The Antioxidant Functions of Riboflavin
When we think of antioxidant nutrients, we think of the big names: vitamin C, vitamin E, the carotenoids, selenium. It is less well known that riboflavin also supports the body’s antioxidant functions. These less well known properties have been reviewed recently by Ashoor and Saedisomeolia.
Riboflavin is also commonly known as vitamin B2 and as it is a B-vitamin, is water-soluble. The main role of riboflavin is to help with the conversion of carbohydrates to energy in the body. It also helps to convert vitamin B6 and folate to their active forms.
The main antioxidant activity of riboflavin arises from its involvement in the conversion of glutathione. Glutathione is a very important antioxidant in the body that it is only effective when in the reduced form. Riboflavin and the glutathione reductase enzyme are both used to convert oxidized glutathione to the reduced form. When riboflavin levels are low, the activity of the glutathione reductase the body actually increases the activity of the glutathione reductase enzyme in an attempt to help convert sufficient glutathione to the reduced form. This is also the basis of the test for functional riboflavin deficiency, the erythrocyte glutathione reductase activity test.
Riboflavin also affects levels of other antioxidant enzymes, including superoxide dismutase, catalase and glutathione peroxidase. Some studies have found that either riboflavin deficiency, or supplementation with riboflavin, affect levels of these antioxidant enzymes. For other research papers, the relationship has been unclear. It is possible that differing levels of underlying oxidative stress, and the extent of deficiency, affect the relationship. For example, in mild deficiency, the activity of the enzymes may be enhanced to provide additional antioxidant capacity, and it is only with stark deficiency that supplementation is beneficial, or the activity of antioxidant enzymes is compromised.
Although intakes are generally adequate in developed countries (see www.micronutrientcalculator.org for data from the US population), researchers (such as Hoey, McNulty and Strain) caution that the majority of people living in developing countries may be deficient in riboflavin. The non-specific nature of riboflavin deficiency symptoms means that there is little impetus to address riboflavin deficiency over other deficiency diseases that have a larger impact on health and productivity.
The current review also shows that the functions of riboflavin extend beyond carbohydrate metabolism to affect antioxidant status. This could be relevant for chronic disease prevention.
Marziyeh Ashoori and Ahmad Saedisomeolia. Riboflavin (vitamin B2) and oxidative stress: a review . British Journal of Nutrition, available on CJO2014. doi:10.1017/S0007114514000178.
Hoey L, McNulty H, Strain JJ. Studies of biomarker responses to intervention with riboflavin: a systematic review. Am J Clin Nutr. 2009 Jun;89(6):1960S-1980S. doi: 10.3945/ajcn.2009.27230B. Epub 2009 Apr 29. http://www.ncbi.nlm.nih.gov/pubmed/19403631
Hyman, M. Glutathione: The Mother of All Antioxidants. Huffington Post. 04/10/2010. http://www.huffingtonpost.com/dr-mark-hyman/glutathione-the-mother-of_b_530494.html
Northrop-Clewes CA, Thurnham DI. The discovery and characterization of riboflavin. Ann Nutr Metab. 2012;61(3):224-30. doi: 10.1159/000343111. Epub 2012 Nov 26. http://www.ncbi.nlm.nih.gov/pubmed/23183293