For years I’ve been wondering what is going wrong with our health. The legion of diseases that have moved from rare to epidemic in one century is staggering: obesity, diabetes, autism spectrum disorders, asthma, inflammatory bowel disease, food allergies, lupus, Crohn’s disease, Alzheimer’s, cancer, and depression. To name a few. Since these diseases aren’t transmitted from person to person directly, they are collectively referred to as non-communicable diseases, or NCDs.

Some sources estimate over 50% of Americans suffer from an NCD. This level of illness makes a mockery of actuarial tables, leaving insurance companies in a state of fear even without government shenanigans. You have not imagined the growing burden of health care cost being shifted to you.

I’ve been prepping for a new job in the gig economy that involves writing about the human microbiome, or MB. Current science–and this is new science in the 21st century, so new that my spellchecker keeps flagging the term-posits widespread changes in the makeup of the individual MB as the source for our NCD explosion.

The human MB refers to the trillions of microorganisms that live on and in us. They are hard to count, and so are cells, but there are probably as many or more microbes than cells in a person. Of course microbes are much smaller. Once thought to be mostly benign and occasionally pernicious, they now appear to play critical roles in our immune systems, diets, blood chemistry, and moods.

Until less than 100 years ago, the MB was seeded in the birth canal, then supplemented through breast feeding. The MB maintained healthy diversity lifelong through exposure to microbes in the soil, water, and air, as well as from other animals. The type of MB that keeps you healthy likes to eat plant fiber, as well as some fermented food; interestingly, every human culture has created an appropriate fermented food, including sauerkraut, kimchi, and sourdough.

In the late twentieth century, a perfect storm of technological breakthroughs and changing cultural mores coincidentally targeted the healthy MB before scientists even perceived its existence. Temperature-controlled houses and workspaces, as well as a rise in desk work, led to us spend more time indoors. Personal hygiene and home cleaning standards and products reduced the diversity of the microbes remaining. Fiber-light processed foods became ubiquitous; for the most part, fermented foods with live microbes weren’t offered in processed form. Caesarean births rose, and breast-feeding rates fell. And with the best intentions, when we found antibiotics could cure very sick people, we started also giving them to not very sick people, then to people who might get sick, then to animals we were raising to eat, which spread them to our rivers and fields.

Some babies never established a good MB, or lost it early to childhood diseases treated with antibiotics. Many adults stopped replenishing our MBs with outdoor exposure, or stopped feeding them healthy food. Some MBs are unhealthy. The processed-food loving, low-diversity MB is not interested in building up our immune systems, and actively works to keep us both overweight and oversugared.

This is a very large change, a large idea to get used to, an idea with massive implications. I’d say it’s right up there with Earth is not the center of the solar system. Unsurprisingly, some clinicians are resisting it, and you may as well, especially if you’re a boomer. After all, we lived through the era of science saying smoking was healthy, and the introduction of the really-bad-for-you food pyramid.

But something is causing this mess, and I think this is the most hopeful theory we’ve had in a while. After all, your MB can be altered.

This is a huge topic, and pretty new science. Just like on your kitchen counter, there are good and bad microbes in and on your body, and when you destroy the good ones, the bad ones can take over. This is what has happened in a nutshell. Widespread antibiotics in our medications, food, and environment have weakened the good ones even in small children who are still establishing. Add to this availability of processed foods that are preferred by the bad microbes; work and homes that keep us indoors, away from good-microbe-replenishing soil, wind, and water; cultural cleanliness habits that kill microbes on our bodies and in our homes;