Microbes: Masters of Food and Mood
Life is not easy for bacteria; people fight them off with everything from wipes and sprays to hand sanitizers, often forgetting the huge role the tiny organisms play within their bodies. The gut microbiota, the intricate ecosystem of bacteria found within the human intestine, contains at least 1000 different species that help humans break down food and fight disease. According to an interview with Yolanda Sanz at the Institute of Agrochemistry and Food Technology (IATA) of the Spanish National Research Council in Spain, these microbes may also provide insight into human behavior, including psychological disorders such as depression.
People gain most of these microbes soon after birth. Throughout the rest of their lives, they form a “bacterial fingerprint,” a microbial identity unique to them that is shaped by several different influences:
Through studies done with mice, researchers have found that this bacterial fingerprint may be connected to the brain and mood. For example, when injected with the intestinal bacteria of an outgoing species of mice, a shy species of mice became similarly outgoing. Additionally, mice injected with the gut microbiota of depressed human patients displayed similar symptoms of depression. These effects are likely due to intestinal bacteria producing neurotransmitters, chemical substances that allow nerve impulses, or blood-brain barrier metabolites, molecules that determine what substances move from the body to the brain.
People gain most of these microbes soon after birth. Throughout the rest of their lives, they form a “bacterial fingerprint,” a microbial identity unique to them that is shaped by several different influences:
- Aging: In the first two to three years of a person’s life, gut microbiota is extremely sensitive to one’s diet, including whether he or she was breastfed. In adulthood, the composition of gut microbiota becomes more stable as the person adapts a more diverse diet. In old age, however, this diversity decreases, so the microbes become unstable once again.
- Diet: A drastic change in eating habits can change the abundance of certain bacterial strains in a person’s gut by about 30% to 40%. Changing the intake of protein, fiber, or fat can significantly alter a person’s bacterial fingerprint.
- Drugs: Medications such as antibiotics or anti-inflammatory drugs affect the composition of a person’s gut microbiota.
Through studies done with mice, researchers have found that this bacterial fingerprint may be connected to the brain and mood. For example, when injected with the intestinal bacteria of an outgoing species of mice, a shy species of mice became similarly outgoing. Additionally, mice injected with the gut microbiota of depressed human patients displayed similar symptoms of depression. These effects are likely due to intestinal bacteria producing neurotransmitters, chemical substances that allow nerve impulses, or blood-brain barrier metabolites, molecules that determine what substances move from the body to the brain.
Image Source: Geralt
Sanz acknowledges that much more research must be done to understand how bacteria interacts with the nervous system, but she remains optimistic about current progress. Patients with depression have responded positively to probiotics, substances that stimulate the growth of microorganisms like gut microbiota.
Greater knowledge of the effect bacteria has on the brain can lead to the development of more effective treatments for psychological disorders. With an improved understanding of the biological basis of depression, researchers can better stop the disorder at its roots before it overbears its sufferers. Examining the relationship between physical and mental health can bring medicine closer to healing not only the human body but also the human soul.
Greater knowledge of the effect bacteria has on the brain can lead to the development of more effective treatments for psychological disorders. With an improved understanding of the biological basis of depression, researchers can better stop the disorder at its roots before it overbears its sufferers. Examining the relationship between physical and mental health can bring medicine closer to healing not only the human body but also the human soul.
Featured Image Source: "Wild garden of the gut bacteria 6" by Dr. Nicola Fawcett is licensed under CC BY-SA 4.0
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