NAD+ and cancer: what TikTok pharmacists get wrong

What did @darya.only.one actually say?

Dr. Daria, a pharmacist, made two separate arguments in this video. First, she warned that unregulated NAD supplements sold online may not contain what they claim, and could include toxic, unlisted ingredients. Second, she said she personally avoids recommending NAD to patients because it could cause "microscopic cancer cells" to "proliferate and grow more rapidly." She also gave a reasonably accurate explanation of first-pass metabolism to explain why injectable NAD delivers more of the active compound to the bloodstream than oral forms. These are three distinct claims, and they deserve to be evaluated separately, because they are not equally solid.

Does the science back up the cancer proliferation concern?

Partially, but the framing is more alarming than the evidence warrants. The relationship between NAD+ and cancer is genuinely complicated, and Dr. Daria is not making this up. However, presenting it as a straightforward danger for general consumers oversimplifies a contested area of research.

NAD+ is a coenzyme involved in DNA repair, energy metabolism, and cellular survival signaling. Some cancer biology research has found that certain tumors upregulate NAD+ biosynthesis pathways to fuel rapid cell division. Specifically, NAMPT (nicotinamide phosphoribosyltransferase), a key enzyme in NAD+ synthesis, is overexpressed in several cancer types, which is why NAMPT inhibitors have been studied as potential oncology agents (Garten et al., 2015, Trends in Pharmacological Sciences).

But here is where the picture gets murkier. A 2021 review in Frontiers in Oncology (Luongo et al.) noted that NAD+ has dual roles in cancer: it can support tumor cell survival in some contexts, but it also supports immune surveillance and DNA repair mechanisms that may actually suppress cancer initiation. The idea that supplementing NAD+ in a healthy person with "microscopic cancer cells" will reliably accelerate tumor growth is not established by clinical evidence. This is a plausible mechanistic hypothesis, not a proven clinical risk.

What did she get right, and what deserves more nuance?

The supplement quality warning is accurate and underappreciated. Studies on dietary supplement adulteration are consistent on this point. A 2023 analysis published in JAMA Network Open found that a meaningful proportion of tested supplements did not match their label claims for active ingredient concentration. For NAD precursors specifically, third-party testing has documented wide variance in NMN and NR product potency. Dr. Daria is correct that buying unregulated supplements online carries real quality and safety risks.

Her first-pass metabolism explanation is also basically correct. Oral bioavailability of NAD precursors like NMN and NR is affected by gut metabolism before systemic absorption, though some research suggests NR and NMN can reach circulation intact to a meaningful degree (Trammell et al., 2016, Nature Communications). The injectable versus oral distinction is legitimate pharmacokinetically.

Where she deserves pushback is the absolutism. Saying "I do not recommend NAD for patients" as a blanket policy based on a theoretical cancer risk, without acknowledging that the clinical evidence for harm in healthy adults is thin, goes further than the current data supports. It may also discourage people with legitimate interest in NAD research from having a more nuanced conversation with their own providers.

What should you actually know?

The NAD-cancer relationship is an active research area, not a settled danger signal. If you have an active cancer diagnosis or a strong family history, the theoretical concern about NAD+ supplementation is worth discussing with your oncologist before starting anything. That is a reasonable clinical caution.

For healthy adults without a known cancer diagnosis, the current human trial data does not establish that NAD supplementation accelerates tumor growth. Most clinical trials on NMN and NR in humans have been short-duration safety and pharmacokinetic studies, and none have reported tumor promotion as an adverse event. The longest and most cited trials include Yoshino et al. (2021, Science) on NMN in postmenopausal women, which did not flag cancer-related signals.

The supplement quality concern is the more immediately actionable warning from this video. If you are going to use any NAD precursor, buying from a source with verified third-party testing (USP, NSF, or Informed Sport certification) materially reduces the risk of getting a product that is mislabeled, underdosed, or contaminated.

• NAD+ precursors are not FDA-approved treatments for any condition.
• Compounded injectable NAD formulations are not equivalent to any approved pharmaceutical product.
• No dose of NAD supplementation should be interpreted from this article or the original video as a recommendation.