The coronavirus COVID-19 pandemic is the defining global health crisis of our time and since we have seen many associations of vitamin C with the notorious virus. Our country is facing a much tougher challenge in curbing the COVID-19 pandemic in the third wave compared to the previous ones. You can read more about other evidence-based ingredients that regulate and strengthen our body’s defence system here. In this article, we will focus on the discussion of vitamin C.
Vitamin C is a water-soluble nutrient with many important functions in your body by acting as a potent antioxidant that stabilizes free radicals and prevent cellular damage. It is also known as L-ascorbic acid, or simply ascorbic acid. Contrary to fat-soluble vitamins, water-soluble vitamins do not get deposited within the body. Instead, the vitamin C that you ingest gets distributed to your tissues via body fluids, and any extra gets eliminated in urine. Now you may ask, since we do not have the ability to store vitamin C and any extra gets excreted out from our body system, why do we need to take vitamin C supplements?
Unable to Synthesize Vitamin C
Unlike other animals, humans cannot produce vitamin C on our own endogenously. Humans and certain other vertebrates are deprived of the enzyme L-glucono-gamma lactone oxidase mandatory for in vivo synthesis of vitamin C.1 Therefore, you must get sufficient levels of vitamin C from supplements to maintain good health.
The More the Merrier?
Oral consumption of vitamin C results in tissue and plasma concentrations that the body tightly controls. At doses above 1 g per day, absorption falls to less than 50% and absorbed, unused ascorbic acid is excreted in the urine. Results from pharmacokinetic studies reveal that oral doses of 1.25 g per day ascorbic acid yield mean peak plasma concentrations of 135 micromol/L, which are about two times higher than those produced by consuming 200–300 mg per day from vitamin C-rich foods.2 The total body content of vitamin C ranges from 300 mg (at near vitamin C deficiency or seen as scurvy) to about 2 g.3
Health Benefit 1: Boosts Immune System
One of the most common reasons people consume vitamin C supplements is the understanding that they help prevent the common cold. A 2007 Cochrane review looked at placebo-controlled trials involving the use of at least 200 mg per day vitamin C ingested either continuously as a prophylactic treatment or after the onset of cold symptoms.4 Preventive use of vitamin C in doses ranging from 250 mg per day to 1 g per day reduced cold incidence by 50%.4 In the general population, use of prophylactic vitamin C moderately lowered cold duration by 8% in adults and 14% in children.4 Overall, the evidence to date suggests that regular intakes of vitamin C at doses of at least 200 mg per day shortens the duration of the common cold and ameliorates symptom severity.
Health Benefit 2: Stimulates Collagen Synthesis
Many has heard that vitamin C improves the skin complexion, but not many digs into details to find out how it helps to enhance one’s skin conditions. Vitamin C acts as a co-factor for the proline and lysine hydroxylases that stabilise the collagen molecule tertiary structure, and it also promotes collagen gene expression by stimulating collagen mRNA production by fibroblasts.5 In other words, vitamin C promotes collagen cross-linking and synthesis, in turn reducing wrinkles formation.6 Read more about collagen here.
Health Benefit 3: Inhibits Melanogenesis
Melanogenesis is the process whereby the undesired pigment melanin is produced in melanosomes by melanocyte cells. Vitamin C derivatives, including the magnesium phosphate ascorbyl derivative, have been illustrated to minimise melanin synthesis, owing to its ability to hinder the action of tyrosinase, the rate-limiting enzyme in melanogenesis.5
Health Benefit 4: Helps Absorb Iron
Vitamin C has been proven to be a powerful enhancer of iron absorption. It captures non-heme iron by forming a chelate at acidic pH that remains soluble at the alkaline pH of the duodenum and stores it in a form that’s more easily absorbed by your body.7,8 Iron absorption is evidently shown to be higher by 67% by taking 100mg vitamin C with a complete meal.9
Groups at Risk of Inadequacy
We now understand that our bodies cannot produce vitamin C and that we need to obtain this nutrient from the intake of food or supplements. Do we all have the same requirement of vitamin C? Are there certain groups of people that need more? The following groups are more likely than others to be at risk of obtaining insufficient levels of vitamin C; the smokers or passive smokers (high oxidative stress results in higher requirement10), individuals with limited food variety or picky eater, individuals with malabsorption (impaired intestinal absorption leads to lower plasma concentration) or end stage kidney failure on haemodialysis (higher excretion rate).
Health Risk from Excessive Vitamin C
We have covered on the health benefits from supplementing with vitamin C products, but is there no harm at all in excessively consuming vitamin C? The most common side effect of high vitamin C intake is digestive distress. You’re most likely to suffer from digestive symptoms including diarrhoea and nausea if you consume more than 2000 mg of vitamin C at once. Thus, a tolerable upper limit of 2000 mg per day has been established.11,12
Due to its function as an antioxidant and its role in immune function, vitamin C has been promoted as a means to help prevent and/or treat numerous health conditions. Since your body does not store vitamin C nor produce it on its own, it is important to ensure adequate daily vitamin C intake, and the easiest way is to consume 1000 mg of vitamin C as the dosage is high enough to exhibit health benefits and not excessive to cause health risk.
- Telang PS. Vitamin C in dermatology. Indian Dermatol Online J. Apr-Jun 2013;4(2):143-146.
- Padayatty SJ, Sun H, Wang Y, Riordan HD, Hewitt SM, Katz A, Wesley RA, Levine M. Vitamin C pharmacokinetics: implications for oral and intravenous use. Ann Intern Med 2004; 140:533-537.
- Jacob RA, Sotoudeh G. Vitamin C function and status in chronic disease. Nutr Clin Care 2002;5:66-74.
- Douglas RM, Hemilä H, Chalker E, Treacy B. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev 2007;(3):CD000980.
- Pullar JM, Carr AC, Vissers MCM. The roles of Vitamin C in skin health. Nutrients. 2017;9(866):1-27.
- Wang K, Jiang H, Li W, Qiang M, Dong T, Li H. Role of Vitamin C in skin diseases. Frontiers in Physiology. July 2018;9(819):1-9.
- Lynch SR, Cook JD. Interaction of vitamin C and iron. Ann N Y Acad Sci. 1980;355:32-44.
- Hurrell R, Egli I. Iron bioavailability and dietary reference values. Am J Clin Nutr. 2010 May;91(5):1461S-1467S.
- Hallberg L, Hulthen L. Prediction of dietary iron absorption: an algorithm for calculating absorption and bioavailability of dietary iron. Am J Clin Nutr. 2000 May;71(5):1147-60.
- Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoidsexternal link disclaimer. Washington, DC: National Academy Press, 2000.
- Hathcock JN, Azzi A, Blumberg J, Bray T, Dickinson A, Frei B, Jialal I, Johnston CS, Kelly FJ, Kraemer K, Packer L, Parthasarathy S, Sies H, Traber MG. Vitamins E and C are safe across a broad range of intakes. Am J Clin Nutr. 2005 Apr;81(4):736-45.
- Sestili MA. Possible adverse health effects of vitamin C and ascorbic acid. Semin Oncol. 1983 Sep;10(3):299-304.