Unblocking the Fountain of Youth: Diet and exercise have a major impact on cognition in older adults

Given the vast number of people in the United States approaching age 65, interdisciplinary research into factors influencing the trajectory of cognition and brain aging in older adults is needed. In a recent review posted in nutrients, Researchers examine the collective effect of diet and exercise interventions on age-related cognition and brain health changes.

Study: Impact of diet and exercise interventions on cognition and brain health in older adults: A narrative review. Image Credit: Isarat/Shutterstock.com

Age-related cognitive decline

Decreased processing speed is one of the main cognitive deficits observed in the elderly, in addition to impairment of semantic and episodic memory. Similarly, working memory that actively holds short-term information to enable goal-directed decision-making also decreases as a result of aging.

Impaired working memory results in a corresponding reduction in executive functions in old age. Due to structural and functional changes in the brain, aging also affects an individual’s crystallized and fluid intelligence.

Structural changes in the brain associated with aging include reductions in gray matter volume and cortical thickness. Gray matter volume, a measure of neuronal and glial cell bodies, decreases in volume within multiple brain regions, including the medial temporal lobe of the hippocampus and entorhinal cortex during aging. In particular, the age-related reduction in hippocampal volume, resulting from neuronal cell loss and decreased neurogenesis, is associated with decreased cognitive performance on memory, spatial learning, and emotional regulation tasks.

Effect of diet and exercise on aging

It is essential to understand the relationship between nutrient consumption and neuronal function, neurometabolic processes and cognitive decline.

There is growing evidence that nutrients from various foods in multiple food groups have synergistic effects beyond the effects of individual nutrients. For example, vitamin absorption from green salad improves when served with olive oil and vinegar rather than a fat-free ranch dressing.

To date, the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) and Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diets are the most frequently cited in the literature. Each of these diets appears to improve neurological signs of aging, including cell membrane and vascular integrity, inflammation, resolution and oxidation, as well as lipid and glucose metabolism.

Considerable evidence suggests that the Medi and MIND diets are associated with both general and domain-specific aspects of cognition. For example, several studies have associated the Medi diet with attention and long-term memory. Similarly, adherence to the MIND diet is positively associated with visuospatial ability, perceptual speed, and executive function.

The impact of ketogenic diet (KD) and intermittent fasting (IF) on cognition and brain function has also been extensively studied, as weight management diets appear to improve cognitive functioning. Similarly, weight loss achieved through bariatric surgery improves attention, memory and executive function.

In addition to diet, exercise positively affects cognition, as demonstrated by a previous study in which overweight and obese adults were enrolled in a year-long behavioral weight loss intervention. These patients followed a low-calorie diet, a low-calorie diet with 150 minutes of moderate-intensity exercise each week, or a low-calorie diet with 250 minutes of exercise each week.

After the surgery, weight decreased markedly in both groups. More specifically, the high exercise group improved their performance on the Iowa Gambling Task (IGT) reward compared to the other two study groups. Overall, more exercise with behavioral weight loss regimens had an additional benefit on executive functioning, even without weight loss benefits.

Endurance exercise typically includes walking, jogging, running, swimming, and biking, with walking being the form most practiced among seniors. Higher levels of endurance fitness are associated with less age-related brain volume decline.

Randomized controlled trials examining the role of resistance exercise on cognition have yielded conflicting results. However, all the evidence suggests that resistance exercise in the elderly improved cognitive performance, visual attention and memory, promoted brain plasticity, and weakened hippocampal atrophy.

Similarly, a recent systematic review found that resistance training positively affected global executive and cognitive functions in older adults. This form of exercise also had a positive impact on memory, albeit weakly, and did not significantly improve attention. Furthermore, the three-weekly training, compared with the two-weekly resistance training, positively affected general cognitive abilities.

No evidence of an interfering effect of aerobic and resistance training was reported. However, the literature comparing resistance or combined exercise with a no-exercise control is limited. Therefore, it is unclear which exercises should be prescribed to maintain and improve cognition and brain health among older adults.

Behavioral interventions such as yoga appear to mitigate age-related and neurodegenerative decline. In a review examining the effects of yoga practice on brain structures, function, and cerebral blood flow, yoga positively affected the structure and function of the hippocampus, prefrontal and cingulate cortex, amygdala, and neuronal networks .

A recent literature review evaluating the effect of tai chi, a traditional Chinese martial art, on brain structure and neurobehavioral changes found that this form of exercise also increases cortical gray matter volume, improves activity and neural homogeneity and increases neural connectivity in the frontal, temporal and occipital lobes, cerebellum, and thalamus.

Conclusions

All diets evaluated in this review addressed factors associated with aging and neurodegenerative diseases such as Alzheimer’s disease and related dementias (ADRD). Depending on the type and intensity, exercises have been found to positively influence cerebral vasculature, neurotransmitter regulation, growth factors and neurogenesis.