Researchers Confirm Link Between Alzheimer’s and Gut Microbiota

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Key Takeaways

  • Imbalances in gut microbes could contribute to amyloid plaques in the brain, and raise risk of Alzheimer's disease, researchers suggest.
  • Researchers noted that previous studies have shown that those with the condition tend to have altered gut microbiota compared to those without dementia.
  • There are numerous lifestyle strategies that can boost gut health, including healthy eating, exercise, stress management, and getting quality sleep.

What's good for the gut might benefit the brain, researchers suggest, noting that imbalances in the gut microbiota could contribute to development of Alzheimer's disease, the most common cause of dementia.

In research published in the Journal of Alzheimer's Disease, a team of Swiss and Italian researchers found that proteins produced by certain intestinal bacteria could modify the interaction between the immune and nervous systems. That modification may lead to development of amyloid plaques in the brain, previously found to raise risk significantly for Alzheimer's.

Strong Connection

To reach their conclusions, researchers looked at 89 people between 65 and 85 years old, with some of the participants diagnosed with Alzheimer's disease, but others with no memory issues at all. Using imaging, they were measured for amyloid deposits and had blood checked for inflammation markers and proteins produced by intestinal bacteria.

"We have already shown in other research that gut microbiota composition in patients with Alzheimer's disease was altered, compared to people who do not suffer from such disorders," says lead researcher Giovanni Frisoni, M.D., director of the Memory Centre at University Hospitals of Geneva.

"Their microbiota has a reduced microbial diversity, with an overrepresentation of certain bacteria and a strong decrease in other microbes," he says. "In this research, our results are indisputable. Certain bacterial products of the intestinal microbiota are correlated with the quality of amyloid plaques in the brain."

The Gut-Brain Axis

Although the recent research focuses on Alzheimer's, it's not just prevention of neurodegenerative conditions that should prompt a closer look at gut health strategies for many people.

The role of the gut for overall cognitive function—and vice versa—is so well established that the gut has often been called "the second brain" and is thought to be crucial for emotional wellbeing in addition to digestive health.

The gut-brain axis is a bidirectional superhighway of chemical signals sent between the brain and the digestive system, and those messages are vital for supporting your autonomic nervous system, endocrine system, and immune system.

Lisa Mosconi, PhD

You might be making changes for better digestion, but then discover benefits like clearer thinking, feeling calmer, and improving your memory.

— Lisa Mosconi, PhD

A major example is serotonin, a neurotransmitter that has a range of functions in the body, and is so integral to mood and overall well-being that it's called "the happy chemical." Although it plays a major role in brain function, it's estimated that 90% of your serotonin is made in the digestive tract.

"You simply can't separate the brain from the gut and treat them as two independent units in the body, since they're so connected," says Lisa Mosconi, PhD, author of Brain Food: The Surprising Science of Eating for Cognitive Power. What affects one will often affect the other, she adds.

For example, emotional stress can lead to digestive upset, and poor digestive function can prompt anxiety. The good news, she adds, is that you can use this connection to improve both.

"Lifestyle changes geared toward improving gut health can have a great impact on your brain as well," says Mosconi. "You might be making changes for better digestion, but then discover benefits like clearer thinking, feeling calmer, and improving your memory."

Simple Changes, Big Effects

Diet plays a large part in implementing better gut health, and Mosconi recommends:

  • Proteins from lean meat and fish, which are broken down into amino acids that form the basis of brain cells.
  • Vegetables, fruits, and whole grains to provide important carbohydrates such as glucose, giving the brain much-needed fuel.
  • Healthy fats like omega-3 fatty acids support the immune system and lower inflammation, and shielding your brain from damage.
  • Fermented foods can increase the amount of beneficial bacteria in the gut, improving both gut and brain health.
  • Adequate hydration from water, since brain cells require a balance of water and electrolytes for cells to function properly.

What This Means For You

In addition to food, there are other strategies that have been shown to have a positive effect on gut health. Exercise, de-stress practices, and getting fresh air have all been shown to improve your gut, and one particularly potent step would be to get more quality sleep.

For example, a study published in Sleep Medicine found that there’s a relationship between gut microbiome composition, sleep habits, and cognitive flexibility.

Not only does sleep help your microbiome, but it works the other way as well. A healthy gut will give you a better night of sleep, according to W. Christopher Winter, MD, president of Charlottesville Neurology and Sleep Medicine, and author of The Sleep Solution.

"Sleep disturbances can contribute to gastrointestinal issues, and that can worsen your sleep problems," he says. "Basically, whatever your goal might be, whether it's better gut health or improved brain health, it's easiest to start with establishing good habits around the basics, like sleep, food, exercise, and mindfulness."

3 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Marizzoni M, Cattaneo A, Mirabelli P, et al. Short-chain fatty acids and lipopolysaccharide as mediators between gut dysbiosis and amyloid pathology in alzheimer's diseaseJ Alzheimers Dis. 2020;78(2):683-697. doi:10.3233/JAD-200306

  2. Terry N, Margolis KG. Serotonergic mechanisms regulating the GI tract: experimental evidence and therapeutic relevanceHandb Exp Pharmacol. 2017;239:319-342. doi:10.1007/164_2016_103

  3. Anderson JR, Carroll I, Azcarate-Peril MA, et al. A preliminary examination of gut microbiota, sleep, and cognitive flexibility in healthy older adultsSleep Med. 2017;38:104-107. doi:10.1016/j.sleep.2017.07.018

By Elizabeth Millard
Elizabeth Millard is a freelance journalist specializing in health, wellness, fitness, and nutrition.