People who suffer from migraines often know which things will trigger an attack and do their best to avoid them. Nitrates in foods such as chocolate, red wines and processed meats are common triggers, but it has been unclear why some people are more susceptible to getting migraines from them than others. A recent report suggests bacteria from your mouth microbiome may be responsible.

The role of nitrates in migraines stems from the observation that more than 80 percent of heart patients taking medications containing nitrates report having severe headaches. Migraines induced by nitrates fall into two categories, the first are immediate, developing within an hour of taking the nitrate containing medications. The second group of migraines has a delayed onset occurring 3 to 6 hours later and is generally more severe and occurs more often in patients with a family history of migraines.

Research has suggested immediate migraines are associated with vasodilation by nitric oxide while delayed migraines are caused by the release of other molecules. When nitrates are ingested, enzymes present in mouth bacteria — not human cells — can convert ingested nitrate to nitrite. Nitrite is further metabolized by human enzymes to nitric oxide. Nitric oxide is a vasodilator that expands blood vessels in the brain and scalp leading to a migraine.

In the U.S., about 16 percent of those ages 18 or older suffer from migraines. Headaches are most common in women ages 18 to 44. About 14 million people suffer migraines on a nearly daily basis. Migraines are more than just bad headaches; they include a constellation of neurological symptoms including throbbing recurring pain usually on one side of the head but can occur on both. Attacks often include one or more additional symptoms including visual disturbances, nausea, vomiting, dizziness, sensitivity to sound, light, touch and smell and tingling or numbness in extremities or the face. Migraines can last from 4 to 72 torturous hours and can be debilitating.

In this new study, scientists examined the genomes of bacteria present in 2,200 people. They divided them into two groups, those that suffered from migraines and those that didn’t. They then characterized the bacterial populations from stool and oral samples for the abundance of bacteria with the genes coding for enzymes required to metabolize nitrates to nitrites. There were dramatically higher levels of these bacteria in the oral samples from people that suffered from migraines. Four types of bacteria capable of metabolizing nitrate were common in oral samples of migraine sufferers, Pseudomonas, streptococci, Rothia mocilaginosa and Hemophilus parainfluenza. This represents the first link between oral bacteria that metabolize nitrates and migraines.

Further studies with larger populations will try to confirm if diet and the types of nitrate processing bacteria are linked to migraines. It would not be surprising if these findings are confirmed that oral probiotic treatments could be developed to alter the oral microbiome to reduce the populations of bacteria that process nitrates into the migraine causing nitric oxide. Who knew the bacteria that live in your mouth could influence your quality of life?

Medical Discovery News is a weekly radio and print broadcast highlighting medical and scientific breakthroughs hosted by professor emeritus Norbert Herzog and professor David Niesel, biomedical scientists at the University of Texas Medical Branch at Galveston. Learn more at

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