Millions of microscopic, single-celled organisms live in the human body, and most of them play a beneficial role in keeping people healthy, Dr. Gary Small, director of behavioral health breakthrough therapies at Hackensack Meridian Health in New Jersey, told Newsmax on Thursday.
However, Small said on Newsmax's "National Report" that the gut microbiome, or the mix of bacteria and other microbes in the digestive tract, can also affect the brain in multiple ways, including inflammation and the production of neurotransmitters tied to how people think and feel.
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"Some of them are healthy. Some of them are unhealthy," Small said of gut microbes, adding that certain bacteria "can actually leak out of the gut and seep into our bloodstream and go right up into the brain."
Small said that the process can worsen inflammation, which he linked to depression symptoms and memory problems.
"They can heighten inflammation, which we know will enhance feelings of depression, affect our memory," he said.
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Small also warned that some microbes may produce "amyloid-like proteins" that can be harmful to the brain.
He said researchers have also found that gut bacteria can produce neurotransmitters — brain chemicals that influence mood and cognition.
"It's remarkable they actually produce neurotransmitters that go into the brain," Small said. "These brain messengers that can alter how we think and how we feel."
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Small said diet and daily habits can help people shift the balance toward healthier gut microbes, pointing to evidence supporting the idea behind the phrase "you are what you eat."
He recommended a high-fiber diet rich in fruits, vegetables, and whole grains to support beneficial bacteria.
The doctor described certain high-fiber foods as "prebiotics," including items such as onions and apples, which can help nourish helpful microbes in the gut.
Small also highlighted probiotics, or foods that introduce live beneficial bacteria, including fermented options such as yogurt, kefir, and sauerkraut.
Beyond food, Small emphasized lifestyle choices that can support gut and brain health, including managing stress, getting consistent sleep, exercising regularly, and limiting processed foods high in refined sugar.
Asked for a short list of foods to add to a meal immediately, Small recommended green leafy vegetables, colorful fruits, and healthy fats.
"People think that fat is bad for you, but fats from olive oil and avocados, these are healthy fats," he said.
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