By Annell St. Charles, Ph.D., R.D.
Inflammation has been mentioned as one contributor to cognitive dysfunction. Evidence suggests that inflammation is associated with age-related cognitive decline and may play a role in risk for dementia, including Alzheimer’s disease.
Potential pro-inflammatory sources of irritation/infection include:
- microbial and viral infections.
- exposure to allergens, radiation, and toxic chemicals .
- autoimmune and chronic diseases.
- excess alcohol.
- tobacco use.
- a high-calorie diet.
There are two stages of inflammation: acute and chronic. Acute inflammation results from activation of the immune system, persists for only a short time, and is usually beneficial for the repair and healing of the damaged tissue and in removing invading pathogens. Chronic inflammation lasts for a longer period of time and may increase the risk of various long-lasting illnesses.
The relationship between inflammation and oxidative stress is two-fold. On one hand, inflammation leads to an increased uptake of oxygen, resulting in an increased release of free radicals and their metabolites (called reactive oxygen species). The inflammatory response also increases production of substances that further recruit inflammatory cells to the site of damage, resulting in the production of more reactive species. In simple terms, inflammation triggers a cycle that produces more inflammation, and the cycle is accompanied by an increase in oxidative stress.
A large body of research suggests that inflammation in the central nervous system increases with age, in part due to an increase in activation of microglia cells, which promotes a pro-inflammatory response. Microglia cells make up approximately 20 percent of the cell population of certain regions of the brain, and their activation would result in significant brain cell inflammation.
The diet can be a source of nutrients and non-nutrient constituents that can modulate inflammatory processes and, thus, aide cognitive function. Plant foods are considered a particularly rich source of anti-inflammatory substances. Diets high in fruits and vegetables are inversely associated with the risk of inflammation. In particular, carotenoids and flavonoids seem to reduce inflammatory processes.
Blueberries have been found to have one of the highest anti-inflammatory/antioxidant capacities of all fruits and vegetables. One study showed that daily ingestion of one cup of blueberries increased natural killer cell counts (helps to regulate the immune response to injury or infection), and a one-time ingestion of 1.5 cups reduced oxidative stress and increased anti-inflammatory cytokines. Research has also demonstrated that blueberry extract may inhibit one of the primary steps in the inflammatory stress pathway by reducing activation of microglia cells.
Pterostilbene is the natural dietary compound that contributes to the primary antioxidant component of blueberries. Research suggests that pterostilbene may have numerous preventive and therapeutic properties in a wide range of human diseases, including neurological/cognitive disorders.
Researchers have also demonstrated a high level of antioxidant and anti-inflammatory compounds in many other plant foods. In particular, the polyphenolic compounds contained in berries of all types, walnuts, curcumin, and fish oils have been found to provide potent antioxidant and anti-inflammatory activities that may reduce the age-related sensitivity to oxidative stress or inflammation, which would, in turn, alter neurodegeneration.