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[159.112.244.25]) by mx.google.com with UTF8SMTPS id 6a1803df08f44-8a5973e74e9si110320216d6.197.2026.04.03.14.45.55 for (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 03 Apr 2026 14:45:55 -0700 (PDT) Received-SPF: pass (google.com: domain of bounce+30b528.39b08c6-tjphuhs=gmail.com@mg-d1.substack.com designates 159.112.244.25 as permitted sender) client-ip=159.112.244.25; Authentication-Results: mx.google.com; dkim=pass header.i=@mg-d1.substack.com header.s=k1 header.b=eapw8HfT; dkim=pass header.i=@mailgun.org header.s=mg header.b="Rx+Kau5/"; spf=pass (google.com: domain of bounce+30b528.39b08c6-tjphuhs=gmail.com@mg-d1.substack.com designates 159.112.244.25 as permitted sender) smtp.mailfrom="bounce+30b528.39b08c6-tjphuhs=gmail.com@mg-d1.substack.com"; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=substack.com DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg-d1.substack.com; q=dns/txt; s=k1; t=1775252755; x=1775259955; h=List-Unsubscribe-Post: List-Unsubscribe: List-Post: List-Id: List-Archive: List-Owner: Reply-To: In-Reply-To: References: Sender: Sender: Date: Message-Id: To: To: From: From: Subject: Subject: Content-Type: Mime-Version: X-Feedback-Id; bh=vSdH4q348WiKrz1DAl7IYcBH5tY2aiQKae1+OFXaNRE=; b=eapw8HfTZeHZjt4yHLxuy4It9C2tjI5dwG5sMdcD9TXQpK+NWV9cgvFxMFMOA5Y920W/Fv9nQW0ygdK7lgYdbmMw9x/oTisAnnAesvG30Ij0Jo/RHeMLN/Bpbus13TFNQ0bJx7ZU4jXTvFDtvhaALfor29jwIkCS3xYUks8AgXE= DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mailgun.org; q=dns/txt; s=mg; t=1775252755; x=1775259955; h=List-Unsubscribe-Post: List-Unsubscribe: List-Post: List-Id: List-Archive: List-Owner: Reply-To: In-Reply-To: References: Sender: Sender: Date: Message-Id: To: To: From: From: Subject: Subject: Content-Type: Mime-Version: X-Feedback-Id; bh=vSdH4q348WiKrz1DAl7IYcBH5tY2aiQKae1+OFXaNRE=; b=Rx+Kau5/nl5qmaIs8FUQYZYazFPgoSmpmg5LHPDSTxEHo1Hpn0ZN9ZdaJPrhz5oGHnWusDyxT1o9VNBpqSSMupcYyICHXlxhRVEdo94Pdq3x1ZVsGnhqPUMSt2xeO2CvHeR1LTS1p/oDil0ie4ozHf8TD2gH8VEWnViI9YWUzuA= X-Mailgun-Sid: WyIxMWU0ZSIsInRqcGh1aHNAZ21haWwuY29tIiwiMzliMDhjNiJd X-Feedback-Id: postmaster@mg-d1.substack.com:post:614a1297c57bbbe25fa40e08:mailgun Received: by 49e938f1db870393a4d65e77c1fb0e952011b277cfe67ff34425515852b76b42 with HTTP id 69d0351329f95355fce321a7; Fri, 03 Apr 2026 21:45:55 GMT X-Mailgun-Sending-Ip: 159.112.244.25 X-Mailgun-Batch-Id: 69d035133cfe59f61d852ff9 Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="dd0fbc1e53e0f776d8728ebb179b3a747a54d96db7fa5dd340639d55832a" Subject: Sauna people, you want to know about this From: Bryan Johnson from Bryan Johnson To: tjphuhs@gmail.com X-Mailgun-Tag: post X-Mailgun-Track-Clicks: false Message-Id: <20260403214547.3.372a7168e04cd681@mg-d1.substack.com> Date: Fri, 3 Apr 2026 21:45:47 +0000 Feedback-Id: post-193114951:cat-post:pub-5008442:substack Sender: Bryan Johnson from Bryan Johnson References: In-Reply-To: Reply-To: Bryan Johnson from Bryan Johnson List-Owner: List-Url: List-Archive: List-Id: List-Post: List-Unsubscribe: List-Unsubscribe-Post: List-Unsubscribe=One-Click X-Mailgun-Variables: {"category": "post", "email_generated_at": "1775252754778", "is_freemail": "true", "post_audience": "everyone", "post_id": "193114951", "post_type": "newsletter", "pub_community_enabled": "true", "publication_id": "5008442", "subdomain": "bryanjohns0n", "user_id": "273622398"} --dd0fbc1e53e0f776d8728ebb179b3a747a54d96db7fa5dd340639d55832a Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable View this post on the web at https://bryanjohns0n.substack.com/p/sauna-peop= le-you-want-to-know-about I baked in a 195=C2=B0F (90=C2=B0C) dry sauna for 38 minutes. It was painful. It was also the minimum necessary to saunamaxx.=20 Many think that sweating is the goal. The goal is to get your core body te= mperature to 102.2=C2=B0F (39=C2=B0C). Below that threshold you=E2=80=99re = getting maybe half the health benefits sauna offers. The thing that most surprised me from this experiment is experiencing what = 102.2 =C2=B0F (39=C2=B0 C) actually feels like. The level of discomfort.=20 The big sauna benefits happen when your core body temp reaches 102.2 =C2=B0= F (39=C2=B0 C). At this temp, the body releases heat shock proteins (HSPs).= They act inside your cells as molecular chaperones, catching misfolded pro= teins and refolding them before they clump together. Protecting metabolism,= brain function, and cellular longevity. I wanted to verify that my sauna protocol was getting my core body temp to = 102.2 =C2=B0F (39=C2=B0 C), and even up to 103=C2=B0F (39.4=C2=B0 C). To do= that, I had two options, a rectal probe or swallow a jelly bean sized pill= =2E I opted for the pill. The pill then= goes through my digestive track, read= ing out my core body temperature every 30 seconds until it exits on the oth= er side.=20 Up until now, I was relying upon an ear probe which has a ~1=C2=B0F (0.5= =C2=B0C) error margin. What shown in the image below:=20 1. My core body temperature hit a peak of 102.65=C2=B0F (39.25=C2=B0C), the= heat shock protein activation threshold.=20 2. The dry sauna temp was 195=C2=B0F (90.5=C2=B0C).=20 3. I was in the sauna for about 38 minutes.=20 4. My subjective experience: I was dying.=20 5. My waking baseline core body temp hit a trough of 96.08=C2=B0F (35.6=C2= =B0C) before activity. 6. Pre-sauna exercise elevated core temperature by 2.52=C2=B0F (1.4=C2=B0C)= , aided by natural circadian rhythm following wake-up. 7. Sauna increased my core temperature by an additional 3.6=C2=B0F (2=C2=B0= C) 8. I sat at 195=C2=B0F and my core temp didn=E2=80=99t budge for 16 minutes= =2E=20 9. After leaving the sauna, I cooled down 15.8% faster than I heated up. 10= =2E Both the long lag and faster coo= ling indicate heat acclamation (I=E2=80= =99ve done over 200 sauna sessions in the past year). The reading form the temperature gauge inside the sauna, at my eye level.= =20 CAVEAT Does this mean you need to sit in a dry sauna at 195=C2=B0F (90.5=C2=B0C) f= or 38 minutes? Not necessarily. In this session I was cooling my face and neck to test whether active cooli= ng could prevent thermal skin damage. That cooling worked against my core t= emperature rise, extending the time needed to hit the HSP threshold. The 40= minutes reflects that tradeoff. We will next experiment by removing the cooling to evaluate the time to hit= the heat shock threshold of 102.65=C2=B0F (39.25=C2=B0C).=20 Here is some of what we know about sauna, core temperature, and heat shock = protein activation. Dry sauna is unique in engaging cardiovascular, skin, and molecular respons= es to thermal challenges. While the cardiovascular, skin and detox (sweating) benefits are already ob= tainable at smaller core temperature increases, starting with 0.36-0.9=C2= =B0F (0.2-0.5=C2=B0C) shifts, the molecular heat responses including Heat S= hock Protein expression and activation require more pronounced core tempera= tures increases. While this mechanism makes dry sauna safe and tolerable, it also means one = must be highly intentional to achieve the deeper biological impacts associa= ted with heat shock protein activation, including neuroprotection, long-ter= m metabolic improvements and cellular longevity. Evidence suggests a minimum threshold of approximately 102.2=C2=B0F (39=C2= =B0C) is required for robust HSP induction, though this varies by cell and = tissue type. In vitro studies on human white blood cells indicate that 101.3=C2=B0F (38.= 5=C2=B0C) is insufficient for HSP induction (104=C2=B0F (40=C2=B0C) was suf= ficient in the same study), whereas 102.2=C2=B0F (39=C2=B0C) significantly = increases HSP70 (a key inducible protein) in monocytes. Clinical observations in healthy young men showed that a core temperature r= ise above 101.3=C2=B0F (38.5=C2=B0C) (reaching over 101.48=C2=B0F (38.6=C2= =B0C)) during an initial sauna session induced HSP72. However, heat acclima= tion by the 10th session limited the core temperature to 100.76=C2=B0F (38.= 2=C2=B0C), largely eroding the HSP response. Hot water immersion protocol targeting a rectal temperature of 103.1=C2=B0F= (39.5=C2=B0C) for 60 minutes produced significant increases in both HSP27 = and HSP70. Heated exercise protocols reaching 103.1=C2=B0F (39.5=C2=B0C) resulted in m= eaningful increases in HSP90, the initiator of the heat shock protein expre= ssion cascade Unsubscribe https://substack.com/redirect/2/eyJlIjoiaHR0cHM6Ly9icnlhbmpvaG5= zMG4uc3Vic3RhY2suY29tL2FjdGlvbi9kaXNhYmxlX2VtYWlsP3Rva2VuPWV5SjFjMlZ5WDJsa0= lqb3lOek0yTWpJek9UZ3NJbkJ2YzNSZmFXUWlPakU1TXpFeE5EazFNU3dpYVdGMElqb3hOemMxT= WpVeU56VTBMQ0psZUhBaU9qRTRNRFkzT0RnM05UUXNJbWx6Y3lJNkluQjFZaTAxTURBNE5EUXlJ= aXdpYzNWaUlqb2laR2x6WVdKc1pWOWxiV0ZwYkNKOS53Y2pyRHB6dUJwNkpISTRmSFcyLWFPRFg= 4MHJ2Skw3LV9UUGZZLWFYQ0lZIiwicCI6MTkzMTE0OTUxLCJzIjo1MDA4NDQyLCJmIjp0cnVlLC= J1IjoyNzM2MjIzOTgsImlhdCI6MTc3NTI1Mjc1NCwiZXhwIjoyMDkwODI4NzU0LCJpc3MiOiJwd= WItMCIsInN1YiI6ImxpbmstcmVkaXJlY3QifQ.U2X0Tbkb1mnKtiP064WWWhLGBM3hR03Mgf_ho= uDPy6E? --dd0fbc1e53e0f776d8728ebb179b3a747a54d96db7fa5dd340639d55832a Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable = Sauna people, you want to know about this 3D""
I baked in a 195°F (90°C) dry sauna for 38 minutes.
=
T= 7;     ­͏     ­͏     &= #173;͏     ­͏     ­͏   =   ­͏     ­͏     ­͏= ;     ­͏     ­͏     &#= 173;͏     ­͏     ­͏   &= #8199; ­͏     ­͏     ­͏=     ­͏     ­͏     = 73;͏     ­͏     ­͏   &#= 8199; ­͏     ­͏     ­͏ =     ­͏     ­͏     = 3;͏     ­͏     ­͏   = 199; ­͏     ­͏     ­͏ &= nbsp;   ­͏     ­͏     ­= ;͏     ­͏     ­͏   Q= 99; ­͏     ­͏     ­͏ &n= bsp;   ­͏     ­͏     ­= ͏     ­͏     ­͏   ̳= 9; ­͏     ­͏     ­͏ &nb= sp;   ­͏     ­͏     ­&= #847;     ­͏     ­͏    = ; ­͏     ­͏     ­͏ &nbs= p;   ­͏     ­͏     ­&#= 847;     ­͏     ­͏    = ­͏     ­͏     ­͏  = ;   ­͏     ­͏     ­= 47;     ­͏     ­͏     = ­͏     ­͏     ­͏  =   ­͏     ­͏     ­T= 7;     ­͏     ­͏     &= #173;͏     ­͏     ­͏   =   ­͏     ­͏     ­͏= ;     ­͏     ­͏     &#= 173;͏     ­͏     ­͏   &= #8199; ­͏     ­͏     ­͏=     ­͏     ­͏     = 73;͏     ­͏     ­͏   &#= 8199; ­͏     ­͏     ­͏ =     ­͏     ­͏     = 3;͏     ­͏     ­͏   = 199; ­͏     ­͏     ­͏ &= nbsp;   ­͏     ­͏     ­= ;͏     ­͏     ­͏   Q= 99; ­͏     ­͏     ­͏ &n= bsp;   ­͏     ­͏     ­= ͏     ­͏     ­͏   ̳= 9; ­͏     ­͏     ­͏ &nb= sp;   ­͏     ­͏     ­&= #847;     ­͏     ­͏    = ; ­͏     ­͏     ­͏ &nbs= p;   ­͏     ­͏     ­&#= 847;     ­͏     ­͏    = ­͏     ­͏     ­͏  = ;   ­͏     ­͏     ­= 47;     ­͏     ­͏     = ­͏     ­͏     ­͏  =   ­͏     ­͏     ­T= 7;     ­͏     ­͏     &= #173;͏     ­͏     ­͏   =   ­͏     ­͏     ­͏= ;     ­͏     ­͏     &#= 173;͏     ­͏     ­͏   &= #8199; ­͏     ­͏     ­͏=     ­͏     ­͏     = 73;͏     ­͏     ­͏   &#= 8199; ­͏     ­͏     ­͏ =     ­͏     ­͏     = 3;͏     ­͏     ­͏   = 199; ­͏     ­͏     ­͏ &= nbsp;   ­͏     ­͏     ­= ;͏     ­͏     ­͏   Q= 99; ­͏     ­͏     ­͏ &n= bsp;   ­͏     ­͏     ­= ͏     ­͏     ­͏   ̳= 9; ­͏     ­͏     ­͏ &nb= sp;   ­͏     ­
Forwarded this email? Subscribe here for more

Sauna people, you want to know abou= t this

I baked in a 195°F (90= °C) dry sauna for 38 minutes.

It was painful.

It was also the minimum necessary to saunamaxx.
=
Many think that sweating is the goal. The goal is to get your co= re body temperature to 102.2°F (39°C). Below that threshold you&#= 8217;re getting maybe half the health benefits sauna offers.

= The thing that most surprised me from this experiment is experiencing= what 102.2 °F (39° C) actually feels like. The level of discomfo= rt.

The big sauna bene= fits happen when your core body temp reaches 102.2 °F (39° C). At= this temp, the body releases heat shock proteins (HSPs). They act inside y= our cells as molecular chaperones, catching misfolded proteins and refoldin= g them before they clump together. Protecting metabolism, brain function, a= nd cellular longevity.

I wanted to verify that my sauna= protocol was getting my core body temp to 102.2 °F (39° C), and = even up to 103°F (39.4° C). To do that, I had two options, a rect= al probe or swallow a jelly bean sized pill. I opted for the pill. The pill= then goes through my digestive track, reading out my core body temperature= every 30 seconds until it exits on the other side.

U= p until now, I was relying upon an ear probe which has a ~1°F (0.5= 6;C) error margin.

What s= hown in the image below:
1. My core body temperature hit a= peak of 102.65°F (39.25°C), the heat shock protein activation th= reshold.
2. The dry sauna temp was 195°F (90.5°C= ).
3. I was in the sauna for about 38 minutes.
= 4. My subjective experience: I was dying.
5. My waki= ng baseline core body temp hit a trough of 96.08°F (35.6°C) befor= e activity.
6. Pre-sauna exercise elevated core temperature= by 2.52°F (1.4°C), aided by natural circadian rhythm following w= ake-up.
7. Sauna increased my core temperature by an additi= onal 3.6°F (2°C)
8. I sat at 195°F and my co= re temp didn’t budge for 16 minutes.
9. After leavin= g the sauna, I cooled down 15.8% faster than I heated up. 10. Both the long= lag and faster cooling indicate heat acclamation (I’ve done over 200= sauna sessions in the past year).

<= /table>
Bryan Johnson
 
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READ IN APP3D""
 
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The reading form the temperature gauge inside the sauna, at my eye lev= el.

3D""


CAVEAT

Does this mean you n= eed to sit in a dry sauna at 195°F (90.5°C) for 38 minutes? Not n= ecessarily.

In this session I was cooling my face an= d neck to test whether active cooling could prevent thermal skin damage. Th= at cooling worked against my core temperature rise, extending the time need= ed to hit the HSP threshold. The 40 minutes reflects that tradeoff.

We will next experiment by removing the cooling to evaluate the ti= me to hit the heat shock threshold of 102.65°F (39.25°C).

3D""

Here i= s some of what we know about sauna, core temperature, and heat shock protei= n activation.

Dry sauna is unique in engaging cardiovas= cular, skin, and molecular responses to thermal challenges.

While the cardiovascular, skin and detox (sweating) benefits are al= ready obtainable at smaller core temperature increases, starting with 0.36-= 0.9°F (0.2-0.5°C) shifts, the molecular heat responses including = Heat Shock Protein expression and activation require more pronounced core t= emperatures increases.

While this mechanism makes dry sauna= safe and tolerable, it also means one must be highly intentional to achiev= e the deeper biological impacts associated with heat shock protein activati= on, including neuroprotection, long-term metabolic improvements and cellula= r longevity.

Evidence suggests a minimum threshold of= approximately 102.2°F (39°C) is required for robust HSP inductio= n, though this varies by cell and tissue type.

In vitro studies on human white blood cells indicate that 101.3= 76;F (38.5°C) is insufficient for HSP induction (104°F (40°C= ) was sufficient in the same study), whereas 102.2°F (39°C) signi= ficantly increases HSP70 (a key inducible protein) in monocytes.

=

  • Clinical observations in healthy young men = showed that a core temperature rise above 101.3°F (38.5°C) (reach= ing over 101.48°F (38.6°C)) during an initial sauna session induc= ed HSP72. However, heat acclimation by the 10th session limited the core te= mperature to 100.76°F (38.2°C), largely eroding the HSP response.=

  • Hot water immers= ion protocol targeting a rectal temperature of 103.1°F (39.5°C) f= or 60 minutes produced significant increases in both HSP27 and HSP70.

  • Heated exerc= ise protocols reaching 103.1°F (39.5°C) resulted in meaningful in= creases in HSP90, the initiator of the heat shock protein expression cascad= e

    3D""

Bryan Johnson is free today. But if = you enjoyed this post, you can tell Bryan Johnson that their writing is val= uable by pledging a future subscription. You won't be charged unless they e= nable payments.

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= 9; 2026 Bryan Johnson
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