The relationship between gut health and brain function is drawing increasing attention from researchers worldwide. A growing body of evidence suggests that the gut microbiome—a vast and complex community of bacteria, fungi, and viruses in the digestive tract—may play a significant role in supporting brain health and even help prevent neurodegenerative conditions such as dementia.
The Gut-Brain Axis
The gut and brain are closely connected through what scientists call the gut-brain axis, a bidirectional communication network involving the vagus nerve. Professor Simon Carding, who leads the Food, Microbiome and Health Research Programme at the Quadram Institute in Norfolk, United Kingdom, describes the gut as the body’s “second brain.” He explains that it contains the largest concentration of neurons outside the brain, which allows it to directly influence central nervous system activity.
Gut bacteria produce short-chain fatty acids, neurotransmitters such as dopamine and histamine, and hormones that regulate appetite and inflammation—all factors known to affect cognitive function. Some of these bacteria even generate compounds structurally similar to beta-amyloid, a protein associated with Alzheimer’s disease. These substances may travel from the gut to the brain via neural pathways and contribute to the formation of amyloid plaques.
Inflammation and Aging
As people age, the makeup of their gut microbiome changes, often becoming less diverse and more vulnerable to harmful bacteria. This shift is influenced by reduced dietary variety, increased use of medications, and chronic illnesses such as type 2 diabetes. These changes are linked to a phenomenon known as “inflammaging,” which refers to chronic, low-grade inflammation associated with aging.
This systemic inflammation can increase gut permeability, which may allow inflammatory agents and potentially harmful proteins to enter the bloodstream and affect the brain. Research involving aged mice has shown that a high-fiber diet helps reduce neuroinflammation and improve memory. The beneficial effects are believed to be mediated by short-chain fatty acids produced by fiber-digesting gut microbes, which help calm immune responses in the brain.
The Role of Diet
Nutritional therapist Katia Demekhina, based in Hong Kong, emphasizes that dietary diversity is crucial to cultivating a robust and beneficial gut microbiome. She recommends aiming for 30 different plant-based foods per week to ensure a wide range of fiber and nutrients. “Fibre is fuel for our gut bacteria,” Demekhina explains. “It encourages the growth of beneficial microbes that support both immune and brain health.”
While fermented foods such as kefir, yogurt, kombucha, and sauerkraut are popular for their probiotic content, Demekhina warns that probiotics alone are insufficient. “We also need to create the right internal environment for these bacteria to thrive, which depends on fiber, hydration, and overall dietary balance,” she says.
Clinical studies have demonstrated that dietary interventions, including probiotic supplementation, can improve cognitive function in individuals with mild cognitive impairment (MCI) and early Alzheimer’s disease. However, experts caution that more research is needed to determine which specific interventions are most effective.
Oral Health and Brain Function
Emerging research is also exploring the role of the oral microbiome in brain health. A study from Rush University in Illinois found that older adults with higher levels of harmful oral bacteria performed worse on cognitive tests, even if they had not been diagnosed with dementia. Darbaz Adnan, a PhD candidate involved in the study, speculates that these bacteria may reach the gut or brain and contribute to inflammation or amyloid plaque formation.
Maintaining oral hygiene may therefore be an important factor in protecting both cardiovascular and cognitive health. Regular dental checkups, brushing, and flossing could help reduce the risk of neurodegenerative disease by limiting the entry of harmful microbes into the bloodstream.
Gender Differences and Microbial Profiles
Recent findings suggest that the gut microbiome may differ between sexes, potentially influencing dementia risk. Aged female mice have shown greater gut inflammation and reduced levels of neuroprotective short-chain fatty acids compared to males. Hormonal changes, especially reductions in estrogen, may also contribute to reduced microbial diversity in aging women, possibly explaining their higher prevalence of Alzheimer’s disease.
Lifestyle-Based Prevention Strategies
Although there is currently no cure for dementia, researchers believe that modifying the gut microbiome through diet and lifestyle may offer a powerful preventive strategy. Professor Carding stresses the importance of non-pharmaceutical approaches. “This is one area where we can make a difference ourselves,” he says. “Diet is a modifiable factor that could reduce our risk of cognitive decline.”
Understanding the gut-brain axis opens new avenues for both research and practical health measures. While more scientific investigation is needed, many experts agree that nurturing a healthy microbiome is one of the most promising ways to protect cognitive function over time.
Practical Steps for Gut and Brain Health
Experts recommend the following evidence-based practices to support the gut microbiome and reduce the risk of dementia:
Consume a varied, plant-rich diet with a goal of 30 different plant foods per week
Prioritize high-fiber foods such as legumes, whole grains, fruits, and vegetables
Include fermented foods like yogurt, kimchi, and kombucha regularly
Practice consistent oral hygiene and seek routine dental care
Avoid unnecessary antibiotic use
Engage in regular physical activity and maintain social connections
Manage chronic conditions, especially those related to metabolism and cardiovascular health
As awareness of the gut-brain connection grows, these simple yet powerful lifestyle strategies could help individuals maintain both mental and physical health well into old age.
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