Hi Reader,

This week I'm publishing something I've been asked about for months but most physicians won't touch.

Grey market peptides.

The "research chemicals" currently flooding Silicon Valley. Tech workers mixing powders in their kitchens. Injecting themselves with insulin syringes ordered from Amazon. Attending "peptide raves" with mix-your-own workshops.

I'm not here to tell you not to do it. I'm here because people are doing it anyway—and information asymmetry gets people hurt.

This is a harm reduction guide. Not an endorsement.

The TL;DR if you only have 30 seconds:

• 💉 The Gray Market: We dive deep into the "Research Use Only" loophole, why "99% Purity" is a misleading metric, and the difference between a chemical reagent and a sterile drug.
• 🤖 AI Health Wars: ChatGPT Health wants to be your patient portal. Claude wants to be your chief medical officer. I tried both this week, and I definitely have a favorite.
• 😴 Sleep as Crystal Ball: Stanford's new AI predicts dementia, heart attacks, and death up to 25 years out—from a single night of sleep data.
• 🍳 Dietary Guidelines: The government finally admitted the food pyramid was wrong. Full-fat dairy is back. Now they just need to fix the labels.

Let's get into it.

💉 99% Pure ≠ Safe: A Physician's Guide to Gray Market Peptides

The New York Times just covered the gray market peptide boom. It's officially mainstream.

But the media coverage usually misses the nuance. It treats users like reckless junkies, ignoring the very real economic and medical drivers pushing people toward these "research chemicals."

The Promise: Why Intelligent People Take the Risk

I understand why this market exists. The traditional medical system has gaps, and patients are falling into them.

• For the injured athlete: Standard care is often "rest and ibuprofen." Peptides like BPC-157 offer the promise of active tissue repair.
• For the weight loss patient: If insurance denies coverage for Zepbound ($1,300/month), purchasing semaglutide direct from a lab for one-fifth the cost feels like a financial lifeline.
• For the chronic fatigue sufferer: When medicine offers only dismissal, peptides like MOTs-C and SS-31 offer a potential mechanism for recovery.

The desire for autonomy is valid. But if you step into this world, you must understand the difference between a patient and a "researcher."

The "Research Use Only" Loophole

Every vial on the gray market is labeled RUO (Research Use Only). This is, essentially, a legal fiction. It is a pinky-swear between you and the vendor that says: "I am a researcher. This is a chemical reagent. I will not put this in a human body."

But of course, the biohackers purchasing these RUO peptides do indeed put them in their bodies, at their own risk.

That label is how vendors bypass the FDA. It shifts 100% of the liability to you.

The Purity Trap: Why 99% Doesn't Mean Safe

This is where I see smart people make the biggest mistake. You buy a vial, send it to a third-party tester like Janoshik or Finnrick, and get a report saying "99.5% Purity." You feel safe.

You shouldn't. Purity tests only confirm identity (is it semaglutide?). They rarely test for sterility or endotoxins. You can have a vial of 99.9% pure peptide that is contaminated with bacterial byproducts from a dirty lab. Injecting that can lead to sepsis or anaphylaxis.

Gray Market vs. Compounding Pharmacies: The Critical Difference These two are often confused, but they are not the same.

• Compounding Pharmacies (503A/B): These are licensed, regulated facilities. They require a prescription. They are inspected by state boards. They are required to maintain sterility standards.
• Gray Market Vendors: These are websites that ship "chemicals" to anyone with a credit card. No prescription. No inspections. No accountability.

The "Category 2" Warning: Be careful. The FDA recently moved peptides like BPC-157 to "Category 2," meaning legitimate pharmacies can no longer compound them. If a "pharmacy" is selling you injectable BPC-157 today, they are likely ignoring FDA regulations—which means they might be ignoring safety regulations, too.

​Read the Full Guide ​

In the full article, I break down:

• The "Risk Hierarchy" of delivery routes (why nasal sprays are riskier than you think).
• The specific testing protocols sophisticated users follow.
• The "Sacrificial Vial" problem.

🤖 The AI Health Wars: Smart Brains, Broken Pipes

I spent the weekend stress-testing the new health features from both OpenAI and Anthropic. They launched within days of each other, promising to revolutionize how we interact with our medical data.

The Strategy: Two Different Visions

• ChatGPT Health wants to be your Universal Patient Portal. It’s aggregating everything—Apple Health, Epic records via b.well, and wearables—into one mass-market feed.
• Claude for Healthcare wants to be your Chief Medical Officer. It is targeting the "power user," integrating deep with Function Health and structured data to give high-fidelity analysis.

The Reality: The Plumbing is Broken The marketing promised a revolution. My weekend testing revealed a beta.

It turns out the weak link isn't artificial intelligence anymore. We’ve solved reasoning. We haven't solved connection.

My experience with both platforms was defined by friction:

• The "Eternal Loading" Loop: Integrations that were supposedly synced kept timing out when I actually asked a question.
• The Apple Health Lag: ChatGPT took over 24 hours to index my Apple Health data. In the age of real-time AI, waiting a day for your step count to sync feels archaic.
• The Data Gap: The Function Health integration—which was the headline feature—was surprisingly opaque. It gave me the number of abnormal biomarkers but struggled to pull the raw data for analysis.

🛠️ Want to test the plumbing yourself?

If you want to try breaking these integrations yourself (or see if your doctor's office is one of the lucky ones that actually syncs), here is where they hid the settings:

For ChatGPT (OpenAI):

1. Go to Settings (bottom left) → My Health.
2. Click "Connect Health Data" (powered by b.well).
3. Search for your hospital system or Function Health credentials.
   • Pro-tip: If you don't see the setting, try typing "Connect my medical records" directly into the chat window to trigger ChatGPT to walk you through the steps.

For Claude (Anthropic):

1. Click your Initials in the bottom left corner in the sidebar.
2. Select Settings → Connectors → Browse Connectors.
3. Find HealthEx and click "Connect."
   • Note: This is also where you’ll link Function Health. (Apple/Android Health support is rolling out in this same menu later this week).

The Bottom Line: This will only get better. But for now, I expect most people will continue to copy and paste directly into their AI chats!

😴 Your Sleep Is a Crystal Ball (Stanford’s AI)

A single night of sleep can predict your risk of dying years in advance.

Stanford researchers just published a massive paper in Nature Medicine that changes how we view sleep. They built an AI called SleepFM, trained it on 585,000 hours of sleep data from 65,000 people, and asked a simple question:

What can the conversation between your brain, heart, and lungs tell us about your future?

The Results are Fascinating

From a single night of data, the AI predicted future disease with startling accuracy (C-Index):

• Dementia: 85% accuracy
• All-Cause Mortality: 84% accuracy
• Heart Failure: 80% accuracy
• Parkinson’s: 89% accuracy

Can we soon use a night of sleep to discover these tough-to-diagnose conditions?

The "Discord" Signal

The most fascinating finding wasn't a specific biomarker. It was synchronization.

Your organs are supposed to talk to each other. When you enter deep sleep, your heart rate should drop, your breathing should stabilize, and your brain waves should slow down—all in unison.

SleepFM found that discord is a predictor of disease. When your brain signals "deep sleep" but your heart acts like it’s stressed, that mismatch predicts disease years before symptoms appear.

The Takeaway: We used to think sleep studies were just for finding apnea. This paper suggests they are actually a window into your entire biological trajectory.

The future of longevity isn't just tracking how long you sleep. It's measuring how well your organs dance together while you’re unconscious.

🍳 The Food Pyramid Was Wrong (Finally)

The new U.S. Dietary Guidelines are out—and for the first time in nearly half a century, federal policy is admitting what longevity physicians have argued for years.

The big shifts:

• Full-fat dairy is back. The war on butter is officially over.
• Protein targets are up.
• Processed food is the actual enemy.

The gut health section is actually good, and the anti-processed food stance is overdue.

My only gripe? Guidelines only matter if people can act on them. Our nutrition labels are still stuck in 1990—focused on "calories" and "fat" rather than "processing methods" or "additives." We updated the guidelines; now we need to fix the label.

🗣️ The Debate: One Size Does Not Fit All

I posted about this on LinkedIn, and the comments section turned into a fascinating debate. It highlighted exactly why "Federal Guidelines" will always struggle: Biology is individual.

Three specific points from the community that added necessary nuance:

• Genetics matter more than pyramids. Dr. Joseph Raffaele correctly pointed out that while "butter is back" generally, it isn't for everyone. If you carry the ApoE4 gene (like ~25% of the population), high saturated fat intake drives up Alzheimer's risk. A 200lb athlete and a 120lb ApoE4 carrier should not be eating the same diet.
• The "Blue Zone" Tension. Steve Ardire and Matthew Amsden noted the disconnect between these new meat-heavy guidelines and Blue Zone data, where meat is a treat, not a staple. The tension between "ancestral/carnivore" data and "epidemiological/plant-based" data remains the biggest wedge in longevity.
• The "Hidden" Processing.Toni Maraviglia highlighted the issue of "immune triggers" like emulsifiers (xanthan gum) and "natural flavors" that hide in seemingly healthy organic foods. It’s not just about macros; it’s about the additive load.

The takeaway? Government guidelines are a start, and a better one than before. They are designed to prevent deficiency in the average American. They are still not designed to optimize longevity for you, so take it all with a (metaphorical) grain of salt!

⚡ Longevity Quick Hits

The Science

🦠 CAR-T Cells Repurposed for Aging Usually a cancer treatment, CAR-T therapy was engineered by Cold Spring Harbor labs to hunt "zombie" (senescent) cells in the gut. A single dose in mice restored the gut barrier and nutrient absorption for over a year. The "living drug" approach to longevity is here.

👁️ Reversing "Irreversible" Blindness USC launched a Phase 2b trial for a bioengineered retinal patch. Unlike electronic chips, this is a layer of stem cells that replaces dead tissue in Dry Macular Degeneration. In early trials, 27% of patients actually regained vision—a massive deal for a condition previously thought untreatable.

🧬 The Supercentenarian Secret It’s not just luck; it’s aggression. A study of 110+ year-olds found they possess rare "killer" CD4+ T-cells that younger people don't have. They don't just "avoid" decline; their immune systems actively adapt to become more aggressive against disease as they age.

Industry Pulse: JPM26 Updates

The biggest healthcare conference of the year (JPM) is happening right now. Here are the three updates that matter.

🤖 The $1B "Lab-in-the-Loop" NVIDIA and Eli Lilly announced a massive partnership today. Lilly is building a physical lab where robots run experiments, feed data to NVIDIA’s AI, and the AI designs the next experiment overnight. The wet lab is officially going AI.

🐶 First Longevity Drug... For Dogs Loyal confirmed their life-extension pill for senior dogs is on track for a 2026 launch. Why you should care: The FDA accepted "lifespan extension" as a valid endpoint for this trial, setting the regulatory precedent for human longevity drugs.

Where You Can Find Me

Is Longevity Medicine a Bubble in 2026? Live discussion with Dr. Hillary Lin & Dr. Anant Vinjamoori – Join us virtually on LinkedIn Jan 14, 2026 @ Noon EST!

Physician Creator Trends – VSP Innovation Center & Matter Fireside Chat (Virtual) – Jan 28 @ 1PM EST link here. So excited about this topic!

Longevity: Living Longer, Living Better? Join myself and fellow longevity doctor Mishal Reja, MD in NYC for this intimate salon at Extension Health!

👱🏻‍♀️👩🏻‍🦰👩🏻👧🏽👧🏾 Livelong Women’s Health Summit – April 17-18, 2026, SF, CA. Delighted to join 50 other thought leaders in speaking on women's longevity!​

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​GlycanAge measures your immune system's biological age, offering an easy way to detect "inflammaging" and recommend how to fix it.

Navigating the Wild West

If there is a theme to this week's issue, it is autonomy.

You are parsing your own sleep data. You are evaluating gray market compounds because the insurance system failed you. You are rewriting your diet before the nutrition labels catch up.

We are entering an era where the patient is moving faster than the system. It is a powerful place to be, but it is a noisy one.

My goal for 2026 is to ensure that "autonomy" doesn't turn into "anarchy." We want the results, not the reckless risks.

Stay safe, stay curious.

Hillary Lin, MD

Co-Founder & CEO

​Care Core​

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Follow me for more longevity insights: YouTube | LinkedIn | Instagram | TikTok​

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