What it's actually good for
Fatty15 is a purified supplement of pentadecanoic acid (C15:0), an odd-chain saturated fatty acid found in trace amounts in dairy fat, ruminant meat, and some fish. The company behind it, Seraphina Therapeutics, markets it as "the first essential fatty acid discovered in over 90 years" — a claim that originated from veterinary researcher Stephanie Venn-Watson's observation that C15:0 levels tracked with health status in aging Navy dolphins.
That's a genuinely interesting origin story. It is not, on its own, evidence that healthy adults are deficient in C15:0 or that supplementing it improves health outcomes. Worth knowing upfront: Venn-Watson co-founded Seraphina Therapeutics and, along with co-author Nicholas Schork, holds exclusive licensing rights from the U.S. Navy to commercialize odd-chain fatty acids. Most of the published research arguing C15:0 is "essential" comes from papers these two authored. The National Academies of Sciences, Engineering, and Medicine — the body that actually sets essential-nutrient classifications — does not recognize it as one.
What the research says
Essentiality claim (Grade C). The core marketing claim rests mainly on cell-based assays and observational associations published by the company's own founders, not on the kind of dietary-deprivation or requirement studies that established omega-3 and omega-6 as essential. No independent group has proposed reclassifying C15:0.
Cardiovascular benefit (Grade C). This is where independent data actually exists, and it's unflattering. A 2026 analysis of the CARDIA and ARIC cohorts — over 7,000 participants, funded by the NHLBI with no Seraphina involvement — found only modest links between plasma C15:0 and blood pressure, no association with cardiac function or cardiovascular events, and no causal effect in Mendelian randomization analysis. The authors' interpretation: C15:0 looks like a marker of an already-healthy diet, not an active ingredient. The one industry-partnered RCT built around cardiometabolic outcomes (TANGO, 88 women with fatty liver disease) found C15:0 added a small LDL reduction on top of a Mediterranean-style diet — but no advantage over diet alone on weight or liver fat.
Metabolic and liver markers (Grade C). The only pilot RCT testing the supplement in isolation (30 young adults, 200 mg/day, 12 weeks) found no change in weight, cholesterol, glucose, or inflammation versus placebo. A liver-enzyme benefit turned up only in the subgroup whose blood levels crossed a specific threshold — a secondary, post hoc finding in a 20-person treatment arm, not something a larger trial has confirmed.
How much, and which form
Fatty15's product delivers 100 mg/day. The lone dedicated RCT used 200 mg/day. Neither number comes from an established dose-response relationship — there isn't one yet.
Safety & interactions
Trials of up to 12 weeks in small samples (n=30-88) reported no significant adverse events, and the ingredient has cleared FDA's GRAS notification process. That's a low bar: it means no evidence of near-term harm, not confirmed long-term safety. This is informational, not medical advice — talk to a clinician before starting, especially if you're managing cardiovascular risk.
How we picked the brand
There is effectively one option: Fatty15 is the only purified, single-ingredient C15:0 product with any clinical data behind it. Listing it here is a statement of market reality, not an endorsement of the "essential fatty acid" framing — treat the underlying science as unsettled until independent groups replicate it.