-controlled trials. It demonstrated that prophylactic use of vitamin C did not significantly reduce the risk of the common cold in the general population but reduced cold incidence by 50% in marathon runners, skiers, and soldiers exposed to extreme physical exercise or cold environments (1).

Vitamin C intake after the onset of symptoms might slightly decrease the duration and severity of the common cold in some. However, a review of 29 trials failed to confirm that vitamin C intake shortened illness duration or the incidence (1, 17, 18, 19).

Vitamin C supplementation may also benefit older adults and chronic smokers (1).

Vitamin C Deficiency: Risk Groups, Scurvy & Symptoms

People at risk of vitamin C deficiency include (1, 20):

  • Smokers and passive smokers, due to increased oxidative stress in their organisms. Chronic smokers are advised to consume 35mg more vitamin C daily than nonsmokers.
  • Infants fed evaporated or boiled milk due to naturally low vitamin C levels in the milk and its destruction during heating.
  • Type 1 diabetics, potentially due to increased vitamin C requirements
  • Individuals with a limited intake of fruits and vegetables due to various reasons
  • Individuals with alcohol use disorder
  • People with impaired absorption, such as celiac disease, Crohn’s disease, cystic fibrosis
  • People with end-stage kidney disease or chronic hemodialysis
  • People with iron overload conditions.


Severe vitamin C deficiency causes scurvy, usually manifesting within a month of <10mg daily vitamin C intake. Low plasma vitamin C levels of <0.2mg/dL and 0mg/dL in leukocytes indicate scurvy, whereas >15mg/dL is sufficient (1, 20).

The first signs include inflammation of the gums, which leads to swelling, bleeding, and tooth loss, as well as fatigue and malaise. 

After some time, impaired collagen synthesis leads to connective tissue weakness, causing petechiae (bleeding spots under the skin and mucose), bruises, purpura (purple patches on the skin or mucosa), joint pain, poor wound healing, hyperkeratosis (skin thickening), corkscrew hairs, and swelling of lower extremities (1, 3, 20).

Iron deficiency or microcytic anemia may also be present, both due to decreased iron absorption and bleeding. Decreased bone mineral density during scurvy may lead to osteopenia, osteoporosis, bone resorption, fractures, dislocations, etc (1, 20).

Vitamin C Toxicity & Upper Intake Levels

Vitamin C has low toxicity and may lead to headache, dizziness due to IV use and diarrhea, nausea, vomiting, abdominal cramps, and other gut disturbances due to unabsorbed vitamin C’s osmotic effects. Daily intake of 6g of vitamin C may also lead to migraine headaches (1, 3).

Increased vitamin C intake may also increase the risk of kidney stone formation in those with a history of kidney stones.

Theoretically, a high vitamin C intake may lead to excess iron absorption; nonetheless, it is less likely to cause adverse effects in healthy individuals. Those with hereditary hemochromatosis should avoid consuming too much vitamin C, which may exacerbate iron overload and cause tissue damage (1).

The tolerable upper intake levels are shown in the table below (1).


 2-3 years4-8 years9-13 years14-18 years19+ years

Vitamin C Contraindications

Vitamin C supplementation is contraindicated for people with blood disorders such as thalassemia, G6PD deficiency, sickle cell anemia, and primary or secondary hemochromatosis (iron overload). Supplements should also not be taken before or after angioplasty. 

Those with diabetes should take vitamin C with caution, as it may raise blood sugar levels. People with oxalate kidney stones or nephrolithiasis may also cautiously use vitamin C, which acidifies the urine and increases the risk of cysteine, urate, and oxalate precipitation (3).

Vitamin C Interactions With Medications

  • Chemotherapy and radiation therapy. Some data suggest that antioxidants may protect cancer cells from radiation and chemotherapy, whereas other data suggest they may protect from therapy-induced damage. Individuals undergoing radiation or chemotherapy should consult with their oncologist before taking antioxidants.
  • Statins. Vitamin C and other antioxidants may attenuate the increase in HDL cholesterol levels caused by niacin-simvastatin (Zocor) therapy. Blood lipid levels should be monitored in those taking statin and antioxidant supplements (1).


Vitamin C, or L-ascorbic acid, is a water-soluble vitamin with potent antioxidant properties. It is found in fruits and vegetables, including potatoes, citrus fruits, tomatoes and their juices, bell peppers, kiwifruit, broccoli, and strawberries. However, heat during cooking can destroy vitamin C, or it can be leached into the cooking water.

Vitamin C is required for collagen, L-carnitine, and catecholamine biosynthesis, dietary iron absorption, and the prevention and treatment of scurvy.

The RDA of vitamin C is 75mg for adult women and 90mg for adult men.  

Smokers, passive smokers, infants fed evaporated or boiled milk, type 1 diabetics, individuals with limited dietary intakes, alcohol use disorder, impaired absorption, kidney disease, and hemochromatosis are at risk of vitamin C deficiency. Vitamin C deficiency leads to scurvy and increases the risk of iron deficiency anemia.

Vitamin C intake after the onset of common cold symptoms might slightly decrease the duration and severity in some. However, a review of 29  trials failed to confirm this statement.

Data provided by should be considered and used as information only. Please consult your physician before beginning any diet.