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Limited evidenceGeneral health

C15 (Pentadecanoic Acid)

C15:0 is an odd-chain saturated fat from dairy that shows up in blood as a marker of dairy intake and correlates with lower diabetes risk in cohort studies. The leap from that correlation to 'the first essential fatty acid discovered in 90 years' is a marketing claim, not a proven one — no RCT has shown supplementing C15:0 improves a hard health outcome in humans.

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What the science says

  • Higher blood C15:0 predicts lower type 2 diabetes risk Moderate evidence

    A pooled analysis of 16 prospective cohorts (over 63,000 participants) found circulating C15:0 associated with a modestly lower incidence of type 2 diabetes, with hazard ratios around 0.80–0.90 per standard deviation. But C15:0 in blood is primarily a biomarker of dairy fat intake, so the association may reflect dairy consumption, or the dietary pattern around it, rather than the molecule itself.

  • C15:0 is an essential fatty acid Limited evidence

    A 2024 mini-review examined this claim directly and concluded the essentiality case is unsettled: humans synthesize small amounts of C15:0 endogenously, no deficiency syndrome has been defined, no requirement has been established, and no authority has classified it as essential. Calling it essential is a strong claim resting on cell-culture activity and observational associations.

  • Improves liver, metabolic or inflammatory markers Limited evidence

    Supporting data are dominated by cell-based assays, animal work, and studies in dolphins by the group commercializing the ingredient. Small human trials have reported changes in some blood markers, but there is no adequately powered, independent, placebo-controlled trial demonstrating clinically meaningful improvement in liver fat, HbA1c, or inflammation.

Dosage & safety

Studied doseCommercial products supply 100–200 mg/day of purified C15:0 (free fatty acid form), a dose derived from modeling rather than dose-ranging trials. For context, dietary intake from whole-fat dairy runs roughly 100–300 mg/day — meaning a serving or two of full-fat dairy delivers a comparable amount at a fraction of the cost.
SafetyNo meaningful toxicity signal at supplemented doses; it is a fatty acid found in ordinary food. Reported side effects are limited to occasional GI upset. Not banned in sport, no known drug interactions. The honest caution is financial rather than medical: it is one of the most expensive ways to consume a fat you can get from cheese, butter or whole milk, with less evidence than either fish oil or dairy itself.

How to take it

TimingTiming does not matter.
With food?With a meal containing fat, since it is a fatty acid.
Worth knowingA serving or two of full-fat dairy supplies a comparable amount of C15:0 for a tiny fraction of the price.

Frequently asked questions

Is C15:0 (pentadecanoic acid) an essential fatty acid?

Not established. A 2024 mini-review found the case for C15:0 being essential unsettled: humans make small amounts themselves, no deficiency syndrome or requirement has been defined, and no authority classifies pentadecanoic acid as essential.

Does C15:0 lower diabetes risk?

Higher blood C15:0 is linked to modestly lower type 2 diabetes risk in a pooled analysis of 16 cohorts (moderate evidence), but blood C15:0 mainly reflects dairy fat intake. That association does not show that a C15:0 supplement prevents diabetes, and no RCT has tested it on a hard outcome.

Is a C15:0 supplement worth it compared with eating dairy?

Probably not: C15:0 supplements supply 100-200 mg/day, while whole-fat dairy delivers roughly 100-300 mg/day, so a serving or two of full-fat dairy gives a comparable amount of pentadecanoic acid at a fraction of the cost. The supplement's liver, metabolic and inflammation claims have only limited evidence.

Does pentadecanoic acid have side effects?

C15:0 (pentadecanoic acid) shows no meaningful toxicity at supplemented doses, and reported side effects are limited to occasional GI upset, with no known drug interactions. Take it with a meal containing fat; timing does not matter.

Scientific references

Where to buy

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