Monday May 4, 2015 (foodconsumer.org) -- A new study suggests that taking vitamin C supplements may protect against Alzheimer's disease as the most commonly used antioxidant vitamin C, also known as ascorbic acid, was found inversely associated with the carotid intima–media thickness, which is an indicator for Alzheimer's disease or cognitive function.

The vascular health condition, which is known to be affected by antioxidants in the blood, is now believed to play a role in the pathology of Alzheimer's disease.  The study was meant to associate the circulating concentrations of various antioxidants with the carotid intima-media thickness (c-IMT)of older people with no or very mild cognitive impairment.

Plasma antioxidants measured for the study included vitamin A, C, E, uric acid and antioxidant enzymes superoxide dismutase and glutathione peroxidase.  Researchers found vitamins C and E were significantly lower in subjects with greater IMT.  This could mean that high vitamin C and E could prevent vascular damage.

However, vitamin C was the only antioxidant that has a dose-responsive effect on the IMT. Specifically, compared to those in the lowest quartile of vitamin C, people in the higher quartiles of vitamin C (from the second quartile to fourth quartile) had significantly decreased IMT, independent of confounders. 

The study concluded that "vitamin C plasma levels appear to be selectively associated with the risk of increasing C-IMT. An adequate vitamin C status might be particularly important for protection against AD (Alzheimer's disease) and other clinical manifestations of vascular and cognitive ageing."

Antioxidants are important for the protection against vascular damage.   Oxidized cholesterol is known to play a role in the vascular aging process.  Oxidation of cholesterol can be reduced by maintaining high plasma levels of antioxidant vitamins like vitamin C. (David Liu)

Reference

M. C. Polidori, C. Ruggiero, M. F. Croce, T. Raichi, F. Mangialasche, R. Cecchetti, L. Pelini, L. Paolacci, S. Ercolani, P. Mecocci  Association of increased carotid intima–media thickness and lower plasma levels of vitamin C and vitamin E in old age subjects: implications for Alzheimer’s disease, Journal of Neural Transmission, April 2015, Volume 122, Issue 4, pp 523-530