- Nitrate reducing microbes are normally present
in our oral cavities and gut.
- They promote our heart
health by increasing blood flow to the heart and reducing blood pressure.
- If found in higher levels than normal, they may cause
Higher levels of nitrate reducing bacteria in
the oral cavity may cause migraine headaches, rules a recent study at the University of California San Diego School of Medicine (UC San
Aim of the Study
‘Nitrate reducing bacteria that normally occur in the mouth and gut may be good for cardiovascular health, but can cause migraines if found in higher amounts.’
The researchers embarked on the study, based on the assumption that since certain foods were known to trigger
migraines, the headaches might be related to the microbial population in their
"There is this idea out there that certain foods trigger
migraines--chocolate, wine, and especially foods containing nitrates,"
says Antonio Gonzalez, a programmer analyst in the laboratory of Rob Knight at
UC San Diego, and lead author on the study. "We thought that perhaps there
was a connection between someone's microbiome and what they were eating."
Details and Results
of the Study
Gonzalez and his colleague Embriette Hyde sequenced bacteria found in
oral cavity samples from 172 participants, and 1,996 fecal samples from healthy
participants. The participants were earlier asked to complete surveys asking
whether they suffered from migraine
The results of the sequencing indicated to them the qualitative and
quantitative differences in the bacterial population between migraine sufferers
and those who did not. With regards to bacterial
the investigators did not find any significant differences in the fecal or oral samples
of migraineurs and non-migraineurs
Additionally, they employed a bioinformatic tool termed PICRUS to
analyze variations in genes that might occur in the two different sets of
samples, as per the bacterial species present. They detected a slight, but statistically significant
increase in the amount of genes that encoded nitrate, nitrite and nitric oxide
reductases in the fecal samples of migraine sufferers. In the oral samples,
these genes were significantly much higher in persons suffering from migraine
"We know for a fact the nitrate-reducing bacteria are found in the
oral cavity," says Hyde, who is the project manager for the American Gut
Project in the Knight laboratory. "We definitely think this pathway is
advantageous to cardiovascular health, but now we have a potential connection
to migraines as well."
How Nitrates Cause
Many persons, who suffer from migraine headaches have noticed a link
between consuming nitrates and their severe headaches. Patients with heart
disease, who take nitrates for chest pain or congestive heart failure report severe headaches as a side effect.
The authors of the study feel that we may have a mutually beneficial
symbiotic relationship with bacteria in our oral cavities, which do promote our
cardiovascular health. But in some people, an excess of nitrate-reducing
bacteria in the mouth could also lead to migraines, rules the study.
Nitrates, occurring in certain foods such as processed meats, green
leafy vegetables, and in certain medicines, are reduced to nitrites by microbes
found in the mouth. When circulating in the blood, these nitrites become
converted to nitric oxide (NO) under certain conditions. Nitric oxide is a powerful vasodilator
that promotes cardiovascular
health by increasing coronary blood flow and reducing blood pressure.
However, nitrates also cause
vasodilation of the blood vessels supplying the brain, which may be responsible
for the severe headaches
. Vasoconstricting agents such as ergotamine are
generally administered for relief from migraine headaches.
Future Research Plans
Gonzalez and Hyde say that they plan
to study more well-defined groups of patients, segregated on the basis of the
different types of migraines
. They could then determine if the microbes in
their oral cavities actually expressed nitrate-reducing genes, estimate levels
of their circulating NO and study how it correlates with their migraine status.
Perhaps far into the
future, Gonzalez says, "We will have a magical probiotic mouthwash for
everyone that helps your cardiovascular health without giving you
migraines." But for now, he says, "If you suspect that nitrates are
causing you migraines, you should try to avoid them in your diet."