The Wellness Brew - Issue 09

Cortisol is one of the most important hormones in the body — and one of the least understood. It is not simply a stress hormone. It governs energy, immune function, sleep timing, metabolism, and cognitive performance. When it is chronically elevated, every one of those systems pays a price. This week, we break down the physiology, the downstream consequences, and what the evidence actually says you can do about it. But first, we filtered the noise — here's what's worth knowing this week.

The Clothes on Your Baby May Contain More Harmful Chemicals Than You Think — And Cotton Is Not the Safe Alternative You Assume

Infant clothing consistently has some of the highest chemical concentrations of any textile category. A 2019 peer-reviewed study published in Environment International tested socks sold for infants and children aged 0–4 years and found BPA in 90.6% of samples. A 2025 study published in Environmental Research analyzed infant textiles more broadly and found a range of harmful chemicals including phthalates, genotoxic compounds, and endocrine disruptors across multiple garment types. 

The counterintuitive finding worth knowing: cotton is not the safe alternative. Studies consistently show that cotton adsorbs phthalates and BPA from the environment during manufacturing more readily than many synthetic fabrics — with one study finding BPA levels 25-fold higher in higher-cotton-content socks compared to lower-cotton alternatives. The chemicals bind to fibers during dyeing, finishing, and pesticide application throughout the production process, and traditional laundering does not remove them completely.

The practical solution is not to avoid cotton entirely — it is to choose certified organic cotton. GOTS (Global Organic Textile Standard) and OEKO-TEX Standard 100 are the two certifications worth looking for. Both verify that textiles have been produced without harmful pesticides and finished without the chemical treatments responsible for most contamination. For baby clothing specifically — where skin contact is constant and exposure duration is highest — this distinction matters more than in any other clothing category. Freire C, et al. Environment International, 2019 | Domínguez-Liste A, et al. Environmental Research, 2025 

Nattokinase Is Trending as a Heart Health Supplement. Here Is What the Evidence Actually Shows.

Nattokinase — an enzyme derived from natto, a traditional Japanese fermented soybean dish — is circulating on social media with claims it dissolves arterial plaque and reduces LDL cholesterol. The underlying science is more nuanced than most posts suggest.

Nattokinase is a fibrinolytic enzyme that breaks down fibrin, the structural protein in blood clots. The proposed mechanism is biologically plausible, and some early results are promising: a 2022 clinical study of 1,062 participants found that high-dose nattokinase was associated with a 36% reduction in arterial plaque size over 12 months. A 2023 meta-analysis of six randomized controlled trials found significant blood pressure reductions.

Three things the social media posts are not mentioning. First, the plaque reduction was at the highest dose tested — at lower doses, separate studies found no effect, and the 2023 meta-analysis found low-dose nattokinase actually worsened LDL levels. Second, most trials are small and have not been independently replicated at scale. Third — most importantly — nattokinase is a blood-thinning agent. Combining it with aspirin, warfarin, or other blood thinners carries real bleeding risk.

The honest summary: promising early research, not yet at the evidence level of omega-3s or berberine for cardiovascular health. Worth watching — not yet worth acting on. Chen et al., Frontiers in Cardiovascular Medicine, 2022 | Li et al., Reviews in Cardiovascular Medicine, 2023

Stress and Cortisol: What Chronic Stress Is Actually Doing to Your Body

Stress is often treated as a necessary evil — something that comes with the job, the season, or the stage of life. And to a point, that framing is correct. Some stress is not only normal, it is biologically useful. The problem is not stress itself. It’s when that stress doesn’t turn off. When that happens, the same system designed to protect you begins working against you.

What cortisol is and how it works

Cortisol is a hormone produced by the adrenal glands — two small glands that sit on top of the kidneys — in response to a perceived threat. Think of it as the body's internal alarm system. Useful when the alarm is warranted. Damaging when it never stops ringing.

The system that controls cortisol release is called the HPA axis — hypothalamic-pituitary-adrenal. In plain terms: the brain detects a stressor, the hypothalamus sends a signal to the pituitary gland, which sends a signal to the adrenal glands, which release cortisol. Three steps, all happening within seconds.

In the short term, this response is a masterpiece of biological design. Cortisol raises blood sugar to fuel muscles and the brain, sharpens focus and alertness, temporarily suppresses digestion, reproduction, and immune activity to redirect energy toward the immediate demand, and accelerates heart rate and blood pressure to prepare the body to act. This is the system working exactly as it was designed to.

Cortisol also follows a healthy daily rhythm. Levels peak naturally 30–45 minutes after waking — a phenomenon called the cortisol awakening response — providing the energy and alertness that gets you out of bed and into the morning. This daily peak is a sign of a healthy, well-regulated system, not a problem to be solved.

What goes wrong is chronic activation. When stress is sustained for weeks, months, or years without meaningful recovery, the HPA axis remains switched on, and the body's suppressed systems begin to break down. Digestion, immunity, sleep, hormonal balance, and cognitive function all suffer under prolonged cortisol elevation.

There is also a compounding mechanism called glucocorticoid receptor resistance. When cells are flooded with cortisol day after day, they begin to tune it out — the way a person stops noticing background noise after long enough. Cortisol receptors become desensitized, and the body compensates by producing even more cortisol to achieve the same effect. The alarm grows louder to get the same response, creating a cycle that becomes harder and harder to interrupt. [1]

What chronic cortisol elevation is doing downstream

Sleep

Cortisol has an inverse relationship with melatonin, the hormone that initiates sleep. When cortisol is elevated in the evening, melatonin production is suppressed and sleep onset is delayed. Chronic evening stress directly degrades the quality and timing of sleep.

This begins a feedback loop that is well-documented and difficult to stop: poor sleep raises cortisol levels the following day, which further impairs the next night's sleep, which raises cortisol further. Each turn of the cycle compounds the last. [2]

Immune function

In the short term, cortisol is anti-inflammatory — it is precisely why doctors prescribe corticosteroids for acute inflammation. But chronically elevated cortisol eventually produces the opposite effect.

As cells develop glucocorticoid receptor resistance, the immune system loses its primary regulatory brake. Rather than staying suppressed, it becomes dysregulated — shifting paradoxically toward a chronic low-grade inflammatory state. A 2025 review published in the International Journal of Molecular Sciences found that chronic stress leads to impaired HPA axis feedback, glucocorticoid receptor resistance, and a pro-inflammatory environment linked to autoimmune disease, metabolic dysfunction, and accelerated biological aging. [3] 

In the simplest terms — chronic stress drives chronic inflammation.

Visceral fat

Cortisol promotes fat storage — but not evenly. Abdominal fat cells carry significantly more cortisol receptors than fat cells elsewhere in the body, making the belly disproportionately responsive to sustained cortisol elevation. Cortisol raises blood glucose to prepare the body for action, which triggers insulin release, which drives fat storage — concentrated in the visceral compartment.

Visceral fat is not a cosmetic concern and you may not even appear to have belly fat. Instead, visceral fat surrounds the organs — the liver, kidneys, and intestines — and releases its own inflammatory compounds independently of what is circulating in the bloodstream. Visceral fat accumulation is independently associated with cardiovascular disease, type 2 diabetes, metabolic syndrome, and all-cause mortality at a level that subcutaneous fat — the fat just beneath the skin — does not replicate. [4] 

Muscle breakdown

Cortisol is a catabolic hormone — meaning it breaks down tissue to release amino acids for glucose production during perceived stress. Chronically elevated cortisol degrades lean muscle mass over time, reducing resting metabolic rate and creating a hormonal environment that simultaneously stores fat and burns muscle. 

Cognition and memory

The hippocampus — the brain region primarily responsible for memory formation and learning — is particularly dense with cortisol receptors, making it particularly vulnerable to sustained cortisol exposure. Chronic elevation is associated with hippocampal volume reduction, impaired memory consolidation, and deficits in cognitive flexibility and executive function.

A 2023 review published in Cells found that chronic stress and cortisol dysregulation are closely linked to the progression of neurodegenerative conditions, including Alzheimer's and Parkinson's disease, through cortisol-driven neuroinflammation in the central nervous system. This data is observational and the direction of causality in humans is not fully established — but the biological mechanism is specific and the associations are consistent and large enough to warrant attention. [1]

The interventions with the best evidence

Now that we have covered what chronic stress is doing to the body, here is what the evidence says you can do about it. 

Sleep

Sleep is the most powerful cortisol regulator available. The bidirectional relationship between sleep and cortisol means that improving sleep directly and measurably reduces HPA axis activation the following day. Consistent bed and wake times support the healthy cortisol awakening response and reinforce the diurnal rhythm that keeps cortisol appropriately timed. The practical steps for improving sleep architecture were covered in depth in Issue 03 and apply directly here.

Mindfulness and structured breathing

Mindfulness-Based Stress Reduction — an 8-week structured program developed at the University of Massachusetts — is the most extensively studied behavioral intervention for cortisol reduction. A 2025 randomized controlled trial in healthcare workers found that an 8-week MBSR program significantly reduced cortisol levels in the short term, with sustained benefits at follow-up. A large multi-site randomized controlled trial (RCT) published in Nature Human Behaviour in 2024 found that self-administered mindfulness interventions significantly reduced perceived stress across multiple populations without requiring in-person instruction. [5]

Mindfulness practice reduces amygdala reactivity — the brain region that initiates the HPA axis stress response — and strengthens prefrontal cortex regulation of that response. The alarm becomes easier to turn off. 

10 minutes of breath-focused sitting meditation daily — returning attention to the physical sensation of breathing each time the mind wanders — is the entry-level dose that appears consistently across the RCT literature. For immediate, acute stress reduction, the physiological sigh is the most evidence-supported real-time technique: a double inhale through the nose followed by a long slow exhale through the mouth. One to three repetitions activate the parasympathetic nervous system within seconds and can be used anywhere, at any time. 

Exercise — with an important nuance

Moderate-intensity aerobic exercise is consistently associated with reduced cortisol and improved HPA axis regulation over time. Regular movement is one of the most well-supported interventions for stress physiology across the research literature.

The nuance worth knowing: excessive high-intensity training — particularly when already chronically stressed and sleep-deprived — can raise cortisol further rather than reduce it. The body does not distinguish between physical and psychological stress. When physiological reserves are already depleted, adding intense training load can become an additive stressor rather than a release valve. [6]

Time in nature

This one may surprise people. Time spent in natural environments is associated with measurable reductions in cortisol, blood pressure, and heart rate across multiple studies. A 2019 study found that spending at least 120 minutes per week in nature was associated with significantly better health and wellbeing outcomes — and that the benefit could be accumulated across multiple shorter sessions rather than requiring a single long exposure. How it works is not fully understood but likely involves reduced sensory load, lower ambient noise, and attentional restoration — the brain's capacity to recover from directed focus. [7]

Ashwagandha — the evidence and the caveats

Ashwagandha (Withania somnifera) is an adaptogen — a class of herbs used in Ayurvedic medicine for centuries to help the body regulate its stress response. The clinical evidence has strengthened considerably in recent years. A 2025 systematic review and meta-analysis of 15 randomized controlled trials covering 873 participants, published in BJPsych Open, found that ashwagandha supplementation significantly reduced anxiety compared to placebo. A separate 2025 meta-analysis found significant reductions in measured cortisol levels across RCTs. Individual trials have used doses ranging from 240mg to 600mg of standardized root extract, with KSM-66 being the most studied and consistently performing form. [8]

The caveats are worth stating clearly. Rare cases of liver toxicity have been reported with high doses. Ashwagandha is not recommended during pregnancy or for people on thyroid medication, as it may affect thyroid hormone levels. Daily use long-term may chronically suppress cortisol, which as we touched on earlier is a critical part of the body’s natural processes. 

The honest framing of the evidence: ashwagandha is a well-supported tool for acutely stressful periods — a particularly demanding work stretch, a season of disrupted sleep, a period of elevated psychological load. But it is better approached as a situational supplement than as a permanent daily addition.

What this means in practice

Chronic stress is not a mindset problem — it is a physiological state with a specific hormonal mechanism and measurable downstream consequences on nearly every system in the body. The interventions above are not soft lifestyle advice. They are documented levers for reducing cortisol and interrupting the downstream cascade. The Actionable Takeaways below are prioritized by evidence, strength, and accessibility.

Four things you can do this week:

1. Set a non-negotiable wind-down boundary into your evening. The cortisol-melatonin relationship makes evening stress the single highest-leverage target for intervention. Cortisol is supposed to be at its lowest point in the hours before sleep — and any activity that sustains mental activation in that window directly delays and degrades sleep onset. Set a specific time — not a range, a time — after which work communications stop, screens dim, and the nervous system is given a signal that the day is over. This does not require an elaborate routine. It requires consistency. The boundary itself is the intervention.

2. Add 10–20 minutes of mindfulness or structured breathing daily. This is the intervention with the strongest and most replicated evidence for measurable cortisol reduction in the behavioral literature. 

Start simple —  10 minutes of breath-focused sitting meditation daily is the entry-level dose that appears consistently across the clinical trial literature. Sit comfortably, eyes closed, and return attention to the physical sensation of breathing each time the mind wanders. 

For immediate, real-time stress reduction, the physiological sigh is the most evidence-supported acute technique: a double inhale through the nose — two sharp inhales, the second drawing in a little more air — followed by a long, slow exhale through the mouth. One to three repetitions activate the parasympathetic nervous system within seconds.

3. Protect your moderate exercise — and resist the urge to use hard training as a stress outlet when already depleted. Regular moderate-intensity movement is one of the most well-supported interventions for cortisol regulation. When already chronically stressed and under-slept, high-intensity training can raise cortisol rather than reduce it. Focus on Zone 2 cardio or a moderate strength session.

4. Spend two hours in nature per week. This does not require a wilderness retreat. Walking in a park, sitting outside during lunch, hiking on a weekend — the two-hour threshold can be accumulated across the week in sessions of any length. The cortisol-reducing effect of natural environments is dose-responsive and does not require extended immersion to be meaningful.

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Wellness, filtered.

The Wellness Brew

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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.