Vitamin C And Cataracts: Too Much Of A Good Thing?
Posted on 30. Nov, 2009 by Kerry D Friesen, M.D. in Aesthetics & Anti•Aging, Brain Health, Men's Health, Women's Health
Cataract Surgery: A Last Resort
The Two Faces Of Vitamin C
L-ascorbic acid or “vitamin C” is an essential nutrient and potent anti-oxidant.
Vitamin C has a long history dating back to 1795 when the British Navy introduced lime juice to prevent the scourge of scurvy.
More recently, mega-doses of vitamin C have been used for everything from the common cold to cancer.
While generally recognized as safe, experimental animal studies have suggested a link between high-dose vitamin C ( > 1000 mgs/day ) and age-related cataracts.
A cataract is a cloudy area in the otherwise crystal-clear lens of the eye. Smoking, diabetes, UV radiation, cortisone, trauma and inflammatory diseases, all accelerate cataract formation.
As a potent anti-oxidant, vitamin C would ordinarily be expected to counter-act the cellular “oxidative-stress” associated with the medical disorders mentioned. Now a recent study of 24,593 Swedish women aged between 49 and 83, conducted over a eight-year period, suggests vitamin C may have a more sinister side.
Information about vitamin C supplementation, cortisone, hormone-replacement therapy and other lifestyle factors was collected from 1997 to 2005.
More than 2,400 cataract surgeries were performed on the study participants over the same eight-year period.
Conclusion?
Among women over 65 who consistently took greater than 1000 milligrams of vitamin C per day, the risk of cataract formation increased by 38%.
For women on hormone-replacement therapy, the risk increased by 56%.
According to the researchers the “results indicate that the use of vitamin C supplements may be associated with higher risk of age-related cataract among women.”
What To Do?
If you are currently taking more than 1000 milligrams of vitamin C per day and fall into one of the above higher risk categories, start by reducing your daily intake to only 500 milligrams per day. Although there are anecdotal reports of “rebound scurvy”, no scientific proof for this supposed condition exists.
Aim for 250 milligrams of vitamin C per day and consider taking a different anti-oxidant. Polyphenols or plant phytochemicals are extremely effective antioxidants and have not been shown to increase oxidative-stress or function as “pro”-oxidants.
Moreover, do not smoke, wear UV-blocking sunglasses and avoid cortisone therapy if you can. If you are a diabetic, adopt the Mediterranean diet and exercise more for better blood-sugar control.
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi:10.3945/ajcn.2009.28528
“Vitamin C supplements and the risk of age-related cataract: a population-based prospective cohort study in women”
Authors: S. Rautiainen, B. Ejdervik Lindblad, R. Morgenstern, A. Wolk
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