Do natural antioxidants play a role in Alzheimer’s disease?
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by globally impaired cognitive functions. Oxidative stress is involved in the formation of plaques and tangles, which damage neuronal cells in AD. Treatments retarding the progression of AD or significantly improving cognition are not available. Diet has been recognized as a modifiable lifestyle factor capable of affecting the risk of developing AD, since it may influence inflammation and oxidative stress in the brain. Dietary intake of natural antioxidants, such as polyphenols, carotenoids and vitamins C and E, is thought to reduce oxidative stress and to have preventive or therapeutic potential in AD. Several antioxidants have shown promise in animal models of AD. However, there is no evidence of clinical efficacy of natural antioxidants in people with AD. The use of antioxidants may be hindered by their limited bioavailability. Furthermore, antioxidants administered in high concentrations could have detrimental effects due to their capacity to act as prooxidants. Potential effects of natural antioxidants in the prevention of AD should be assessed in studies with long-term exposure to compounds with high bioavailability. In addition, the assessment of the effectiveness of antioxidant-rich diets in AD deserves further investigation.