Fatty15 is a longevity supplement by Seraphina Therapeutics built around a single active ingredient, C15:0 (pentadecanoic acid), which the brand markets as "the first essential fatty acid discovered in 90 years." The brand's underlying research originated from a US Navy-funded program studying healthy aging in dolphins.
But is C15:0 actually an essential fatty acid? Does Fatty15 use a research-backed dose? Are the brand's "clinically proven" claims supported by human clinical evidence? And is Fatty15 better or worse than other popular longevity supplements like Tru Niagen?
In this article we'll answer all of these questions and more, as we analyze the ingredients in Fatty15 to give our take on whether or not it's likely to be effective, and whether or not it's healthy.
We'll also share our concerns about the brand's central marketing claims, and compare Fatty15 to other popular longevity supplements to pick our winners (and losers).
Key takeaways:
- Clean single-ingredient formulation with a research-backed dose
- Marketing claims outrun the human RCT evidence
- We do not currently recommend Fatty15
Ingredient Analysis
The ingredients in Fatty15 are shown below:
image source: https://fatty15.com/
Pentadecanoic acid (C15:0), branded by Seraphina Therapeutics as FA15™, is the only active ingredient.
It's a saturated fatty acid found in small amounts in dairy fat that the brand markets as the first essential fatty acid discovered in over 90 years.
The largest independent trial, the TANGO study published in the American Journal of Clinical Nutrition, evaluated C15:0 in adults with fatty liver disease over 12 weeks.
The trial showed a numerical improvement in liver fat with C15:0, but the authors noted that baseline imbalances between groups precluded firm conclusions.
A separate clinical trial published in the Journal of Nutrition, did not show the weight-loss benefit it was designed to test, though it found modest improvements in some liver-health biomarkers.
Other published human trials have explored C15:0 supplementation for skin condition, blood pressure, and mood.
The independent observational literature is substantially larger, with dozens of studies broadly associating higher circulating C15:0 with lower cardiovascular and metabolic disease risk, although these are biomarker correlations rather than supplementation outcomes.
Unlike omega-3 fatty acids, which carry formal essential-fatty-acid status from major health authorities (as we documented in our fish oil supplements article), C15:0's classification as essential is a newer and still-debated hypothesis.
The inactive ingredients in this supplement should be safe and non-toxic.
Overall, we do not currently recommend Fatty15, because we can't identify any clinical evidence suggesting that its supplementation enhances longevity.
Does Fatty15 Cause Side Effects?
Unlike most supplements, Fatty15 has been studied for safety in multiple peer-reviewed human clinical trials, including the TANGO fatty-liver trial and the 2024 weight-loss trial we discussed in the Ingredient Analysis section.
Across those trials, C15:0 supplementation has not been associated with serious adverse events.
This makes biological sense.
Pentadecanoic acid is naturally present in dairy fat, and humans routinely consume it through cheese, butter, and milk products. The supplemental dose in Fatty15 is comparable to what regular dairy consumers obtain through diet.
Fatty15's active ingredient also holds GRAS (Generally Recognized as Safe) status with the US FDA, which is uncommon for a single-ingredient dietary supplement.
We do not consider Fatty15 likely to cause side effects in healthy adults, though as with any supplement, individuals with specific health conditions should consult their doctor before use.
Fatty15 vs. Longevity Supplements
Here's how Fatty15 compares to other popular longevity supplements in terms of formulation quality, in our opinion:
Urolithin A
Urolithin A is a postbiotic compound found in pomegranates and marketed by brands like Mitopure. It activates the body's process for clearing damaged mitochondria, and it's clinically shown to improve muscle strength and mitochondrial biomarkers in middle-aged adults.
While both supplements have clean formulations, urolithin A's human-trial evidence for its central claim is more conclusive than Fatty15's.
Urolithin A is the winner from a potential efficacy perspective.
Winner: Urolithin A
Tru Niagen
Tru Niagen is a popular NAD+ booster, nicotinamide riboside, and one of the most-researched longevity supplements on the market.
As we documented in our Tru Niagen review article, the brand has funded more clinical trials than nearly any other supplement we cover, with clinically proven effects on cellular NAD+ levels.
Both formulations are clean and well-dosed. Tru Niagen has the more robust clinical-trial portfolio for its primary mechanism.
Tru Niagen is the winner from a potential efficacy perspective.
Winner: Tru Niagen
Nordic Naturals
Nordic Naturals is a leading omega-3 fish oil brand. Unlike C15:0, omega-3 fatty acids (EPA and DHA) are formally classified as essential by major health authorities and have decades of human clinical research behind them for cardiovascular and anti-inflammatory benefits.
Both are fatty-acid supplements with clean formulations, but omega-3's evidence base is dramatically broader and more conclusive than C15:0's.
Nordic Naturals is the winner from a potential efficacy perspective.
Winner: Nordic Naturals
Fatty15 Pros and Cons
Pros:
- Clean single-ingredient formulation
- Research-backed C15:0 dose
- No flagged inactive ingredients
- Broad observational evidence base for C15:0
- Unlikely to cause side effects
Cons:
- Human RCTs have produced mixed or inconclusive results
- "Essential fatty acid" claim is contested in independent literature
- "Clinically proven" claim based on customer survey
- Less proven than some competitors
