Oxidative stress, antioxidants and diabetes

What is the relationship between oxidative stress and antioxidant defenses in the body, and diabetes?


The human body runs on fuel, like the petrol in your car. Glucose and oxygen are chiefly used to fuel chemical reactions inside the body. This is known as metabolism.

Metabolism provides the vital energy for every cell to do what needs to be done. During normal metabolism, a small proportion of oxygen is converted into toxic by-products collectively known as Reactive Oxygen Species (or free radicals). When free radicals attack the molecular components that make up the body, they don’t work as they should.

This can lead to a number of health problems, one of which is diabetes.

Antioxidant defenses

Each cell and each tissue has its own antioxidant defense systems to remove free radicals before they can do any damage.

In people with diabetes, the production of free radicals increases, while the effectiveness of their antioxidant defenses declines. If the production of free radicals outstrips antioxidant defense mechanisms, a state of oxidative stress is said to exist.

Oxidative stress

As there is a strong association between oxidative stress and diabetes, and people with diabetes often have low levels of antioxidants in their blood, it makes sense to target free radicals as a means to prevent diabetes and its complications.

Consequently, antioxidants are the most widely used complementary therapy for preventing and treating diabetes. However, research is yet to establish whether any of them can significantly improve health outcomes.

Should we consume antioxidants?

The problem is that although the idea of taking antioxidants is logical, long-term clinical trials with antioxidant supplements have not shown any clear advantages for the prevention of diabetes or other diseases.

Indeed, the net effects of some common antioxidants, including beta-carotene, vitamin A, vitamin E and folate, may be harmful in some settings, especially when you take excessive doses.

Diets naturally rich in antioxidants are associated with lower rates of diabetes, but whether it is the antioxidants, or other components of the diet and/or its processing, that causes this remains to be seen.

Certainly, though, the benefits of eating a juicy orange appear to extend well beyond its vitamin C content.


  • Bibiana Garcia-Bailo, Ahmed El-Sohemy, Pierre S Haddad, Paul Arora, Firas BenZaied, Mohamed Karmali & Alaa Badawi. (2011). Vitamins D, C, and E in the prevention of type 2 diabetes mellitus: modulation of inflammation and oxidative stress. Biologics: Targets & Therapy. Jan 19. Available here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3044790/
  • Jeanette Schultz Johansen, Alex K Harris, David J Rychly, and Adviye Ergul (2005). Oxidative stress and the use of antioxidants in diabetes: Linking basic science to clinical practice. Cardiovasc Diabetol. 2005; 4: 5. Available here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1131912/
  • Zunino SJ, Storms DH, Stephensen CB. (2007). Diets rich in polyphenols and vitamin A inhibit the development of type I autoimmune diabetes in nonobese diabetic mice.J Nutr. 2007 May;137(5):1216-21. Available here: http://jn.nutrition.org/content/137/5/1216.long
  • Harding AH, Wareham NJ, Bingham SA, Khaw K, Luben R, Welch A, Forouhi NG. (2008). Plasma vitamin C level, fruit and vegetable consumption, and the risk of new-onset type 2 diabetes mellitus: the European prospective investigation of cancer–Norfolk prospective study.Arch Intern Med. Jul 28;168(14):1493-9.

Last reviewed 15/May/2017


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