Exploring the actions of vitamin C
==================================

* Undurti N. Das

Vitamin C is an antioxidant with significant physiologic actions. For instance, it has been reported to lower erythrocyte sorbitol concentrations, which may make it useful in treating diabetes.1 Data from the 3rd National Health and Nutrition Examination Survey showed that mean serum vitamin C concentrations were significantly lower in people with newly diagnosed diabetes than in people who did not have diabetes,2 lending support to the earlier belief that diabetes mellitus may be associated with decreased serum vitamin C concentrations. These results support the contention of Sebastian Padayatty and Mark Levine that subclinical vitamin C deficiency is more common than is generally recognized.3 An inverse association has been reported between plasma vitamin C concentration and glycosylated hemoglobin,4 suggesting that measures to increase plasma vitamin C levels may help to reduce the prevalence of diabetes. A colleague and I reported that 1500 mg of vitamin C, when given orally, reduces plasma glucose levels in patients with type 2 diabetes.5

Other studies have suggested that vitamin C reduces blood pressure.6,7 It may augment prostaglandin F and nitric oxide synthesis,8,9 which could account for its beneficial actions in diabetes and hypertension. The interactions of vitamin C with eicosanoids, nitric oxide, platelets, leukocytes and endothelial cells, among other types of molecules and cells, may account for some of its hitherto-unexplained beneficial actions. As suggested by Padayatty and Levine, more studies should be conducted on vitamin C's actions in various tissues, including cancerous ones.3 Until further studies are completed, however, caution should be exercised in advocating its use as an anticancer compound.

## References

1.  1. Vincent TE, Mendiratta S, May JM. Inhibition of aldose reductase in human erythrocytes by vitamin C. Diabetes Res Clin Pract 1999;43:1-8.
    
    [CrossRef](http://www.cmaj.ca/lookup/external-ref?access_num=10.1016/S0168-8227(98)00119-3&link_type=DOI) 
    
    [PubMed](http://www.cmaj.ca/lookup/external-ref?access_num=10199583&link_type=MED&atom=%2Fcmaj%2F165%2F1%2F13.4.atom) 

2.  2. Will JC, Ford ES, Bowman BA. Serum vitamin C concentrations and diabetes: findings from the Third National Health and Nutrition Examination Survey, 1988-1994. Am J Clin Nutr 1999;70:49-52.
    
    [Abstract/FREE Full Text](http://www.cmaj.ca/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6NDoiYWpjbiI7czo1OiJyZXNpZCI7czo3OiI3MC8xLzQ5IjtzOjQ6ImF0b20iO3M6MjE6Ii9jbWFqLzE2NS8xLzEzLjQuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9) 

3.  3. Padayatty SJ, Levine M. New insights into the physiology and pharmacology of vitamin C [editorial]. CMAJ 2001;164(3):353-5.
    
    [FREE Full Text](http://www.cmaj.ca/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiRlVMTCI7czoxMToiam91cm5hbENvZGUiO3M6NDoiY21haiI7czo1OiJyZXNpZCI7czo5OiIxNjQvMy8zNTMiO3M6NDoiYXRvbSI7czoyMToiL2NtYWovMTY1LzEvMTMuNC5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=) 

4.  4. Sargeant LA, Wareham NJ, Bingham S, Day NE, Luben RN, Oakes S, et al. Vitamin C and hyperglycemia in the European Prospective Investigation into Cancer — Norfolk (EPIC-Norfolk) study: a population-based study. Diabetes Care 2000;23:726-32.
    
    [Abstract/FREE Full Text](http://www.cmaj.ca/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6NzoiZGlhY2FyZSI7czo1OiJyZXNpZCI7czo4OiIyMy82LzcyNiI7czo0OiJhdG9tIjtzOjIxOiIvY21hai8xNjUvMS8xMy40LmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ==) 

5.  5. Sandhya P and Das UN. Vitamin C therapy for maturity onset diabetes mellitus: relevance to prostaglandin involvement. IRCS J Med Sci 1981;9:618.
    
    

6.  6. Duffy SJ, Gokce N, Holbrook M, Huang A, Frei B, Keaney JF Jr, et al. Treatment of hypertension with ascorbic acid. Lancet 1999;354:2048-9.
    
    [CrossRef](http://www.cmaj.ca/lookup/external-ref?access_num=10.1016/S0140-6736(99)04410-4&link_type=DOI) 
    
    [PubMed](http://www.cmaj.ca/lookup/external-ref?access_num=10636373&link_type=MED&atom=%2Fcmaj%2F165%2F1%2F13.4.atom) 
    
    [Web of Science](http://www.cmaj.ca/lookup/external-ref?access_num=000084183300016&link_type=ISI) 

7.  7. Block G, Mangels AR, Norkus EP, Patterson BH, Levander OA, Taylor PR. Ascorbic acid status and subsequent diastolic and systolic blood pressure. Hypertension 2001;37:261-7.
    
    [Abstract/FREE Full Text](http://www.cmaj.ca/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTU6Imh5cGVydGVuc2lvbmFoYSI7czo1OiJyZXNpZCI7czo4OiIzNy8yLzI2MSI7czo0OiJhdG9tIjtzOjIxOiIvY21hai8xNjUvMS8xMy40LmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ==) 

8.  8. Das UN. Hypertension and ascorbic acid. Lancet 2000;355:1273.
    
    [CrossRef](http://www.cmaj.ca/lookup/external-ref?access_num=10.1016/S0140-6736(05)74701-2&link_type=DOI) 
    
    [PubMed](http://www.cmaj.ca/lookup/external-ref?access_num=10770325&link_type=MED&atom=%2Fcmaj%2F165%2F1%2F13.4.atom) 

9.  9. Frei B. On the role of vitamin C and other antioxidants in atherogenesis and vascular dysfunction. Proc Soc Exp Biol Med 1999;222:196-204.
    
    [Abstract/FREE Full Text](http://www.cmaj.ca/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6NToic3BlYm0iO3M6NToicmVzaWQiO3M6OToiMjIyLzMvMTk2IjtzOjQ6ImF0b20iO3M6MjE6Ii9jbWFqLzE2NS8xLzEzLjQuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9)