Migraine sufferers have significantly more nitrate-reducing microbes in their mouths than people who do not get migraine headaches, says a study out of UC Dan Diego School of Medicine published in mSystems. What the researchers don’t know is if the bacteria are a cause of migraine or a result, but the scientists are excited to try to find out.
“There is this idea out there that certain foods trigger migraines — chocolate, wine and especially foods containing nitrates,” said first author Antonio Gonzalez, a programmer analyst in the laboratory of Rob Knight, PhD, professor and director of the Center for Microbiome Innovation at UC San Diego. “We thought that perhaps there are connections between what people are eating, their microbiomes and their experiences with migraines.”
Nitrates, which are found in foods like processed meats and green leafy vegetables, and in certain medicines, can be reduced by bacteria found in the mouth. When circulating in the blood, these nitrites can then be converted to nitric oxide under certain conditions. Nitric oxide is good for cardiovascular health because it improves blood flow and reduces blood pressure. Interestingly, approximately four out of five people who take drugs with nitrates for chest pain or congestive heart failure report severe headaches as a side effect.
Using data from the crowdfunded American Gut Project managed by the Knight Lab, Gonzalez and colleague Embriette Hyde, PhD, sequenced bacteria found in 172 oral samples and 1,996 fecal samples from healthy participants who had filled out surveys indicating whether they suffered from migraines or not.
The gene sequencing showed that bacterial species were found in different abundances between people who get migraines (migraineurs) and those who do not.
They then used a bioinformatic tool called Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) to analyze which genes were likely to be present in the two different sets of samples. They found slight but statistically significant increase in the abundance of genes that encode nitrate, nitrite and nitric oxide-related enzymes in migraineurs’ fecal samples. Those genes were even more significantly abundant in the oral samples.
“We know for a fact that nitrate-reducing bacteria are found in the oral cavity,” said Hyde, project manager for the American Gut Project and assistant project scientist in the Knight lab. “We now also have a potential connection to migraines, though it remains to be seen whether these bacteria are a cause or result of migraines, or are indirectly linked in some other way.”
The researchers’ next steps are to look at more defined groups of patients and to separate them into different groups based on the types of migraines they experience. They then believe they will be able to determine if the oral microbes actually express those nitrate-reducing genes and how they may correlate with migraine status.