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As life expectancy lengthens for most of the world, the incidence of dementia and cognitive decline is also increasing. The number of people affected by dementia is growing exponentially, with an estimated 55 million people diagnosed worldwide today and 139 million predicted to be diagnosed by 2050.¹ In the United States, an estimated 6.07 million adults 65 years or older were living with clinical Alzheimer’s Disease in 2020,² and US-based studies continue to report a disproportionate burden of dementia and mild cognitive impairment among older Black and Hispanic adults.^2,3 

Age-related cognitive decline may be a health concern for some patients, especially those with a family history or increased genetic risk for neurodegenerative disease. Multi-pronged lifestyle interventions offer promise for the prevention and delay of cognitive decline.^4,5 For example, personalized dietary plans that include neuroprotective foods provide nutrients for optimal cognitive functioning and potentially reduce neuroinflammation, as well as improve brain plasticity.^6,7

Neuroprotective Nutrients

Nutrition is a key modulator of cognitive health, but what are those specific nutrients and vitamins that support cognition and reduce neurodegeneration? An important consideration is mitochondrial health. Age-related neurodegeneration has been associated with oxidative stress, flawed energy metabolism, and mitochondrial dysfunctions.^8,9 In animal studies, a variety of vitamins and nutrients have demonstrated protective effects on mitochondria, including coenzyme Q10 (CoQ10),¹⁰ acetyl-L-carnitine (ALC),¹¹ and resveratrol.¹¹ And clinical studies have also suggested a role for ALC and resveratrol in the potential delay of cognitive decline.^12,13 The coenzyme nicotinamide adenine dinucleotide (NAD) also influences many key cellular functions, including processes that are critical for maintaining metabolic homeostasis and for healthy aging.¹⁴ In the following video, IFM educator Robert Rountree, MD, explores the latest research on this coenzyme:

Whole Diet Approaches for Cognitive and Brain Health

Nutrient-dense anti-inflammatory diets have been associated with reduced risk of many chronic diseases.¹⁵ Research has also shown that healthy nutrition habits, including diets that are high in phytochemicals and antioxidants, may be neuroprotective, may support cognition, and may even slow neurodegeneration.^16,17

Epidemiological and observational studies, as well as clinical trials, continue to demonstrate that higher adherence to specific diets that prioritize plant, whole grain, and healthy fat intake, such as the Mediterranean, DASH (Dietary Approaches to Stop Hypertension), and MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) diets, is associated with less cognitive decline and reduced risk of dementias such as Alzheimer’s disease.^18-25 For example, a 2021 observational study used questionnaires to evaluate the effect of Mediterranean diet adherence on the cognitive abilities and psychological state of 2,092 men and women (65 years or older) from seven different Greek cities.¹⁹ Results from the study indicated that higher diet adherence was significantly associated with both better cognitive status and less depression symptoms.¹⁹ In addition, a 2022 meta-analysis of 26 cohort studies found that higher adherence to the Mediterranean diet was associated with a lower risk of mild cognitive impairment (RR=0.75; CI: 0.66-0.86) and Alzheimer’s disease (RR=0.71; CI: 0.56-0.89) among healthy adults.¹⁷ 

Brain Structure & Function

In addition to affecting cognitive scores, nutrition also affects underlying brain structures. As one example, polyphenols in foods have anti-inflammatory effects on microglia.²⁶ Further, poor nutrition, such as consuming a Western diet, has been correlated with reduced hippocampal volume²⁷ while intake of fish oil has been suggested to exert beneficial effects on white matter microstructural integrity and gray matter volume.²⁸ A 2022 observational study (n=1,412 older adults followed for a median of 9.7 years) found that higher adherence to a MIND diet was associated with lower dementia risk and with preserved white matter microstructure.²⁹ In addition, a first-of-its-kind systematic review published in 2020 evaluated 14 cross-sectional and longitudinal studies that measured dietary patterns, neuroimaging correlates, and neurocognitive tests.³⁰ Most of the included studies assessed adherence to the Mediterranean diet, and the following are some of the review’s results:³⁰

• Higher adherence to the Mediterranean diet correlated with larger total and regional brain volumes and higher white matter integrity.
• High adherence to the diet was associated with lower diffusivity (markers of microstructural changes) and in turn was associated with higher cognitive scores.
• Low adherence to the diet was associated with increased beta-amyloid in the left frontal-parietal cortex.
• Total gray matter volume was positively associated with the Mediterranean diet as well as fish consumption and negatively associated with other meat intake. Total white matter volume was positively linked with the Mediterranean diet.
• Overall, the Mediterranean diet and other assessed nutrient patterns (such as intake of vitamins, antioxidants, and fiber) were associated with white matter integrity, functional connectivity, total and regional brain volumes, and glucose metabolism.

THE ROLE OF THE GUT microbiota

The effectiveness of dietary approaches that protect against age-related cognitive decline may be linked to modulation of the gut microbiota structure and function.^16,31 An optimal gut microbiome potentially improves the function of an aging brain,³² but research on specific possible mechanisms is limited,³³ and some studies have shown neutral results. A 2020 randomized controlled trial investigated the association between diet, intestinal microbiota, and cognition in 226 healthy adults.³⁴ Dietary intake, cognitive functioning, and fecal samples were assessed. Plant-rich diets were positively correlated with anti-inflammatory microbial species, and animal product–rich diets were associated with a pro-inflammatory microbial profile; however, no association was found between cognition and microbiota composition.³⁴ Research continues to explore the associations between neuroinflammation and gut dysbiosis and what role any alterations in the gut microbiota may play in cognitive health and prevention of neurodegeneration.³⁵

Clinical understanding of how nutrition and lifestyle factors support cognition and optimal brain function continues to evolve.³⁶ Learn more about tools and strategies to help patients achieve sustainable lifestyle change and improve their well-being through IFM’s new course Lifestyle: The Foundations of Functional Medicine.

Related Articles

A Multi-Pronged Approach for Cognitive DeclineCan Diet Cut Mild Cognitive Impairment Risk in Half?Neurodegenerative Disease: Improving Outcomes Through Nutrition

References

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