The connections between different parts of the human body are full of surprises, but here is one you may not have considered: Can one thing that causes dandruff on the head also contribute to your digestive problems?
It is a mystery that scientists are trying to unravel with research on fungi living in your gut. While the bacteria that colonize, the intestines have been a scientific focus for more than a decade, the fungi begin to pay more attention.
These studies have already revealed striking connections between fungi and several chronic diseases, including Crohn's disease and ulcerative colitis. As is typical of medical science, a simple explanation (A causes B, which can be cured by C) is unlikely.
"It is a very exciting science to be involved in," said David Underhill, research chair for inflammatory bowel disease at Cedars-Sinai Medical Center in Los Angeles. "I think over the next five years, certainly 10 years, that we will develop a very different understanding of this area."
Dr. Underhills team examines the association between fungi in the gut and inflammatory bowel diseases such as Crohn's.
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Scientists first became interested in studying the microbiome, as advances in DNA technology made it easier to identify microorganisms in and on the human body. Previous work, Dr. Underhill, primarily focused on bacteria, because there are far more of them in our bodies compared to other forms of organisms.
There are trillions of bacteria in the digestive tract, and as many as 100 different species. Mushroom numbers in the hundreds of thousands, with only a handful of different species. For years, fungi were scientifically short-lived.
Now, with our understanding of the better established bacterial microbiome, scientists have pointed out fungi what some call mycobiome. It has quickly become apparent that these organisms play a separate role in our health.
A fungus in the center of Dr. Underhills research is Malassezia. Although its name may be unknown, you are currently covered by it.
The fungus is ubiquitous on a healthy human body; It colonizes the skin shortly after birth. For some people, Malassezia creates scalp irritation that causes dandruff.
But it also comes up in our bodies along the digestive tract. Recently, Dr. Underhill and his colleagues a study in the journal Cell Host & Microbe, suggesting a link between Malassezia in the gut and Crohn's disease.
People with Crohn's had high concentrations of Malassezia on their intestinal walls, while healthy patients had almost none. The researchers then found that simply adding this type of fungus to the intestines – at least in mice – was enough to aggravate the inflammation seen in Crohn's.
This work was based on a growing body of evidence linking fungi with inflammatory bowel diseases. As early as 2010, researchers reported that antifungal drugs helped I.B.D. patients go into remission. In 2012, Malassezia was particularly associated with this type of disease.
In 2016, researchers in France published a study showing that fungal populations in humans with intestinal conditions were quite different from those in healthy patients.
"There are small pieces that we put together", said Mathias Lavie-Richard, a microbiologist at the Micalis Institute in France and a co-author of that study.
The race is on to make these connections and add to the growing evidence. The results could benefit hundreds of thousands of people. Crohn's disease, for example, is commonly treated using anti-inflammatory drugs known as TNF inhibitors. But these treatments are only effective for about 60 percent of patients, according to Crohn's and Colitis Foundation.
Drugs are also expensive: The anti-TNF drug Humira can run as much as $ 38,000 a year, depending on the patient's insurance.
The connection between Crohn's and Malassezia allows for yet to be proven – that something as simple as a generic fungicidal substance could give relief: Wipe out the fungus, dry out the inflammation. Dr. Underhill and his colleagues move into clinical trials now, just one of many teams eager to test the idea.
Researchers in Montreal are pursuing a similar clinical trial of treatment beginning as early as summer, according to Martin Laurence, a researcher and creator of The Malassezia Project, who follows the research published on this particular organism.
It is not only inflammatory bowel diseases that have been associated with mycobiome. A study released last year showed that alteration of the intestinal fungal composition of mice exacerbated asthma symptoms. Some early evidence suggests a relationship between fungal infections and prostate cancer.
"The technology improves every year, we get better and better identify organisms and their role in disease and symptom management," says Dr. J. Curtis Nickel, a urologist at Queen's University in Canada.
Dr. Nickel is a co-author of upcoming research that suggests the link between Malassezia and interstitial cystitis, a chronic and painful bladder condition.
He said the next step for many scientists is to investigate how these fungi interact with and be affected by the other organisms living with them.
"I suppose it's an interaction between all the different bacteria, fungi and viruses," says Dr. Nickel. "An unhealthy population of these organisms exacerbates the disease and maybe even – this is the next step – causing it. But boy, we're not there yet."
Although we are far from declaring antifungal a panacea for gut disorders, researchers are optimistic that further research on mycobiome will help solve the mysteries of these inflammatory diseases and may even offer new forms of treatment.
"When you talk about this research for the people who have these diseases, it is like a new light in the dark," said Dr. Lavie-Richard. "It's a new hope."