Most people only think about their gut when something goes wrong — bloating, discomfort, irregularity after a bad meal. But the research paints a far more significant picture. Your gut microbiome is linked to your immune function, your brain chemistry, your hormonal balance, your cardiovascular health, and your risk of developing nearly every major chronic disease. This week, we dig into what a healthy gut is actually doing, what modern life is doing to it, and the practical steps worth taking. But first, we filtered the noise — here's what's worth knowing this week.
THE FILTER
Receipts Are Covered in BPA — And Your Hand Lotion Is Making It Worse — Thermal receipt paper — the kind printed at every checkout counter — is coated in Bisphenol A (BPA), the same endocrine-disrupting chemical found in plastics and food can linings. In a recent appearance on The Diary of a CEO, Dr. Rhonda Patrick (@foundmyfitness) highlighted a particularly alarming finding: if you have any kind of lotion, cream, or hand sanitizer on your skin when you touch a receipt, BPA absorption increases by up to 100-fold, because BPA is fat-soluble and these products carry it directly into the bloodstream. Studies have shown that cashiers who handle receipts daily have measurably elevated BPA levels in their urine. BPA is a well-established endocrine disruptor — meaning it mimics estrogen and interferes with hormonal function, metabolism, reproduction, and development. The fix is simple: opt for digital receipts, and if you handle them regularly, use nitrile gloves — not latex, which does not block BPA absorption. [Diary of a CEO / @foundmyfitness, March 2026]
Your Workout Clothes May Be Exposing You to BPA — In addition to receipts, BPA has been found in another unlikely place: the athletic clothing most people wear daily. Independent testing by the Center for Environmental Health (CEH) found BPA levels in popular sports bras, leggings, and athletic shirts at up to 40 times the maximum safe exposure limit set by California law — and the finding applied to major brands including Nike, Athleta, Patagonia, Adidas, and others. The concern is not just the presence of the chemical but the conditions under which it is absorbed. During exercise, skin temperature rises, pores dilate, and sweat acts as a solvent — all of which increase the rate of chemical transfer from fabric to skin. The CEH recommends changing out of synthetic activewear promptly after exercise, and choosing clothing certified under OEKO-TEX or made from natural fabrics like organic cotton. [Center for Environmental Health]
The Striver's Curse — Why Achievement Doesn't Deliver the Happiness You Expect — Harvard professor and behavioral scientist Dr. Arthur Brooks has spent years studying why high achievers often feel empty despite reaching the goals they spent years pursuing. In a recent appearance on FoundMyFitness, Brooks explained what he calls the "striver's curse" — the brain is wired to reward the pursuit of a goal, not the achievement of it. Once you get there, the neurochemical reward fades rapidly, the target simply resets higher, and the feeling of satisfaction you anticipated never fully arrives. This is the hedonic treadmill at work — a feature of brain biology, not a personal failing. Most “strivers” obsess over increasing what they have. His research suggests that reducing what you want is the most reliable path to lasting fulfillment. It is an insight that cuts against almost everything modern culture tells ambitious people about success. [Dr. Arthur Brooks / FoundMyFitness, March 2026]
Deep Dive
Your Gut Is Running More Than Your Digestion
Most people think about gut health when something goes wrong — when they're bloated, irregular, or uncomfortable after a meal. But the research tells a different story. Your gut isn't just a digestive organ. It is one of the most consequential systems in your body, with direct lines of influence over your immune function, hormonal balance, brain chemistry, cardiovascular health, and your risk of developing nearly every major chronic disease.
The gut microbiome — the ecosystem of trillions of bacteria, fungi, and other microorganisms living in your digestive tract — is now one of the most actively researched areas in medicine. A 2022 review published in Nature described gut dysbiosis, an imbalance in this microbial community, as associated with major causes of morbidity and mortality ranging from cardiovascular disease and colorectal cancer to diabetes, chronic kidney disease, and neurological disorders. [1] The question is no longer whether the gut matters. It is whether you are doing anything about it.
What a Healthy Gut Is Actually Doing
A well-functioning gut microbiome performs several critical jobs simultaneously.
It trains and regulates your immune system. Approximately 70% of the body's immune tissue lives in or around the gut lining. The microbiome helps determine which immune responses get triggered and which get suppressed — a miscalibration here is central to autoimmune disease. It produces short-chain fatty acids (SCFAs) like butyrate, the primary energy source for the cells lining your colon, which also regulate inflammation and maintain the integrity of the intestinal barrier. And it communicates directly with your brain via the gut-brain axis — a bidirectional signaling network involving the vagus nerve, the enteric nervous system, and microbial metabolites that influence the production of serotonin, dopamine, and GABA. Roughly 90% of the body's serotonin is produced in the gut. Serotonin is referred to as the “feel good” chemical because it modulates anxiety, stabilizes mood, and promotes feelings of well-being.
Microbial diversity — the number and variety of different bacterial species present — is the most widely cited marker of a healthy microbiome. Lower diversity is consistently associated with obesity, metabolic disease, inflammatory bowel disease, neurodegenerative disorders, and cancer. Higher diversity is associated with resilience, immune competence, and better health outcomes across the lifespan.
What Disrupts the Gut — and What Follows
The modern lifestyle is, in a fairly direct sense, hostile to the gut microbiome. Several well-documented factors drive dysbiosis:
Diet is the most powerful lever. Ultra-processed foods — which now account for the majority of calories consumed in Western diets — are low in fiber, high in additives, emulsifiers, and artificial sweeteners, and actively deplete microbial diversity. Emulsifiers in particular have been shown to degrade the protective mucus layer lining the gut. A diet chronically low in fiber starves the SCFA-producing bacteria that keep the intestinal barrier intact.
Sleep disruption directly affects microbial composition. A 2025 review in Frontiers in Microbiology found that chronic sleep disruption reduces the abundance of Faecalibacterium prausnitzii, one of the most important anti-inflammatory bacterial species in the human gut. [3] The relationship is bidirectional — a disrupted microbiome also impairs sleep quality — creating a feedback loop that compounds over time.
Chronic stress elevates cortisol, which alters gut motility, reduces blood flow to the intestinal lining, and shifts microbial composition toward pro-inflammatory species. The HPA axis — the body's primary stress response system — has direct receptors in the gut, and new 2025 research confirmed that gut microbes actively regulate diurnal cortisol rhythms. When the microbiome is disrupted, stress hormone regulation breaks down.
Antibiotic overuse is one of the most significant but underappreciated threats. A single course of broad-spectrum antibiotics can eliminate hundreds of bacterial species, and recovery to baseline diversity — if it happens at all — can take months to years. Repeated courses compound the damage.
Alcohol and NSAIDs (non-steroidal anti-inflammatory drugs like ibuprofen and aspirin) both directly increase intestinal permeability when used chronically, contributing to what is often called "leaky gut".
When the Barrier Breaks Down
The intestinal barrier is a single-cell-thick lining that separates the contents of your gut from your bloodstream. When this barrier is intact, it selectively allows nutrients and water through while keeping bacteria, toxins, and undigested food particles out. When it is compromised — through dysbiosis, chronic inflammation, diet, or stress — that selectivity breaks down.
A 2024 study from Jagiellonian University Medical College published in Clinical and Experimental Medicine described what follows when the barrier is damaged: dysbiosis deepens, microorganisms translocate into intestinal tissue, the immune system mounts a response, and chronic systemic inflammation develops. [2] The review documented associations between increased intestinal permeability and a variety of conditions — IBD, celiac disease, rheumatoid arthritis, ankylosing spondylitis, lupus, neurodegenerative conditions, type 2 diabetes, and obesity. It is important to note that the causal direction in many of these associations remains under investigation — in some cases, the disease may cause the permeability rather than the reverse. What is clear is that they are deeply intertwined.
The gut also communicates downstream through a series of established axes (bidirectional communication networks). Dysbiosis has been linked to cardiovascular disease via the gut-heart axis, to non-alcoholic fatty liver disease via the gut-liver axis, to depression and cognitive decline via the gut-brain axis, and to hormonal dysfunction via the gut-reproductive axis. A 2025 study published in Nature identified imidazole propionate — a metabolite produced by specific gut bacteria — as both a contributor to atherosclerosis and a promising early biomarker of subclinical cardiovascular disease, acting by disrupting insulin signaling and amplifying inflammation. [4]
The gut is not just a digestive organ. It is a signaling hub. And when it is dysregulated, the signal reaches everywhere.
The Path Forward
The gut microbiome is not fixed. It is responsive — to what you eat, how you sleep, how you manage stress, and how you treat your body day to day. The evidence on what moves it in the right direction is increasingly consistent, and the interventions are not complicated. They are mostly the same foundational behaviors that show up across every area of health — applied here with the gut in mind.
ACTIONABLE TAKEAWAYS
1. Prioritize dietary fiber — and diversify your plant sources — Fiber is the primary fuel for SCFA-producing bacteria, and SCFA production is central to intestinal barrier integrity, immune regulation, and anti-inflammatory signaling. Most adults consume well below the recommended 25–38 grams per day. More important than hitting a number is diversity — different fiber types feed different bacterial species. Research suggests aiming to eat 30 or more different plant foods per week across vegetables, fruits, legumes, whole grains, nuts, and seeds. While this may be difficult for many people, the takeaway is that variety matters as much as volume.
2. Add fermented foods to your regular routine — A landmark Stanford study published in Cell found that a diet high in fermented foods — yogurt, kefir, kimchi, sauerkraut, fermented cottage cheese, kombucha — measurably increased gut microbial diversity and reduced 19 inflammatory proteins in the blood, including interleukin-6, which is associated with type 2 diabetes, rheumatoid arthritis, and chronic stress. [5] Every participant in the fermented food group showed a reduction in inflammatory markers. Start with one to two servings per day and build from there. Look for products with live active cultures and no added sugar.
3. Protect your sleep — The gut-sleep relationship is bidirectional and consequential. Chronic sleep disruption measurably depletes anti-inflammatory bacterial species and disrupts cortisol regulation via the gut-brain axis. The same sleep architecture targets from Issue 03 apply here: 7–9 hours, consistent bed and wake times, no caffeine after 2pm, and an environment kept between 65–68°F. Protecting your sleep is protecting your microbiome.
4. Be deliberate about what you put in your gut — Alcohol, chronic NSAID use and a diet heavy in processed foods are among the most modifiable threats to the intestinal barrier and microbial diversity. Limit alcohol consumption and use NSAIDs sparingly. Eat a diet rich in whole foods and vegetables and read nutrition labels to avoid consuming emulsifiers where possible. Common emulsifiers include: soy lecithin, carrageenan, mono- and diglycerides, guar gum and xanthan gum.
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Wellness, filtered.
The Wellness Brew
Sources:
PMC 2022 (Nature, Signal Transduction and Targeted Therapy) — gut-organ axes and dysbiosis overview — Link
PMC 2024 — Jagiellonian University, Clinical and Experimental Medicine — intestinal permeability causes and downstream disease — Link
Frontiers in Microbiology 2025 — sleep disruption and Faecalibacterium depletion — Link
Gut Microbiota for Health 2025 — imidazole propionate / Nature cardiovascular biomarker — Link
Stanford / Cell (fermented foods study) — Link
Disclaimer: The Wellness Brew is for informational purposes only and does not constitute medical advice. The content published here is not intended to diagnose, treat, cure, or prevent any disease or health condition. Always consult a qualified healthcare professional before making any changes to your diet, supplement routine, or lifestyle.