The health of our brains also depends on what we eat. In fact, more and more scientific evidence shows that a diet rich in polyphenols is able to improve cognitive function and prevent its decline. A very recent review has collected the results of previous studies to allow us to understand the beneficial action on the brain of the main polyphenols and what are the foods not to be missed to keep neurodegenerations at bay. The research was published in the Nutrients journal by an Italian team from the University of Catania (Caruso et al, Nutrients, 2022).
The neuroprotective action of polyphenols
Polyphenols are a large group of substances with an antioxidant action that include a wide range of subfamilies. For example, there are flavonoids, such as the anthocyanins of berries or the isoflavones of soy, much studied by science, which has been able to demonstrate their neuropotective action, even for preventive purposes.
Then there are stilbenes, such as resveratrol from grapes, oleuropein from extra virgin olive oil, or curcumin from turmeric, also with a known neuroprotective action.
Then there are phenolic acids, contained in foods that are commonly brought to the table but which, compared to other members of the polyphenol family, have been less studied regarding their neuroprotective action. The review therefore also focused on phenolic acids, let's see what emerged.
Caffeic acid is a phenolic acid found in coffee, tea, but also in some fruits such as blueberries, kiwis, plums, cherries and apples. Studies have made it possible to observe that caffeic acid is neuroprotective thanks to its ability to counteract oxidative stress and neuroinflammation. Not only that, caffeic acid has been shown to improve memory and cognitive function, to counteract the accumulation of beta amyloid proteins, which together with inflammation are the hallmark of Alzheimer's disease, to support brain plasticity and increase the synthesis of synaptic proteins that, in neurons, are involved in the process of neurotransmitter exchange.
Among the phenolic acids, another neuroprotective substance is chlorogenic acid. This substance is found in apples, artichokes, carrots, eggplants, grapes, kiwis, plums, tea and coffee. Chlorogenic acid is anti-inflammatory and antioxidant and is able to increase the survival of neurons.
Ferulic acid is found in whole grains and in some fruits, such as blueberries and blackberries. Ferulic acid shows a powerful anti-inflammatory and antioxidant action, which helps protect against neurodegeneration. Not only that, ferulic acid helps improve mood and counteract depression, given its action on serotonin levels.
Do not forget rosmarinic acid, contained in various aromatic plants such as rosemary, marjoram, sage, thyme, oregano, basil, mint, lavender and lemon balm. The neuroprotective action of rosmarinic acid is traced back to its ability to regulate the activity of the transcription factor Nrf2, activating it and protecting it from free radical damage. Indeed, a decline in Nrf2 values was observed in cases of overt Alzheimer's disease.
Synapic acid, found in berries, but also in whole grains and oil seeds, is also very interesting. In fact, laboratory studies have made it possible to observe that synapic acid protected neuronal cells from death following exposure to accumulations of beta amyloid protein aggregates, as occurs during Alzheimer's disease. At the same time, memory also improved.
Here we have reported the main phenolic acids and their neuroprotective action. However, there are also other compounds, capable of counteracting neurodegeneration, such as ellagic acid, found in berries, nuts and pomegranates, or cinnamic aldehyde, found in cinnamon.
Therefore, it is clear the importance of a healthy and varied diet, which includes fruit, vegetables, spices and aromatic herbs, to counteract inflammation, oxidative stress and to keep brain degeneration at bay.