Vitamin C in health promotion: Emerging research and implications for new intake recommendations

Long before vitamin C was recognized as an essential nutrient, Dr. James Lind found that a component in citrus fruits could cure scurvy in British sailors, supporting England’s naval dominance and helping shape the world we live in today (1).  Years later, a hexuronic acid (now known as ascorbic acid) was identified as “vitamin C” and its important role in the biochemical mechanism of collagen formation was elucidated (2,3).  While this is the primary reason that vitamin C is considered an essential nutrient, recent research suggests that vitamin C may also be important for other chronic diseases.  In addition, the levels of intake required for optimal health may be higher than currently recommended.

Immune Function

Immune function is one of the most well-recognized benefits of vitamin C.  Vitamin C is preferentially taken up by circulating immune cells, resulting in levels 20-60 times those of surrounding cells (4).  This may protect neutrophils from the reactive oxygen species that are used to kill pathogenic bacteria or viruses.  Vitamin C also influences the movement of immune cells to sites of infection, and decreased vitamin C levels have been observed in individuals with infections (5).  A recent Cochrane meta-analysis of clinical trials of vitamin C supplementation in humans concluded that supplementation of 200 mg or more of vitamin C reduced the duration of common cold symptoms in both adults and children (6).

Non-Communicable Diseases

Vitamin C is also associated with certain non-communicable diseases such as cardiovascular disease, cancer and even Alzheimer’s disease.  Population studies have reported associations between vitamin C and decreased cardiovascular risk (7).  Several meta-analyses of clinical trials with vitamin C supplementation have reported improvements in endothelial function (8) and blood pressure (9).  Vitamin C intake has also been associated with decreased incidence of certain cancers (10–12) and Alzheimer’s disease (13,14), although cause and effect relationships are unclear.  Recently, there has been increased medical interest in the possible benefits of intravenous vitamin C to support quality of life in patients receiving chemotherapy (15).

In light of this recent evidence, some experts have advocated for increasing the daily recommended intake to 200 mg or more per day (16), an amount that can be obtained by consuming 5 servings of fruits and vegetables.  However, in many parts of the world, marginal or outright vitamin C deficiency is surprisingly common.  Marginal deficiency or depletion in vitamin C (<28 µmol/L) has been reported in 34-46 percent of a low-income UK population (17), and suboptimal vitamin C status (<53 µmol/L) has been reported in 46 percent of the U.S. population (18).

Clearly, vitamin C is important for more aspects of health beyond simply the prevention of scurvy.  Many individuals don’t consume the recommended amounts of fruits and vegetables, and many have vitamin C levels in the body that are below recommendations.  Considering the possible benefits, there is an opportunity to advocate for increased consumption of foods high in vitamin C or supplements that can help individuals reach the levels of vitamin C in the body that are associated with optimal health.

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REFERENCES

1. Lind J. Treatise of the Scurvy in Three Parts [Internet]. Edinburgh: Sands, Murray and Cochran; 1753 [cited 2017 Dec 13]. 22 p. Available from: http://www.jameslindlibrary.org/lind-j-1753/
2. Svirbely JL, Szent-Györgyi A. Hexuronic Acid as the Antiscorbutic Factor. Nature. 1932;129:576.
3. Englard S, Seifter S. The Biochemical Functions of Ascorbic Acid. Annu Rev Nutr. 1986;6:365–406.
4. Carr AC, Maggini S. Vitamin C and Immune Function. Nutrients. 2017;9:1211.
5. Bakaev VV, Duntau AP. Ascorbic acid in blood serum of patients with pulmonary tuberculosis and pneumonia. Int J Tuberc Lung Dis. 2004;8:263–6.
6. Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews [Internet]. John Wiley & Sons, Ltd; 2013 [cited 2016 Jun 16]. Available from: http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD000980.pub4/abstract
7. Moser MA, Chun OK. Vitamin C and Heart Health: A Review Based on Findings from Epidemiologic Studies. Int J Mol Sci. 2016;17:1328.
8. Ashor AW, Lara J, Mathers JC, Siervo M. Effect of vitamin C on endothelial function in health and disease: A systematic review and meta-analysis of randomised controlled trials. Atherosclerosis. 2014;235:9–20.
9. Juraschek SP, Guallar E, Appel LJ, Miller ER. Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 2012;95:1079–88.
10. Finck H, Hart AR, Lentjes MA, Jennings A, Luben RN, Khaw K-T, Welch AA. Cross-sectional and prospective associations between dietary and plasma vitamin C, heel bone ultrasound, and fracture risk in men and women in the European Prospective Investigation into Cancer in Norfolk cohort. Am J Clin Nutr. 2015;102:1416–24.
11. Cao D, Shen K, Li Z, Xu Y, Wu D. Association between vitamin C Intake and the risk of cervical neoplasia: A meta-analysis. Nutr Cancer. 2016;68:48–57.
12. Hua Y-F, Wang G-Q, Jiang W, Huang J, Chen G-C, Lu C-D. Vitamin C Intake and Pancreatic Cancer Risk: A Meta-Analysis of Published Case-Control and Cohort Studies. PLOS ONE. 2016;11:e0148816.
13. Silva SL da, Vellas B, Elemans S, Luchsinger J, Kamphuis P, Yaffe K, Sijben J, Groenendijk M, Stijnen T. Plasma nutrient status of patients with Alzheimer’s disease: Systematic review and meta-analysis. Alzheimers Dement J Alzheimers Assoc. 2014;10:485–502.
14. Li F-J, Shen L, Ji H-F. Dietary intakes of vitamin E, vitamin C, and β-carotene and risk of Alzheimer’s disease: a meta-analysis. J Alzheimers Dis JAD. 2012;31:253–8.
15. Carr AC, Vissers MCM, Cook JS. The Effect of Intravenous Vitamin C on Cancer- and Chemotherapy-Related Fatigue and Quality of Life. Front Oncol [Internet]. 2014 [cited 2017 May 26];4. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4199254/
16. Frei B, Birlouez-Aragon I, Lykkesfeldt J. Authors’ Perspective: What is the Optimum Intake of Vitamin C in Humans? Crit Rev Food Sci Nutr. 2012;52:815–29.
17. Mosdøl A, Erens B, Brunner EJ. Estimated prevalence and predictors of vitamin C deficiency within UK’s low-income population. J Public Health. 2008;30:456–60.
18. Dionne CE, Laurin D, Desrosiers T, Abdous B, Sage NL, Frenette J, Mondor M, Pelletier S. Serum vitamin C and spinal pain: a nationwide study. Pain. 2016;157:2527–35.