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Chapter Three

The Problem

The organ is in trouble, and we've been losing it for three generations or more.

Part One

How we broke it

It's not just one thing. Many forces have hollowed out the modern microbiome.

01The fiber gap

The microbiome evolved on a diet rich in the fibers it can ferment. The Western diet is low in them, and the consequence is poor production of the short-chain fatty acids that keep inflammation in check. [→ Sonnenburg 2014]

02Antibiotic overuse

Antibiotics don't only kill the target. A single short course clears out far more than its target, and some common species were still undetectable six months later. [→ Palleja 2018]

03The hygiene hypothesis

The same sterile environments that reduced infectious disease also removed microbial exposures the immune system evolved to depend on. We cleaned up, and cleaned out. [→ Stein 2016]

04Preservatives and emulsifiers

We add preservatives and emulsifiers to help food survive a global supply chain. Many remain untested for microbiome effects, yet studies already show some can change where gut bacteria live and the signals they make. [→ Chassaing 2015]

The fiber gap~5%of Americans meet the recommended daily fiber intake [→ Quagliani 2017]
19705.5%of US births by C-section [→ Placek & Taffel, NCHS]
→
Today~32%of US births by C-section [→ Osterman, NCHS 2024]

C-sections save lives, and for many parents and babies they're medically necessary, that isn't up for debate. But a surgical birth skips the trip through the birth canal that hands a newborn its first microbes [→ Dominguez-Bello 2010]. Some of that inheritance is lost before life even begins.

842outpatient antibiotic prescriptions per 1,000 Americans in one year (2011, CDC data) [→ Hicks 2015]

Antibiotics save lives too, one of medicine's greatest tools. But they're not a catch-all, and they can't tell friend from foe. Each course clears out far more than its target, and repeated use is one of the clearest drivers of a depleted microbiome.

4×higher asthma prevalence in Hutterite (industrial farming) than Amish (traditional farming) children [→ Stein 2016]

This is the hygiene hypothesis. Clean water and washing your hands are lifesavers. No argument. But we kept going: antibacterial everything, soaps that kill 99.9%, the wipe-it-all-down, shower-it-all-off reflex. An immune system that never meets the microbes it evolved alongside doesn't learn restraint. It turns on allergies, asthma, and autoimmunity instead.

Part Two

How deep the loss goes

The damage isn't a single number. It's three things at once: how much is gone, why it keeps getting worse, and what it's connected to.

01 · How much is gone

We carry a fraction of the diversity we used to.

The Hadza of Tanzania and the Yanomami of the Amazon carry microbial diversity modern Americans have mostly lost. Some of what they carry has never been seen in an industrial population. [→ Schnorr 2014, the Hadza study]

02 · Why it keeps getting worse

We pass a depleted microbiome to our children.

Each generation hands down only what it has, starting from a more diminished baseline than the last. In mice kept on a low-fiber diet, the fiber-fermenting microbes that disappeared weren't just gone for those mice. They were gone for their offspring too. That makes this a generational crisis, not a personal failing. [→ Sonnenburg 2016]

03 · What it costs

Lower diversity shows up alongside a long list of chronic conditions.

As diversity falls, the same signature turns up under condition after condition: fewer short-chain-fatty-acid producers, more pro-inflammatory taxa. The shape repeats. What it means is the harder question. [→ Valdes 2018] [→ Manor 2020]

The industrialized microbiota

Low diversity is associated with disease across many major systems.

The depletion, the inheritance, the systemic toll. The Sonnenburg lab at Stanford calls what industrialized populations now carry an industrialized microbiota, and argues that rapid modernization has driven a progressive deterioration of it: a microbial community still compatible with the world we built, and increasingly incompatible with our own biology.

Deep dive on the blogRestoring the Gut's Ecosystem: How Microbiome Diversity Fuels Health Resilience in a Chaotic World

Antibiotics, preservatives, environmental toxins and stress all press on the gut. Why diversity is the buffer.

Neurological

Mood, memory, focus, and sleep

Digestive

Inflammatory and functional gut conditions, and liver health

Immune & autoimmune

Autoimmune conditions, allergy and asthma, and how the body responds to immunotherapy

Metabolic & cardiovascular

Blood-sugar regulation, metabolic health, and cardiovascular risk

A 2017 meta-analysis in Nature Communications (Duvallet et al.) pooled 28 case-control studies across ten diseases and found something more careful than a single culprit: roughly half the bacteria tied to any one disease are tied to others too. A depleted microbiome doesn't cause every chronic disease, and much of what looks disease-specific is a shared response to being unwell [→ Duvallet 2017].

Deep dive on the blogOne Antibiotic Course Can Scar Your Gut Microbiome for Eight Years

A 2026 study of nearly 15,000 adults found a single round of antibiotics can leave a lasting mark on gut microbial diversity. Lit Review Friday.

Part Three

What we stand to lose

Deep dive on the blogThe Canary Is Still Singing: what your microbiome is trying to tell you

The essay this section grew out of: the microbiome as the canary in the coal mine, and what we add to food so it can travel. One person's reading of the literature, written in a louder voice than the pages here.

Our diversity has fallen hard, and the trend line keeps going down. To see where this road ends, look at the extreme case. Scientists learned to raise mice with no microbiome at all: a body with the organ removed entirely. What followed wasn't a mild deficiency. It was collapse, system by system. [→ the five studies, in the references below]

  • 1

    The brain never wired itself correctly. Development stalled: glia failed to mature, and the blood-brain barrier stayed leaky.

  • 2

    Mood chemistry misfired. The microbial signals that shape serotonin and other neurotransmitters never came online the way they should.

  • 3

    The gut stopped doing its most basic job. Without a microbiome, mice absorbed and stored energy from food differently (Bäckhed 2004).

  • 4

    Stress and behavior changed. Across separate studies, germ-free mice showed stronger hormonal stress responses, more movement and less anxiety-like behavior (Sudo 2004; Diaz Heijtz 2011).

  • 5

    Brain gene activity shifted. Germ-free mice showed altered activity in genes involved in signaling within cells and in strengthening connections between neurons (Diaz Heijtz 2011).

These mice are an extreme model. Humans aren't germ-free. But the takeaway is structural: the microbiome is required infrastructure, not decoration.

"We are sitting on this precipice of essentially a clear-cut ecosystem. Just like in restoration ecology, there are no wrong answers. We need to approach this from every angle we have."
Andrea McBeth, ND

Chapter IV

So what do we do?

We can't grow back the bugs we've lost. The question becomes: can we restore the signals the bugs would have made? The next page is the science of restoration, and the case for one tool that can help.

← The MechanismNext: The Solution →

References

  1. 1Sonnenburg ED, Smits SA, Tikhonov M, Higginbottom SK, Wingreen NS, Sonnenburg JL. Nature. 2016. PMID 26762459.
  2. 2Schnorr SL et al. Nature Communications. 2014. PMID 24736369. (Hadza)
  3. 3Clemente JC et al. Science Advances. 2015. PMID 26229982. (Yanomami)
  4. 4Smits SA et al. Science. 2017. PMID 28839072. (Hadza seasonal cycling)
  5. 5Wastyk HC et al. Cell. 2021. PMID 34256014. (Stanford fermented foods)
  6. 6Hicks LA et al. Clin Infect Dis. 2015;60(9):1308–1316. PMID 25747410. (842 outpatient antibiotic prescriptions per 1,000 persons, US, 2011)
  7. 7Placek PJ, Taffel SM. Public Health Rep. 1983;98(4):396–400. PMID 6611827. (cesarean deliveries 5.5% of US deliveries in 1970)
  8. 8Osterman MJK et al. Natl Vital Stat Rep. 2024;73(2):1–56. PMID 38625869. (cesarean delivery rate 32.1% in 2022)
  9. 9Sonnenburg ED, Sonnenburg JL. Cell Metab. 2014;20(5):779–786. PMID 25156449. (microbiota-accessible carbohydrates)
  10. 10Quagliani D, Felt-Gunderson P. Am J Lifestyle Med. 2017;11(1):80–85. PMID 30202317. (about 5% of Americans meet fiber recommendations)
  11. 11Palleja A et al. Nat Microbiol. 2018;3(11):1255–1265. PMID 30349083. (recovery after a four-day antibiotic course)
  12. 12Dominguez-Bello MG et al. Proc Natl Acad Sci U S A. 2010;107(26):11971–11975. PMID 20566857. (delivery mode and the newborn microbiota)
  13. 13Bäckhed F et al. Proc Natl Acad Sci U S A. 2004;101(44):15718–15723. PMID 15505215. (gut microbiota regulates fat storage, germ-free mice)
  14. 14Chassaing B et al. Nature. 2015;519(7541):92–96. PMID 25731162. (dietary emulsifiers, mice)
  15. 15Valdes AM, Walter J, Segal E, Spector TD. BMJ. 2018;361:k2179. PMID 29899036. (lower diversity across chronic conditions, review)
  16. 16Manor O et al. Nat Commun. 2020;11(1):5206. PMID 33060586. (health and disease markers vs gut microbiome composition, n=3,400)
  17. 17Duvallet C, Gibbons SM, Gurry T, Irizarry RA, Alm EJ. Nat Commun. 2017;8(1):1784. PMID 29209090.
  18. 18Sonnenburg ED, Sonnenburg JL. Nat Rev Microbiol. 2019;17(6):383–390. PMID 31089293. (industrialized microbiota)
  19. 19Yano JM et al. Cell. 2015;161(2):264–276. PMID 25860609. (spore-forming bacteria and gut serotonin)
  20. 20Sudo N et al. J Physiol. 2004;558(Pt 1):263–275. PMID 15133062. (germ-free mice, stress axis)
  21. 21Diaz Heijtz R et al. Proc Natl Acad Sci USA. 2011;108(7):3047–3052. PMID 21282636. (germ-free mice, brain development and behavior)
  22. 22Braniste V et al. Sci Transl Med. 2014;6(263):263ra158. PMID 25411471. (germ-free mice, blood-brain barrier)
  23. 23Erny D et al. Nat Neurosci. 2015;18(7):965–977. PMID 26030851. (germ-free mice, microglia maturation)
  24. 24Stein MM et al. N Engl J Med. 2016;375(5):411–421. PMID 27518660. (Amish vs. Hutterite farm children & asthma)

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. ThaenaBiotic® is a dietary supplement. The research summarized on these pages describes the science behind our approach; it does not describe what ThaenaBiotic does for any person or condition.