What do germs, dirt and a blind, blood-sucking intestinal worm have in common?
Our instincts may tell us to avoid each of these things to protect our health, but research shows that microbes -- microscopic organisms such as bacteria, fungi and viruses that live in our bodies and are too small to see with the naked eye -- and dirt are crucial for our well-being. Recent studies also show promise that the intestinal worm, also known as a hookworm, may eventually help fight asthma and other chronic conditions.
With the advent of the modern toilet and sewage system in the early 1900s and subsequent advances in developing antibacterial soaps and other strong cleaning products, living conditions in the U.S. are much more hygienic than they were for previous generations. And that's a problem, some germ experts say.
"I'm a sound believer that we're too clean of a society," says Dr. Christopher Carpenter, section head of infectious diseases and international medicine at Beaumont Hospital in Royal Oak, Michigan. "Our fear of germs has pushed us too far into trying to keep everything safe and sterile. That extreme is harming us more than it's helping us."
"We are getting far too sterile," adds Kiran Krishnan, a microbiologist and chief scientific officer for Microbiome Lab in Glenview, Illinois. "Exposure to microbes is an essential part of being human. Most of our immune system is comprised of tissue that requires activation by the microbes we're exposed to. The immune system requires the presence of friendly bacteria to regulate its functions. Think of the immune system as an army, with tanks and missiles but no general to lead them. That's the role friendly microbes play in your body; they're the general." The vast majority of microbes, 97 to 99 percent, are benign or beneficial, and they are the best protection to fight pathogenic microorganisms, Krishnan says.
Carpenter believes in the hygiene hypothesis, which holds that people who grow up in areas with high levels of sanitation lack normal evolutionary exposure to microbes, pollen and other microscopic things in the environment. The lack of that exposure negatively affects the development of their immune system, according to the hypothesis.
Carpenter and Krishnan say they aren't against good hygiene. Instead, they say that modern Western society has gone overboard with deploying antibacterial soap and germ-killing cleaning products, which indiscriminately kill germs -- including good bacteria that help maintain a strong and diverse microbiome. Everyone has a microbiome, a collection of about 100 trillion bacterial cells, primarily in the gastrointestinal tract. "The more diverse your microbiome is, the healthier you are," Krishnan says.
A healthy, diverse microbiome boosts one's immune system. Plus, a study published in 2015 in Occupational & Environmental Medicine, an international peer-reviewed journal, studied the effects of the use of bleach -- effective in killing germs -- in the homes of more than 9,000 kids ages 6 to 12 in Spain, the Netherlands and Finland. The incidence of infections such as the flu, tonsillitis, sinusitis, bronchitis and pneumonia was more prevalent in the homes where bleach was used, the study found. In a 2015 study published in the journal Science Translational Medicine, researchers looked at stool samples from 319 infants and found that the 22 who were most at risk of asthma had much lower amounts of four specific bacterial species than the children who were not at risk of asthma. This suggests the presence of those four microbes early in life could be connected to protecting kids from asthma.
The Benefits of Dirt
Your mom probably scolded you for playing in the dirt, but doing so may be healthy, according to a 2016 study published in the New England Journal of Medicine. Researchers studied two Christian farming groups: Amish schoolchildren and Hutterite kids. The Amish practice traditional farming, using hand-held tools, while the Hutterites use modern farm equipment, such as tractors and front loaders. Compared to the Hutterite kids, the Amish group had a far lower prevalence of asthma, the study found. Researchers tested the blood of the kids in both groups and found the Amish children had significantly more white blood cells, which are key to fighting infections. One study author theorized the Amish kids had more white blood cells because they had a greater exposure to microbes, which boosted their immune system.
Intestinal Worms and Disease
The New World hookworm is an intestinal worm found in tropical climates such as Central America and the West Indies, as opposed to the Old World hookworm, native to parts of Europe, India and other regions. It is long and thin and has fangs it uses to dig into the intestinal wall of the person it is living in to consume his or her blood. And it could one day help fight asthma. A 2016 study in Science Translational Medicine found the hookworm produced a protein that helped ease asthma symptoms in mice. A separate 2016 study in the journal Science found that feeding intestinal worms to mice boosted the mucus-producing cells in their intestines, which helped them fight Crohn's disease.
This research appears promising, but large clinical studies involving humans are needed to determine whether intestinal worms, which are unusual in people in developed countries like the U.S., can help fight human diseases, says Dr. Jonathan Jacobs, clinical director of medicine in the division of digestive diseases at David Geffen School of Medicine at UCLA. If they can, researchers could extract the disease-fighting material from worms and provide it to humans in pill or liquid form, Krishnan says.
Welcome Those Microbes
You don't have to live or work on a farm to boost the diversity of your microbiome. Experts suggests these strategies:
Don't be afraid of microbes. A small percentage of microbes -- such as Clostridium difficile, a bacteria that can cause severe diarrhea in people on antibiotics -- can be harmful if your microbiome is not diverse enough. You won't know how diverse yours is unless you participate in a clinical study testing your colonic flora, the collection of microorganisms inside the digestive tract, Carpenter says. However, you can sign up with the American Gut Project, run by researchers at UC San Diego, to send in a stool sample for an analysis to identify the various microbes found in your sample. "They can give you an idea of the type of microbes in your intestines, which will give you an idea of the diversity," Krishnan says.
There are simple ways to boost your microbe diversity, Krishnan says. "Almost everywhere we go in the environment, from parks to woods to rivers, we come into contact with microbes." They can enter our respiratory system, our digestive system or just hang on our skin."
Reduce your use of chlorine-based cleaners. Such products can help sterilize surfaces, but living in a sterilized environment can be bad for your microbiome. "You actually want to build a healthy microbial environment in your house," Krishnan says. "You don't want to live in a sterilized house."
Unless you're in a hospital and need to avoid infection, skip the antibacterial soap, which kills all microbes indiscriminately, including the benign and good ones, Carpenter advises. Regular cleaners and soaps, citrus-based cleaning products and mixtures of lemon juice and water are typically fine alternatives, the microbiologist says, because they'll protect you from infection but won't kill the microbes on your hands.
Have closer interactions with people. "We don't hug and kiss as much as we should," Krishnan says. "We need closer interactions with other humans, because that exchange of microbes is important for your immune system."
Such interactions can expose you to a greater variety of microbes, boosting the diversity of your microbiome -- and potentially keeping you healthier.
Ruben Castaneda is a Health & Wellness reporter at U.S. News. He previously covered the crime beat in Washington, D.C. and state and federal courts in suburban Maryland, and he's the author of the book "S Street Rising: Crack, Murder and Redemption in D.C." You can follow him on Twitter, connect with him at LinkedIn or email him at firstname.lastname@example.org.