Before You Try Peptides

Same Evidence, Different Conclusions

By Lori Finlay, NP, CNS

  This is Part 3 of a three-part series on peptides. Part 1 covered the foundation. Part 2 covered the science, largely through Dr. Elizabeth Yurth’s framework shared at the Beyond Biohacking Conference. This part brings in another respected, equally experienced perspective — because you deserve to see the full conversation.

I want to start this one differently.

Dr. Elizabeth Yurth uses peptides in her practice every day. Twenty years of clinical experience. Real patients. Real outcomes.

Dr. Ben Lynch will not use peptides. At all. He has studied epigenetics and cell signaling for two decades, and his answer is still no.

Both of these people are brilliant. Both have earned the right to their conclusion. And I think you deserve to hear exactly why they disagree — not a watered-down version, not my opinion dressed up as theirs. The real argument.

Who Is Dr. Ben Lynch

Dr. Lynch is a naturopathic physician and the author of Dirty Genes. He has spent his career studying MTHFR, methylation, and how genes get switched on and off — the field called epigenetics.

He is not anti-science. He is not a fear-monger. He is, if anything, one of the most detail-obsessed clinicians in the functional medicine space. And that is exactly why his caution matters.

This Is Epigenetics at Its Core

Here is the part I most want you to sit with.

Dr. Lynch does not say peptides are fake, or that they do nothing. He says the opposite.

“They work.” — Dr. Ben Lynch

That is his concern. Not that peptides are inert — that they are powerful. Peptides act as genetic switches. They influence DNA methylation, histone structure, and microRNA signaling — the machinery that decides which genes get turned up and which get turned down inside your cells.

This is not one gene, one effect. A single peptide can influence dozens of genes simultaneously, across multiple systems in your body. That is not a small thing. That is upregulating and downregulating your own genetic expression — in real time.

Here is where Dr. Lynch and Dr. Yurth actually agree, even though their conclusions differ: peptides are not gentle background noise. They are genuinely epigenetically active. Dr. Yurth sees that power as the reason to use them thoughtfully. Dr. Lynch sees that same power as the reason to be extremely careful.

Both of them are responding to the same fact. They just weigh the risk differently.

The Debate Playing Out in the Actual Research

This is not just Dr. Lynch’s opinion versus Dr. Yurth’s opinion. This disagreement is happening in the published literature itself — in real time, this year.

A 2025 paper in the journal Pharmaceuticals raised a specific concern about BPC-157: its effect on angiogenesis, the process of growing new blood vessels. [1] The concern is that the same VEGF pathway BPC-157 activates to heal tissue is the same pathway tumors use to grow their own blood supply. The theoretical worry is that a peptide which helps a torn tendon heal faster might also, in someone with an undetected tumor, help that tumor grow.

The scientists who originally discovered BPC-157 published a direct rebuttal. They pointed to decades of animal safety data, argued the anti-tumor evidence is actually stronger than the pro-tumor concern, and pushed back hard on the angiogenesis-to-cancer leap.

A third group then responded to that rebuttal, noting that over 80% of all published BPC-157 research comes from the same original research team — which makes independent verification harder to find. This is not me taking a side. This is the actual scientific conversation happening right now, argued by credentialed researchers in a peer-reviewed journal.

No study has confirmed that BPC-157 causes cancer in humans. But the mechanism for concern is real, and independent replication is still thin.  That is the honest state of the science — not settled in either direction.

A Concrete Example: Melanotan II

I did not cover this peptide in Part 2, and I want to correct that now, because it provides a clear illustration of what “it depends on your picture” actually means in practice.

Melanotan II stimulates melanin production — it darkens your skin without sun exposure. It also, mechanistically, stimulates melanocyte activity broadly, including in existing moles.

Case reports exist of new moles, darkened moles, and melanoma (although rare) developing in people using it. Causation has not been proven. But the concern is not theoretical noise — melanocyte stimulation and melanoma risk are mechanistically connected in ways that make caution appropriate, especially for certain people.

If you have a personal or family history of melanoma, dysplastic nevi, or a large number of moles — avoid this one!

This is exactly the kind of nuance that gets lost when peptides get talked about as a single category. “Are peptides safe” is the wrong question. The right question is always: this peptide, for this mechanism, in this body, with this history.

How I Actually Think About This

I want to bring in something Dr. Yurth said that I have not been able to stop thinking about.

Most medical guidelines worldwide are built on Level B or Level C evidence — not perfect randomized trials.  Handwashing. Antibiotics. Cardiac care. All of these began with careful observation, long before the gold-standard studies caught up.  — Dr. Elizabeth Yurth, MD

This is true, and it matters. A huge amount of what we call good medicine today started as what doctors now call off-label use — a treatment used for a purpose the formal trials had not yet confirmed, because a thoughtful clinician connected the dots between mechanism, observation, and patient need, and moved forward carefully.

That is not reckless. That is how medicine has always advanced, in every era, including right now. It takes a clinician willing to sit with incomplete data, weigh the mechanism honestly, and proceed with real caution — not certainty, caution.

The difference between that and recklessness is entirely in the caution part.

My Bottom Line

Here is where I have landed, holding both Dr. Yurth’s clinical experience and Dr. Lynch’s caution at the same time.

1.     Start with the science. Not hype. Not fear. The actual mechanism, the actual research, the actual gaps in that research.

2.     Know your DNA. I highly advise this, though I do not require it of every client. Genetic variants — detox pathways, methylation status, cancer-related SNPs — change how appropriate any given peptide is for your specific body. To get truly precise care, and to optimize your physiology and gene expression, DNA testing helps us know what is actually going on underneath the surface. That is how you create the vitality you crave, deliberately rather than by guesswork.

3.     Get real screening. Not assumptions. Actual testing. I recently completed a Cancerguard multi-cancer early detection blood test myself — that kind of information changes the risk calculation entirely, in either direction.

4.     Consider your whole picture. A woman with a clean, anti-inflammatory diet, an active lifestyle, no concerning family history, and negative cancer screening is in a genuinely different risk category than a woman without those things. This is not one-size-fits-all medicine, and anyone who treats it that way — in either direction — is not being honest with you.

5.     Work with a real professional. Not a “bro” influencer selling vials on the internet. Not an AI chatbot. A licensed clinician who knows your history, your labs, and your genetics, and who is willing to say “I don’t know yet” when that is the honest answer. No offense to the tools — they have their place. But your body is not a place for guesswork.

Peptides are epigenetically powerful. That is exactly why they deserve respect, not hype and not fear.  Start responsibly. Know your DNA. Work with someone who knows what they are looking at.

Dr. Yurth is brilliant, and I meant that when I said it in Part 2. Dr. Lynch is equally brilliant, and his caution is not the opposite of good medicine — it is part of it.

You do not have to choose a side. You have to choose a clinician who will look at your actual picture and tell you the truth about it.

A quick note on my own role: I do not currently prescribe peptides myself. What I do is help you understand your genetics, your labs, and your full health picture — the precision work that needs to happen before anyone decides whether peptides make sense, and with whom.

  Consider This

• Do you know your genetic picture — your methylation status, your detox pathways, any cancer-related variants? This information changes which peptides make sense for you specifically.
• Have you had appropriate cancer screening for your age and risk profile? This matters more with any epigenetically active intervention, not less.
• Is your foundation — diet, movement, stress, toxin load — actually solid? That was Part 1‘s whole point, and it has not changed.
• Book your Free Vitality Assessment Call at ConsultLori.com. Let’s look at your full picture — genetics, history, and goals — together.

For the women who refuse to let their lifespan outrun their vitality span,

Lori Finlay, NP, CNS

References

References are cited in APA 7th edition format. Sources cited multiple times retain their original reference number throughout.

1.  Józwiak, M., Bauer, M., Kamysz, W., & Kleczkowska, P. (2025). Multifunctionality and possible medical application of the BPC 157 peptide — literature and patent review. Pharmaceuticals, 18(2), 185.

2.  [No authors listed]. (2025). The efficacy and safety of thymosin α1 for sepsis (TESTS): Multicentre, double blinded, randomised, placebo controlled, phase 3 trial.

3.  Nelson, S., Poddar, S., & Lin, T. J. (2012). Systemic toxicity associated with self-administration of melanotan II.

4.  Lynch, B. (2026). Peptides, epigenetics, and why I don’t use them [Video presentation]. Publicly available online.