Helicobacter Pylori
Helicobacter pylori, a bacterium, is fast vanishing from the rich world.
Martin Blaser has linked the bug’s disappearance with increased levels of obesity, cancer of the esophagus and, as of last month, asthma (see “Does Helicobacter pylori protect against asthma and allergy?.”)
H. pylori’s relatives have probably been living in mammalian stomachs since the mammals began, some 150m years ago. It, itself, has been around for at least 60,000 years and until about 50 years ago it infected 70-80% of the human population. Now, as a consequence of the routine use of antibiotics and improved hygiene, only 5% of American children have it.
H. pylori helps to regulate stomach-acid levels. If the stomach becomes too acid, the bug may produce cag, which lowers the acid level. But cag is toxic to the stomach lining, and can provoke ulcers and cancers.
Antibiotics may be used as an anti-ulcer treatment but this kills H. pylori’s homeostatic effect and allows the strength of the stomach acid to rise chronically, causing gastroesophageal reflux disease (which feels like bad heartburn). Over time, the damage the excess acid does to the walls of the esophagus may cause cancer.
When Blaser analysed the National Health and Nutrition Examination Survey database, he found that US children between the ages of 3 and 13 who are infected with H. pylori are 60% less likely to have asthma than their uninfected contemporaries.
H. pylori also has an effect on two of the hormones that control appetite — ghrelin, which makes you feel hungry, and leptin, which does the opposite. People without H. pylori produce more ghrelin than those with.
“The twists and turns of fate,” The Economist