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From Chippenham, Wiltshire, England, United Kingdom:

On two occasions the by-product of 'Free Radicals' and the accepted statement that they cause damage to the eyes has been cited as a reason for individuals with diabetes NOT to undertake strenuous exercise. Therefore:

  1. Are 'Free Radicals' or any chemicals created by strenuous exercise likely to damage the eyes of those with diabetes?

  2. If yes are there guidelines about the limitations upon exercise that need to be observed, for example 50% max heart rate for an hour, not more than 2 hours sequentially, no more than 5 hours in 7 days etc?

  3. If yes is the effect accumulative, i.e. toxins not cleared from body?

I ask on my own behalf but also because I actively promote competitive cycling to those with diabetes. If competitive cycling/exercise is likely to damage to participants eyes I need to be aware of that fact and either cease, adapt or give an appropriate warning.

Your advice/opinion would be appreciated.


I am aware of no rigorous scientific evidence supporting the contention that exercise-induced free radicals contribute to diabetic eye disease. To the extent exercise improves blood glucose, blood pressure and blood lipid profiles, it will ameliorate diabetic microvasculopathy, including eye disease. Free radical damage may, in fact, play a role in the pathogenesis of many eye diseases (there is strong evidence for cataract, macular degeneration and diabetic retinopathy); in the case of diabetes specifically, however, the consensus view is that free radical oxidative damage occurs primarily as a result of hyperglycemia. My personal view is that optimizing blood glucose control in tandem with supplementary intake of targeted antioxidants is the wisest strategy.

Most cautionary statements regarding exercise in diabetes vis a vis eye disease are based on either (1) the fact that acute elevations in blood pressure may worsen pre-existing diabetic retinopathy or (2) that vitreous gelatin traction increases the risk of retinal detachment in those with pre-existing proliferative diabetic retinopathy.

The fundamental point is for patients to be aware of their retinal status. See the handout about this very topic from a talk I recently delivered to the Diabetes Exercise and Sports Association (


Original posting 20 Nov 2004
Posted to Exercise and Sports


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