This article was compiled by Kayla Martin, CNS candidate and edited by Erika Krumbeck, ND.
How is vitamin C used in the body?
Vitamin C is one of the most well known and widely used vitamins. Vitamin C is a water-soluble vitamin, meaning it dissolves in water and travels through the body to various tissues, but isn’t effectively stored. Therefore, it must be consumed on a daily basis to ensure adequate intake.
Vitamin C is probably best known for its antioxidant properties that help control infections like the common cold. However, its functions are vast and include playing a role in neurotransmitter synthesis, the breakdown of xenobiotics, collagen synthesis, immune support, regulation of cellular nucleotides such as cAMP and CGMP, and carnitine synthesis.1 It acts as a cosubstrate for enzymes that contain copper or iron cofactors and indirectly supports the production of several hormones such as oxytocin, vasopressin, gastrin, and calcitonin.1
The pharmacological uses of vitamin C generally center around enhancing the immune system via promoting chemotaxis and the proliferation of immune cells.1 Its antioxidant properties are utilized in cardiovascular disease to inhibit LDL oxidation and diminish plaque formation associated with heart disease, and diminishes the risk of age-related macular degeneration and cataracts.1 It has proven beneficial effects in allergies, eczema, inflammation, lead toxicity, and healing connective tissue damage.
How much vitamin C does my child need?
The RDA for Vitamin C for children and adults is listed below. Remember that the Recommended Dietary Allowance is the average daily intake of a vitamin sufficient to prevent deficiency in 97-98% of the population. Some patients will need more to prevent deficiency. Individuals who regularly smoke require an additional 35 mg per day to combat the oxidative stress associated with chronic tobacco use.
- Birth – 6 months: 40 mg (Adequate intake)
- Infants 6 – 12 months: 50 mg (Adequate intake)
- Children 1 – 3 years: 15 mg
- Children 4 – 8 years: 25 mg
- Children 9 – 13 years: 45 mg
- Adolescent girls 14 – 18 years: 65 mg
- Adolescent boys 14 – 18 years: 75 mg
- Adult men (>19 years): 90 mg
- Adult women (>19 years): 75 mg
- Pregnancy: 100 mg
- Lactation: 120 mg
Infants and children with a vitamin C deficiency are usually given 100-300 mg per day for one month and/or until all signs and symptoms of deficiency subside.3 Symptoms such as spontaneous bleeding, gum swelling, and behavioral adaptations are the quickest to recover, while bone abnormalities may take more time.
Food sources of vitamin C
The richest source of vitamin C comes from a small berry called camu berry. Although fresh camu berries are difficult to come by, it’s typically carried in a powdered form at health food stores. The powder can be added to meals such as smoothies, yogurt, or oatmeal bowls.
Other sources of vitamin C include:
- brussel sprouts
Vitamin C is often one of the nutrients found in fortified foods like cereals, but ideally, most vitamin C would be obtained through whole food products. Vitamin C can be destroyed by light, heat, and oxidation. Eating some vitamin C rich foods raw and/or utilizing quick heating methods like blanching can help preserve the vitamin C content.
What form of vitamin C is used for supplementation?
Supplements typically supply vitamin C as ascorbic acid, calcium ascorbate, and/or sodium ascorbate.1 Vitamin C supplements can be irritating to the stomach and in that case, buffered vitamin C is also available.
What are the signs of vitamin C deficiency in children?
Vitamin C deficiency is rare in developed countries, but is known for having killed up to two million sailors between 1500 and 1800.2 A severe deficiency in vitamin C is called scurvy and can occur in as little as a month of inadequate intake, but generally takes several months to manifest.
The symptoms of scurvy occur on a spectrum and result from the loss of collagen related to inadequate vitamin C. Collagen is necessary for strengthening connective tissues and some of the symptoms include easily fractured bones, bone pain, easy bruising, and bleeding gums.1 Other symptoms include clogged and enlarged hair follicles resulting in corkscrew shaped hair, petechiae, splinter hemorrhages, decaying teeth, fatigue, and impaired wound healing.1 In severe cases, behavior changes and death may occur.
The symptoms of scurvy are sometimes referred to as the “four H’s”; hemorrhagic signs, hyperkeratosis of hair follicles, hypochondriasis, and hematologic abnormalities.1 Vitamin C is important for facilitating the absorption of iron, and thus a severe vitamin C deficiency may lead to iron deficiency anemia.2 In children, a vitamin C deficiency may present as rheumatologic disorders like arthritis, and swelling of the knees and ankles is a common telltale sign.
Older adults, smokers, alcoholics, drug users, and those with limited access to fruits and vegetables are at a greater risk of vitamin C deficiency. Children with Autism Spectrum Disorder, mental illness, sensory processing disorder, physical disabilities, or picky eating are at a greater risk of developing a vitamin C deficiency.3 Children with malabsorption disorders such as Inflammatory Bowel Disease or those adhering to a ketogenic diet for controlling epilepsy may also be at a greater risk.3 Children with certain types of cancer or end-stage renal disease are at an increased risk of deficiency due to the rapid turnover of vitamin C.3
It’s important to note that vitamin C deficiencies rarely occur in isolation. Children with vitamin C deficiency are more likely to have co-occurring deficiencies of vitamin B1, vitamin B6, vitamin B12, and vitamin D3. These should be considered when investigating a case of vitamin C deficiency.
Vitamin C and Nutrient interactions
Vitamin C interacts with several minerals. It enhances the absorption of both dietary iron and selenium, and is often encouraged as an addition to iron rich foods in those with iron deficiency anemia.4 For example, pairing a citrus like lemon with non-heme iron from dark leafy greens would maximize absorption. On the other hand, vitamin C can reduce the absorption of copper, nickel, and manganese since all four minerals share a transporter. If the transporter is full of vitamin C, there’s little room to pick up and transport the remaining three minerals. Excessively large doses of vitamin C may interfere with the absorption and metabolism of vitamin B12.
Is vitamin C safe in children?
The upper limit for vitamin C intake is 2000 mg/d.1 Over consuming vitamin C through whole foods is quite uncommon since absorption decreases when large amounts are consumed. Over supplementation is a greater risk and can become an issue since the intestines have limited ability to absorb vitamin C. The most common side effects of over supplementation are GI problems like diarrhea and abdominal pain.1 In rare instances, kidney stones can occur in people with a history of stones or renal dysfunction. Iron toxicity is a concern in those with disorders of iron metabolism such as hemochromatosis.1
What is “bowel tolerance?” of vitamin C?
Vitamin C supplementation is often dosed to “bowel tolerance”, meaning titrating the amount of oral vitamin C a patient tolerates without inducing diarrhea.5 The amount of vitamin C a person can tolerate usually increases in proportion to the severity of illness or the degree of stress the body is experiencing.
The method by which the dose is selected is a process of trial and error. First, a patient takes a daily dose of vitamin C at the upper limit (2,000 mg/day). This is dose-adjusted by weight for children. (E.g., a child may start with 500 mg per day). This dose is increased by 250 – 500 mg daily (50 – 125 mg daily for children) until loose stools occur. The last dose that did not cause loose stools is the patient’s daily recommended dose. Note that the patient may need to adjust their dose downward as vitamin levels are replenished.
Vitamin C Applications
The Common Cold
Vitamin C is often touted as a cure for the common cold, but there is a great deal of conflicting research surrounding its efficacy. A meta-analysis of 29 placebo-controlled trials found that regular vitamin C supplementation did not reduce the incidence of catching a cold in the general population However, it did reduce the risk in people under heavy physical stress such as soldiers and endurance athletes by nearly half.6 Regular vitamin C supplementation did reduce the duration of colds and the effect was greater in children than adults Vitamin C supplements taken after symptoms of a cold appear had little significant effect on the duration or severity on illness.6 Although, high doses (8 g/day), taken within the first 24 hours of cold symptom onset, and continued for at least 5 days has been shown to improve both symptoms and duration of illness.
In short, small doses of vitamin C taken after cold symptoms begin does little for the patient, but taking large, well-timed doses may reduce the duration and severity of the common cold. Regular vitamin C supplementation may be beneficial for people under a great deal of physical stress, but hasn’t proven effective at preventing the common cold in the general population.
Connective Tissue Support
Vitamin C plays a critical role in collagen synthesis and is essential for building and maintaining healthy connective tissue. For this reason, researchers have investigated the relationship between vitamin C supplementation and healing from bone, tendon, and ligament injuries. In a systematic review of 10 studies, researchers found that vitamin C accelerated bone healing after fracture, increased type 1 collagen synthesis, and reduced oxidative stress marker No adverse effects were reported in any of the studies. Low dose, oral administration of 60 mg/day of vitamin C appears to accelerate healing after musculoskeletal injuries.
One of the key drivers of allergies is oxidative stress. As discussed, vitamin C is a potent antioxidant that helps combat oxidative stress and return the body to homeostasis. Studies show that people with allergic diseases often have reduced plasma levels of vitamin C. In one observational study, intravenous high-dose (7.5 g/day) vitamin C significantly reduced respiratory or cutaneous allergy-related symptoms.
In a large study on children aged 6-12 years, those who consumed more vitamin C had fewer allergic rhinitis symptoms than children who consumed less vitamin C. Another study on children in Italy found that the regular consumption of vitamin C rich fruit was associated with a reduction in wheezing and other respiratory symptoms. There was a positive association with the amount of vitamin C rich fruit consumed and the reduction in respiratory symptoms associated with allergies and asthma.11
Note: It’s difficult to tease out the effect of just vitamin C, given the numerous beneficial compounds found in whole fruits. However, it is reasonable to conclude that an increase in vitamin C rich whole fruit consumption can reduce the severity of respiratory symptoms in children.
Although several studies show a correlation between serum vitamin C status and incidence of eczema, information regarding specific supplementation guidelines in children with eczema remains unclear. Vitamin C does help stimulate keratinocyte production, ultimately strengthening the epidermal barrier.12 It also acts as an antihistamine and reduces overall inflammation, which in theory, may reduce the risk and/or severity of eczema.
Lead Toxicity & Secondhand Smoke
Lead toxicity in children is unfortunately quite common in the United States, especially in urban areas. Children of women exposed to lead during pregnancy are more likely to have abnormal physical and/or cognitive development, while children chronically exposed to lead are more likely to have learning disabilities and behavioral problems.13 Studies have found that higher serum vitamin C concentrations are associated with significantly lower blood lead concentrations, although the mechanism of action remains unclear.13 Cigarette smoking and second-hand exposure to cigarette smoke is a common contributor of lead exposure. Vitamin C supplementation not only lowers blood lead concentration in the smoker, but can help reduce the risk of lead toxicity in children exposed to secondhand smoke.
There is a strong correlation between vitamin C status and inflammatory markers such as cytokines (IL-4, IL-18), interferon-y, tumor necrosis factor, and immunoglobulin E (Ig-E)14. Controlled studies are limited on the effect of vitamin C in inflammation in children, but studies have found that 500 mg, twice a day of vitamin C reduces hs-CRP, IL-6 and fasting blood glucose in diabetic adults, all of which are indicators of inflammation.17 Since specific supplementation for vitamin C in inflammatory conditions in children is unclear, emphasizing whole food sources of vitamin C is the best course of action.
Maternal Vitamin C Intake and Allergic Disease
A study investigating the relationship between antioxidant intake in pregnancy with the rates of wheezing and eczema in the child’s first two years of life found that vitamin C intake during pregnancy was positively associated with the incidence of wheezing and eczema in early childhood.15
Some studies indicate a correlation between vitamin C intake/serum concentrations in cardiovascular disease and several types of cancer, especially those of the oral cavity. There is also preliminary evidence suggesting a connection between vitamin C and autism symptoms. These topics either require more research to draw conclusions, or are beyond the scope of this article.
Vitamin C is an affordable and easy to administer supplement since it usually tastes good. The risk of adverse effects are limited, although diarrhea is relatively common. It may be used to support the immune system, reduce inflammation, expedite connective tissue repair, and more. Supplementation is quite safe, but whole food sources from vibrantly colored fruits and vegetables are preferable for everyday consumption. Specific supplementation can be considered under the supervision of a medical provider.
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- Gropper S, Smith J, Carr T. Advanced Nutrition and Human Metabolism: Seventh Addition. Cengage Learning. 2018:455-460.
- The Nutrition Source. Vitamin C. Harvard TH Chan School of Public Health. 2022.
- Agarwal A, Shaharyar A, Kumar A, Bhat MS, Mishra M. Scurvy in pediatric age group – A disease often forgotten?. J Clin Orthop Trauma. 2015;6(2):101-107. doi:10.1016/j.jcot.2014.12.003
- Solomons N, Viteri F. Biological Interaction of Ascorbic Acid and Mineral Nutrients. Advances in Chemistry. 1982;23:551-569.
- Cathcart RF. Vitamin C, titrating to bowel tolerance, anascorbemia, and acute induced scurvy. Med Hypotheses. 1981;7(11):1359-1376. doi:10.1016/0306-9877(81)90126-2
- Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013;2013(1):CD000980. Published 2013 Jan 31. doi:10.1002/14651858.CD000980.pub4
- Bucher A, White N. Vitamin C in the Prevention and Treatment of the Common Cold. Am J Lifestyle Med. 2016;10(3):181-183. Published 2016 Feb 9. doi:10.1177/1559827616629092
- DePhillipo NN, Aman ZS, Kennedy MI, Begley JP, Moatshe G, LaPrade RF. Efficacy of Vitamin C Supplementation on Collagen Synthesis and Oxidative Stress After Musculoskeletal Injuries: A Systematic Review. Orthop J Sports Med. 2018;6(10):2325967118804544. Published 2018 Oct 25. doi:10.1177/2325967118804544
- Vollbracht C, Raithel M, Krick B, Kraft K, Hagel AF. Intravenous vitamin C in the treatment of allergies: an interim subgroup analysis of a long-term observational study. J Int Med Res. 2018;46(9):3640-3655. doi:10.1177/0300060518777044
- Seo JH, Kwon SO, Lee SY, et al. Association of antioxidants with allergic rhinitis in children from seoul. Allergy Asthma Immunol Res. 2013;5(2):81-87. doi:10.4168/aair.2013.5.2.81
- Forastiere F, Pistelli R, Sestini P, et al. Consumption of fresh fruit rich in vitamin C and wheezing symptoms in children. SIDRIA Collaborative Group, Italy (Italian Studies on Respiratory Disorders in Children and the Environment). Thorax. 2000;55(4):283-288. doi:10.1136/thorax.55.4.283
- Wang K, Jiang H, Li W, Qiang M, Dong T, Li H. Role of Vitamin C in Skin Diseases. Front Physiol. 2018;9:819. Published 2018 Jul 4. doi:10.3389/fphys.2018.00819
- Higdon J. Vitamin C. Linus Pauling Institute. 2022.
- Kamel I, Sabry R, Hamid E, Aly H, Ahmed H. Inflammatory cytokines, vitamin C and E in children versus adolescents with atopic dermatitis. Journal of Pediatric Biochemistry 2014; 04(03): 145-151.
- Martindale S, McNeill G, Devereux G, Campbell D, Russell G, Seaton A. Antioxidant Intake in Pregnancy in Relation to Wheeze and Eczema in First Two Years of Life. American Journal of Respiratory and Critical Care Medicine. 2004;171:2.
- Dolske MC, Spollen J, McKay S, Lancashire E, Tolbert L. A preliminary trial of ascorbic acid as supplemental therapy for autism. Prog Neuropsychopharmacol Biol Psychiatry. 1993;17(5):765-774. doi:10.1016/0278-5846(93)90058-z