The surprising connection between your gut and brain health
Scientists are discovering the truth behind the phrase, “Think with your gut.” Your gut, and the bacteria that live in it, shape our thoughts and moods. Startling research shows the implications this has on Alzheimer’s, Parkinson’s, and general mental health.
“All disease begins in the gut,” said Hippocrates, the so-called father of modern medicine. And emerging scientific research shows just how intertwined our gut health is with our brain health—all thanks to trillions of little bacteria.
“Hippocrates’ quote may appear to be a bit of an overstatement,” says neurologist Dr. David Perlmutter. “But we now recognize that the genesis of these maladies—Alzheimer’s disease, Parkinson’s disease, and even non-neurological problems such as type 2 diabetes—is strongly influenced by the gut.”
Perlmutter says that once you see the benefits, you’ll do “everything you can to cater to the health and diversity of the bacteria that reside within your intestines.”
Your digestive system doesn’t just break down your food. It also functions as part of your nervous system.
“Your intestinal tract has 100 million nerves that ‘talk’ back and forth with your brain,” reports Dr. Rusha Modi, an academic gastroenterologist. He says it acts like a second brain, influencing your thoughts and actions. “We’re learning, in essence, the mechanisms behind phrases such as ‘I have a gut feeling.’”
Take serotonin, for example. It’s one of the primary neurotransmitters that influences our mood and memory, and it may even play a role in the development of Parkinson’s disease and obesity. “Most of it actually comes from and is stored in our intestinal tracts,” says Modi.
Just how much of your serotonin, exactly? A whopping 90 percent. And here’s the fascinating part: researchers now think that beneficial gut bacteria help produce serotonin and other neurotransmitters, visibly changing our behaviour and mental health.
“You have an entire nervous system in your gut, and bacteria directly interact with your brain through their effects on the nerves in the gut,” summarizes naturopathic doctor Tara Nayak.
“Bacteria release neuro-transmitters and hormones. You feed the bacteria, and they release end products that change the way your brain responds. We live in a tightly woven symbiotic relationship with our gut bacteria!”
This relationship can go awry when our gut has an imbalance of bacteria and lets harmful bacteria flourish.
The number of children diagnosed with autism spectrum disorder (ASD) has doubled in the last decade. Today, it’s the most commonly diagnosed and fastest growing neurological disorder in Canada.
Since it’s a neurodevelopmental disorder, and we now know our gut is part of our neurological system, the fact that up to 70 percent of children with ASD are thought to experience gastrointestinal problems raises questions. Autism nonprofits are pouring funding into looking at this gut-brain connection.
The results from dozens of studies are promising. Researchers have found that transplanting beneficial micro-organisms into the gut of children with ASD reduced constipation and other gastrointestinal problems by 80 percent, while also significantly improving ASD symptoms.
And in animal trials, mice with autistic behaviours that were given probiotics became visibly less anxious and more social after the treatment.
In a few years, the number of Canadians with dementia will rise by a staggering 66 percent, according to Alzheimer Society Canada.
One animal study found that some gut bacteria produce a type of biofilm that provokes the same brain inflammation as the plaques linked with Alzheimer’s disease (AD).
In another study, scientists noticed the type of bacteria in mice with AD were different from those in mice that didn’t have AD. So they took gut bacteria from the sick mice and transplanted it into healthy mice, after which the healthy mice started developing plaques in their brains linked with the development of AD.
“Our study ... shows a direct causal link between gut bacteria and Alzheimer’s disease,” concluded researcher Frida Fåk Hållenius in a press release.
Researchers have found similar bacteria differences in humans. “These findings add Alzheimer’s to the growing list of diseases associated with gut microbial alterations,” warns a study published in the Scientific Reports journal.
After Alzheimer’s disease, Parkinson’s disease (PD) is the second most common neurodegenerative disease.
One of the earliest symptoms of PD, long before any neurodegenerative symptoms appear, is constipation. The Michael J. Fox Foundation funded research on this and discovered that different bacteria live in people with the disease than those without PD.
The foundation also found that, in contrast with healthy people, those with PD have alpha-synuclein (a type of protein) present in both their brain and gut.
People with PD often have a leaky gut where substances can pass from the intestines into the body. Researchers suspect this may allow the protein to spread from the gut to the brain. A leaky gut may also allow harmful bacteria, and the inflammatory substances these bacteria produce, to spread throughout the body.
To test whether PD spreads from the gut to the brain, researchers compared study participants who had their vagus nerve (which connects the gut-brain axis) surgically cut, to those who had not. They found a potential protective effect with a certain type of the surgery.
Taking care of your gut and avoiding bacteria imbalances isn’t just about dodging a brain malady. When it comes to everyday living, our guts hold one of the keys to happiness.
“[Bacteria] and gut inflammation have been directly linked to anxiety and depression, and there’s evidence that probiotics can be effective in preventing these issues,” says Nayak.
In studies, people given beneficial bacteria had reduced cortisol, a marker of stress.
The American Psychological Association even notes that, extrapolating from a mouse study, changing our gut bacteria may make you bold and adventurous if you’re shy. Plus, gut flora has been tied to learning potential and memory, as well as mental calmness.
“An obvious measure of gut health is digestion,” says Nayak. “If you’re not moving your bowels daily, there’s a problem!” She says gas, bloating, belching, heartburn, or any other digestive complaints are often the first sign of a gut that’s out of balance.
While researchers continue to dig deep into the gut-brain axis, knowing the implications for your brain health means you might never take those unseen bacteria for granted again.
“The best choices ... have at least 12 to 15 different types of bacteria and at least 30 billion organisms,” says neurologist Dr. David Perlmutter. As always, check with your health care practitioner first.
“Ensure the beneficial bacteria get what they need to do their job,” says Perlmutter. “Prebiotic fibre is important for brain health, mood, and cognitive function.” He recommends foods such as dandelion greens, onions, garlic, and chicory root.
“The standard Western diet has been associated with a loss of richness of bacteria,” says gastroenterologist Dr. Rusha Modi. “Ecological diversity tends to mirror nutrient diversity. Maximize the variety of foods you eat. One tip I use myself is to look for one new fruit or vegetable to put into my cart when I go grocery shopping.”
“We overuse them,” warns Modi. “They deplete your healthy gut bacteria.”
Sweat a little
Aerobic exercise expands your brain’s hippocampus (responsible for learning and memory), which is important for dementia prevention.
“Spending time outdoors and having natural light exposure increases vitamin D levels, improves mood, and alleviates some symptoms of depression,” says Dr. Rusha Modi.
A third of dementia cases are thought to be caused by blood flow problems, so a healthy heart can mean a healthy brain. Eat more plants and less sodium, and find healthy ways to reduce stress.
They are supplements that may improve brain function and include fish oils, resveratrol, and Ginkgo biloba.