How can the organisms in your gut affect your brain?
Your gut contains 2.2 pounds of microorganisms. Bacteria, fungi, protists and viruses all share real estate in the lining of your intestine. These organisms make up your intestinal microbiome. We observe changes to the intestinal microbiome in a variety of neurologic and psychiatric diseases. They include multiple sclerosis, Parkinson’s disease, Alzheimer’s disease, depression and anxiety, among others.
Your gut constantly communicates with your brain. The intestinal microbiome plays a large role in this. There are two possible methods of communication:
- The first is making “stuff” and sending it via the blood stream to the brain. Bacteria are able to make a variety of neurotransmitters (including serotonin, dopamine, and noradrenaline) as well as other things, like fatty acids and inflammatory molecules which can make their way into the blood stream then travel up to the brain, and through an indirect route, affect brain function.
- The second method of communication is more direct. The main nerve connecting the gut to the brain is the vagus nerve. One study found that elimination of a specific type of bacteria in the gut led to changes in the expression of particular types of receptors in parts of the brain. However, when they repeated the experiment after cutting the vagus nerve, these changes were not observed, suggesting a role for the vagus nerve in carrying out this change.
What do we currently know about migraine and the microbiome?
There are a limited number of studies available on this association.
One study found that people with migraine have more bacteria, particularly in their mouth, that can produce a gas called nitric oxide (a known migraine trigger).
A series of studies examines the stomach bacterium H. pylori, which can cause ulcers. These studies have yielded conflicting results.
Finally, a recently published, well-designed randomized controlled trial in which subjects with migraine were given either a probiotic or placebo taken daily for 12 weeks found no differences in their outcomes. We do not currently recommend probiotic supplements for migraine.
As you can see, there is much to learn regarding the relationship between the gut microbiome and migraine. We at the University of Vermont Headache Clinic are conducting a study investigating this relationship.
If you have migraine and are interested in finding out more about our migraine-microbiome research study, click here.