October 16th, 2025 | Issue #174

Winter Might Be the Best Time to Start Cold Plunging

Cold plunges are an easy summer sell, its hot, you’re sweaty — but winter? Hear me out: because your skin is cold and the air is colder, water that's 40–50°F often feels kinder. This week, we show you how to use winter to your advantage, what the evidence says, how to do it safely, and the best tubs to buy.

TWO BIG THINGS THIS WEEK🦷 Japan flags a tooth‑regeneration drug (TRG035) as an Orphan—human trial plan postedWhy it matters: Blocking USAG‑1 to regrow natural teeth just took a regulatory step: Japan’s MHLW just granted orphan designation (Japan’s process of copyrighting things) for treating severe congenital oligodontia. A participating hospital has also published the clinical trial plan page—another sign this is moving from sci‑fi to clinic. This might be worth travelling to Japan for if approved! Toregem

💪 Muscle‑sparing weight‑loss: semaglutide + myostatin antibody hits 26‑week markWhy it matters: At EASD, 26‑week Phase 2 COURAGE data showed adding trevogrumab (anti‑myostatin) to semaglutide prevented ~½ of lean‑mass loss while shifting more of the weight change to fat (≈82–93% of total loss in combo arms). That’s a big deal for healthy aging, where strength and function matter. I’ve heard about this before and I think its a great idea. Regeneron Investor Relations

Winter’s Cheat Code: Does Cold Water Feel Warm?

TL;DR: Winter can be the easiest time to start cold plunging. Keep it short (~3 min), keep it safe, don’t put it right after your gym or training session, and pick gear that fits your space and budget. Keep an eye out for my personal tub remake in a future video.

Flip the Script: When the Temps Are Low

I’ll be honest — every time I stare down a cold tub, my first instinct is to bail. Then I do the thing, count my breaths, and the switch flips: mood up, mind sharp, energy on a high for hours. In my experience, Winter made this easier, not harder — the water often feels less shocking when the air is colder. Below, we separate hype from helpful.We underestimate how relatively cold it feels. In summer, 50°F water is a slap; in winter, that same water can feel surprisingly tolerable.

Why Try a Winter Plunge at All?

We underestimate how relatively cold it feels. In Summer, 50°F water is a slap; in Winter, that same water can feel surprisingly tolerable. When I lived in Austin, Texas, the city's favorite Summertime hangout, Barton Springs, sits ~68–70°F year‑round — “cool” in July, almost “warm” in January — a perfect illustration of context effects. Austin Texas

Receipts, Not Reels: What does the human data actually show?

Recovery & soreness: Systematic reviews suggest that cold-water immersion (less than 59°F) can modestly reduce delayed-onset muscle soreness compared to passive rest, but study quality is mixed. Cochrane

Strength gains caveat: Repeated post‑lifting CWI can blunt hypertrophy signaling and fiber growth over time (strength not always affected). If gains are the goal, skip ice baths right after resistance sessions. NIH Brage

Metabolism: Mild cold exposure recruits brown adipose tissue and increases energy expenditure in adults — part of why you feel “revved.” New England Journal of Medicine

Neurochemistry & mood: Human immersions elevate norepinephrine quickly (alertness, focus); case reports and small series suggest mood benefits, but larger trials are still needed. University of Arizona (Yeah Tucson!)

Immune signaling: In controlled endotoxemia, a training program combining breathing + cold exposure attenuated pro‑inflammatory cytokines and increased IL‑10 — promising but not a direct endorsement of cold plunges as “immune therapy.” PNAS

Shiver Smart, Not Hard: How do you get the upside—safely and in ~3 minutes?

Who should be cautious: People with cardiovascular disease, uncontrolled hypertension, arrhythmias, Raynaud’s, neuropathy, or pregnancy should talk to a clinician first. Sudden immersion below ~60°F can provoke dangerous cold shock (gasp, tachycardia). www.heart.org

Start simple: Begin with 30–60 seconds at ~55–60°F, breathing light and slow through the initial reflex. Build toward ~3 minutes — many users find most benefit in that window.

Timing: For muscle and strength goals, separate heavy lifting and cold by ≥6–8 hours (or save CWI for endurance/recovery days). NIH Brage

Warm‑up smart: Rewarm passively (robe, breath work, movement, sunlight) before heat. Contrast therapy is great — just avoid scalding showers immediately after if dizziness is a risk.

Next Up (+ What to Buy): Where is Science Going—and Which Tubs are Worth Your Money?

The science is evolving, but the practical upside is clear: better mood and alertness, potentially faster recovery, and a habit that builds stress resilience. We’re refreshing our Best Cold Plunge guide in 2026, even though not much has changed; until then, last year’s winners still hold up for most budgets and setups. Best Cold Plunge for Longevity — our buyer’s guide.

MARKET INTEL (past 60 days)

FDA OKs subcutaneous Keytruda (QLEX). Faster 1–2‑minute injections across most IV pembrolizumab solid‑tumor indications; clinic efficiency win ahead of 2028 LOE. So what: expect formulary jockeying and new site‑of‑care dynamics. U.S. Food and Drug Administration

C2N files for FDA review of an Alzheimer’s blood test. Part of the shift to minimally invasive AD diagnostics. So what: if cleared, triage to PET/CSF could improve access and costs. C2N Diagnostics

Alnylam’s ZENITH CVOT (zilebesiran) begins dosing. ~11,000 patients, 35 countries to test biannual siRNA for hypertension outcomes. So what: first hard‑outcomes data for renin‑angiotensin siRNA in high‑risk patients. Alnylam Investor Relations

AstraZeneca breaks ground on a $4.5B Virginia facility. Scope expanded; part of a $50B U.S. build‑out by 2030. So what: more U.S. API and biologics capacity, plus obesity and oncology lines; jobs and policy optics. Reuters

Klotho–Turn Bio LOI expires. Parties walked; Klotho cites strategy fit. So what: reprogramming assets remain in play; watch for follow‑on bids. PR Newswire

Stay Cold!

Brent

Check our latest Podcast Episode!

I dig into wealth × longevity—what “longevity risk” means for real people and how to plan for a longer life financially.Listen to it here > YouTube, Apple Podcasts, and Spotify.

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YOUR Weekly LONGEVITY PLAN — Cold Edition

✅ Step 1: Track it (measurable): Log 3 x 3‑minute cold finishes in your showers this week (remember you have ‘hey Siri/Google to start timers). Record mood/alertness 30 minutes later (1–10 scale).

✅ Step 2: Make it accessible: Try one coached session at a local studio to learn breathing and exits safely. Find options via our Cold Plunge marketplace (typical session $20–$40). Spannr

✅ Step 3: Forward‑looking: Sometimes this sounds like a broken record, and seriously, make sure to ask your clinician, “Any reasons I should avoid CWI (especially if you have a cardiac history, on BP meds, Raynaud’s) — and they might have a safe temp/duration they could recommend when you do. I know I started cold plunging at the very cold end of the spectrum (35-38 degrees) and actually started doing slightly ‘warmer’ plunges (when I have the option)

Sources for this newsletter this week: Research compiled from 30+ longevity publications, biotech funding reports, clinical trial databases, and Google News.Medical disclaimer: Content is for educational purposes only and is not medical advice. Always consult a qualified healthcare professional before making changes to your health regimen.Affiliate disclosure: Spannr may receive compensation when you click partner links and make a purchase. As an Amazon Associate, we earn from qualifying purchases. Some products may be provided at no cost for evaluation; opinions are our own.HIPAA/PHI notice: Do not send personal medical information to this inbox. Spannr does not collect or store PHI via email.

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