The pain can cause you to vomit or temporarily lose your vision, and usually there’s not much you can do except wait it out.
Though migraines strike about 38 million Americans, their cause is something of a medical mystery. These debilitating headaches can take hours to subside, leaving patients the option of taking pain relievers that may only slightly decrease their symptoms, or daily medication to try to prevent them. Although doctors understand that certain factors can be triggers for migraines—including foods like chocolate, wine, and processed meats—they’ve never been sure why.
Bacteria may be at the heart of the solution to this puzzle. A team of researchers led by scientists from the University of California San Diego (UCSD) School of Medicine analyzed oral and stool samples from roughly 2,200 individuals and found that that those who suffered the most from migraines had higher levels of microbes that alter the nitrates in certain foods into migraine-inducing chemicals. Their work was published in mSystems on Tuesday (Oct. 18).
Trillions of bacteria live throughout our bodies. Just like our bodies extract nutrients from food and extract what we don’t need, these bacteria do too. Sometimes, the waste they create ends up affecting us.
Food like wine, chocolate, processed meats, and even green vegetables contain chemicals called nitrates. These compounds are composed of a nitrogen atom along with three oxygen atoms. Some bacteria that live in our mouths—in particular, Rothia mucilaginosa and Haemophilus parainfluenzae—break down these nitrates for their own fuel. In doing so, they remove one of the oxygen atoms from nitrates, which results in a chemical byproduct called a nitrite. When nitrites enter the bloodstream, they can be converted into nitric oxide (with just one oxygen atom), which has been linked (paywall) to migraines and other kinds of tension headaches.
For their work, researchers from UCSD analyzed microbial DNA collected in the American Gut Project. They looked at 172 oral samples and 1,996 fecal samples, and found that people who get migraines tended to have more bacteria capable turning nitrates into nitrites in both their mouths and their guts.
This works supports the documented connection between nitrate-rich foods and migraine headaches; in theory, migraine sufferers should avoid these foods to avoid migraines. But the team speculates that these microbes may also benefit us by improving our heart health. Patients with heart failure are often prescribed nitrites to regulate their condition, and many of them endure migraines as a side effect.
The UCSD study found a linkage between nitrite-producing bacteria and migraines, but did not confirm the bacteria are a definite cause. Antonio González Peña, a computer scientist at UCSD and lead author of the paper, and his team will next look at the patients with various types of migraines, like aura or retinal, to see if there’s a way to connect specific species of bacteria to these different forms of the common illness. The goal is to eliminate migraines without risking heart health. Ideally, he said in a statement, “we will have a magical probiotic mouthwash for everyone that helps your cardiovascular health without giving you migraines.”