Antioxidants and polyphenols are plant-based nutrients that protect the brain. The older you are the more your brain needs to disarm harmful oxidants, the toxic by-products of the brain’s energy creation, and to reduce inflammation. Smoking and long-term exposure to polluted air are significant risk factors for Alzheimer’s disease.
The more fruit and vegetables a person eats the lower is their risk of cognitive decline, with vegetables being particularly protective. The best kinds of vegetables are carrots, cauliflower, broccoli, Brussels sprouts, cabbage, spinach and mushrooms. The best fruits are berries, especially blueberries and strawberries. Polyphenols, found not only in fruit and vegetables, but also in tea, especially green tea, red grapes and the cacao in dark chocolate, are associated with preserving memory and a number of mechanisms exist to explain their positive actions on cognitive performance. Olive oil is also promising in this regard. Six servings (500g) a day of fruit and vegetables has been observed to reduce risk of cognitive decline and dementia. A further study indicated that 10 servings (overall 800g) may help to reduce the risk of all cause mortality, although this study did not consider dementia specifically and this area would benefit from further research. Those in the top fifth of consumption of these foods and drinks high in antioxidants and polyphenols have half the risk of dementia. A randomised controlled trial found cognitive improvement with a Mediterranean style diet with extra virgin olive oil or nuts.
A number of key vitamins, as measured in food and in the blood, correlate with decreased risk. These include vitamin C, both in food and supplements, and vitamin E in supplements. In a population study it was found that those taking supplements of both vitamin C (1g) and vitamin E substantially reduced risk of developing Alzheimer’s disease compared with those not taking these two supplements; either supplement on its own was not protective. Vitamin E was found to be beneficial in mild to moderate AD by slowing decline of cognition. N-acetyl cysteine, the precursor of glutathione, Co-enzymeQ10 and resveratrol, found in red grapes, is also neuroprotective.
These nutrients, together with anthocyanidins in blue/red foods and beta-carotene in orange foods are team players in disarming harmful oxidants that age the brain, however they also have roles when acted on by the gut microbiome producing secondary metabolites involved in liver function, detoxification and cell signalling with anti-inflammatory effects supporting brain function, as well as reducing cardiovascular risk and hence supply of nutrients and oxygen to the brain.
Practical Steps for Reducing Risk of Cognitive Decline
In practical terms this means: