Rising asthma rates may be partly explained by bacterial imbalances in our guts.
In a study published yesterday in the Journal of Infectious Diseases, researchers showed that Heliobacter pylori, an intestinal microbe that co-evolved with humans, appears to protect children from asthma. Asthma rates have nearly doubled in the United States since 1970, and are swelling in the developing world. Underlying the rise is a constellation of causes -- and one of these may be the loss of H. pylori, a vanishing member of the rich bacterial ecosystems in our stomachs. Nearly universal at the advent of modern antibiotics, it's now present in just one-fifth of young Americans. The drop is a boon for people in whom the bacteria would eventually cause stomach problems, but some researchers say the bug is needed to calibrate our immune systems.
"When humans left Africa, they had H. pylori in their stomachs. It was universal. And it's now clear that H. pylori is disappearing. Ulcer diseases and stomach cancers are going away, but new diseases are appearing -- including asthma and related disorders," said study co-author Martin Blaser, a New York University microbiologist. Blaser and NYU colleague Yu Chen analyzed the medical histories and stool samples of more than 7,400 people enrolled in the National Health and Nutrition Examination Survey. After controlling for other variables, they found that the presence of H. pylori was associated with a 25 percent fall in asthma rates among people under 20 years old. The drop was even more significant in H. pylori-positive children aged 3 to 13: They were 59 percent less likely to develop asthma.
Kids with H. pylori were also less likely to have eczema and hay fever -- disorders that often accompany asthma, and likely share the same roots in immune systems that are excessively sensitive to everyday contaminants. Blaser said the bacteria's presence triggers the production of Th17 cells, a type of regulatory cell that determines the body's response to foreign bacteria and pollution. "We use the analogy of flooding: If you build a high enough levee, it doesn't matter how much it rains. But with no levee, there's a flood. The Th17 cells are the levee," said Blaser.
"Embryologically, the lung is derived from gastrointestinal tissue. Our hypothesis is that having enough Th17 cells in childhood sets the threshold for allergic sensitization," he continued. "Children with H. pylori have plenty of these cells, but children without have few of them. That's kind of a smoking gun." There is, however, a positive side to the loss of H. pylori: the bacteria has been linked to stomach ulcers and gastric cancers. Nobody has yet weighed the risks of H. pylori's against its benefits, but Blaser said it may only be the most visible of many intestinal microbes exterminated by seven decades of antibiotics and modern sanitization.
"Organisms we've had inside us for thousands, even millions of years are vanishing. H. pylori is the best example. And when you have an organism with us for a very long time that disappears, there will be consequences," he said. Source: Wired Science.
In a study published yesterday in the Journal of Infectious Diseases, researchers showed that Heliobacter pylori, an intestinal microbe that co-evolved with humans, appears to protect children from asthma. Asthma rates have nearly doubled in the United States since 1970, and are swelling in the developing world. Underlying the rise is a constellation of causes -- and one of these may be the loss of H. pylori, a vanishing member of the rich bacterial ecosystems in our stomachs. Nearly universal at the advent of modern antibiotics, it's now present in just one-fifth of young Americans. The drop is a boon for people in whom the bacteria would eventually cause stomach problems, but some researchers say the bug is needed to calibrate our immune systems.
"When humans left Africa, they had H. pylori in their stomachs. It was universal. And it's now clear that H. pylori is disappearing. Ulcer diseases and stomach cancers are going away, but new diseases are appearing -- including asthma and related disorders," said study co-author Martin Blaser, a New York University microbiologist. Blaser and NYU colleague Yu Chen analyzed the medical histories and stool samples of more than 7,400 people enrolled in the National Health and Nutrition Examination Survey. After controlling for other variables, they found that the presence of H. pylori was associated with a 25 percent fall in asthma rates among people under 20 years old. The drop was even more significant in H. pylori-positive children aged 3 to 13: They were 59 percent less likely to develop asthma.Kids with H. pylori were also less likely to have eczema and hay fever -- disorders that often accompany asthma, and likely share the same roots in immune systems that are excessively sensitive to everyday contaminants. Blaser said the bacteria's presence triggers the production of Th17 cells, a type of regulatory cell that determines the body's response to foreign bacteria and pollution. "We use the analogy of flooding: If you build a high enough levee, it doesn't matter how much it rains. But with no levee, there's a flood. The Th17 cells are the levee," said Blaser.
"Embryologically, the lung is derived from gastrointestinal tissue. Our hypothesis is that having enough Th17 cells in childhood sets the threshold for allergic sensitization," he continued. "Children with H. pylori have plenty of these cells, but children without have few of them. That's kind of a smoking gun." There is, however, a positive side to the loss of H. pylori: the bacteria has been linked to stomach ulcers and gastric cancers. Nobody has yet weighed the risks of H. pylori's against its benefits, but Blaser said it may only be the most visible of many intestinal microbes exterminated by seven decades of antibiotics and modern sanitization.
"Organisms we've had inside us for thousands, even millions of years are vanishing. H. pylori is the best example. And when you have an organism with us for a very long time that disappears, there will be consequences," he said. Source: Wired Science.
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