What causes multiple sclerosis has been a question for centuries. One area of research that explores possible causes of MS is the hygiene hypothesis. This hypothesis suggests that the natural development of the immune system may be hindered by a lack of exposure to infectious agents and bacteria.
Tens of thousands of bacterial species exist in the human body – outnumbering other cells by ten to one. We’ve always known that bacteria can have a negative impact on our health, but in fact scientists are learning that some bacteria may also have a positive impact. Over the past decade, there has been increasing interest in the beneficial role that bacteria may play in chronic illnesses, including MS.
One general study in this realm of research is the Human Microbiome Project which launched in 2007 to map the microorganisms, including bacteria, which are found in both healthy and diseased people. The project has created a reference database and laid out the boundaries of normal microbial variation in humans.
Helicobacter pylori (H. pylori) is a bacteria that resides in the stomach. H. pylori was once found in the stomachs of nearly every person in the world. It remains prevalent in developing countries, but due to increased hygiene and use of antibiotics, its presence has significantly decreased over the past century and it is found in just five percent of children born in the United States.
One study, not specifically focused on MS, conducted in 2007 by scientists at New York University, involved more than 7,500 adults found that those who did not have H. pylori in their stomach were more likely to have had asthma as kids than those who did. Research has also shown that the absence of some types of bacteria may contribute to Crohn’s disease, obesity and other chronic illnesses.
Another recent study, published in the Journal of Neurology, Neurosurgery, and Psychiatry, evaluated the association between H. pylori, and MS. This study involved 550 MS patients, mostly female (75%) with an average age of 47 years, along with 299 sex- and age-matched healthy controls. The study, which is the largest ever to evaluate this association, showed that this particular bacteria is significantly lower in women with MS than in female healthy controls, suggesting that H. pylori, may have a protective effect. The same association was not found in men.
The results of this most recent H. pylori study lends some support to the hygiene hypothesis. However, the possible connections between our immune system, bacteria, and chronic diseases are complex. In a 2012 interview with The New Yorker magazine, Dr. Martin Blaser, the chairman of the Department of Medicine at New York University School of Medicine, explained what research on H. pylori demonstrates about these complexities: “Drugs [antibiotics] have saved countless lives, and it is very important that we not lose sight of that fact. Whenever they are used, though, there is collateral damage. This is just our best understood example…There are specific circumstances which H. pylori can cause harm, but without it we are in real trouble.”
While the recent study supports the hygiene hypothesis, it is too early to draw conclusions about potential protective effects of the H. pylori bacteria to lower MS risk. However, there is ever-increasing energy around exploring these questions about potential connections between bacteria, our immune systems, and chronic diseases like MS further and this research will be important for all of us to follow.