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A stomach bacterium causes Parkinson's disease
Last reviewed: 30.06.2025
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Helicobacter pylori, which lives in the stomachs of almost half of the earth's inhabitants, modifies cholesterol in such a way that it causes the degeneration of dopamine-producing cells in the brain - and this, unfortunately, leads to the development of Parkinson's disease.
The gastrointestinal bacterium Helicobacter pylori, with all its positive qualities, is a rather dangerous symbiont: it is believed that it is one of the main causes of peptic ulcer disease. Moreover, if we believe microbiologists from the Center for Health Research at the University of Louisiana (USA), the danger of this bacterium is even underestimated, and seriously. As experiments by Americans have shown, Helicobacter can provoke Parkinson's disease.
Parkinsonism is a severe neurodegenerative disease that is associated with the destruction of special cells in the brain that produce the neurotransmitter dopamine, which is primarily manifested in uncontrolled movements of the patient, tremors, etc. Every year in the United States alone, about 60 thousand new cases of Parkinson's disease are diagnosed. There was evidence that this disorder occurs with a higher probability in people suffering from or having had a stomach ulcer and infected with Helicobacter pylori, but to this day there has been no reliable evidence in favor of a connection between this bacterium and Parkinsonism.
And then, at the American Society for Microbiology meeting on May 22, it was reported that Helicobacter was causing Parkinson's disease in mice. Middle-aged animals began to exhibit uncontrolled movements several months after they were infected with the bacteria; they also had a decrease in the number of dopamine-producing cells in the motor lobes of the brain, further indicating the development of Parkinsonism. (Young mice were not affected by H. pylori infection.)
It turns out that the bacteria don’t even have to be alive to cause Parkinson’s: the same symptoms appeared in animals fed dead Helicobacter bacteria. This led the researchers to take a closer look at the biochemistry of H. pylori. The microorganism can’t produce cholesterol itself, so it borrows it from its host, but modifies it slightly by adding a carbohydrate residue. The resulting molecule resembles a toxin from a tropical cycad. This tree’s toxin causes symptoms of amyotrophic lateral sclerosis and Parkinson’s disease.
It turned out that modified cholesterol synthesized by Helicobacter, in itself (in pure form) is capable of causing symptoms of Parkinsonism in mice.
H. pylori lives in the stomach of about half of the world's population. But even if we try to expel it from all carriers with colossal efforts, it is not very clear what to do with the negative effects that will inevitably appear in the absence of this bacterium in the human body. Although Helicobacter provokes peptic ulcer disease and even stomach cancer, at the same time it protects us from some allergies, asthma, esophageal cancer and certain disorders associated with acid balance. Obviously, it is easier to learn to soften the disposition of this peculiar symbiont than to take any decisive and unambiguous measures against it.
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