C15:0 (Pentadecanoic Acid)
Odd-chain saturated fat linked to better metabolic and heart health in observational studies; supplement trials show minimal effect.
Summary
C15:0 is an odd-chain saturated fatty acid found mainly in full-fat dairy; observational studies link higher levels to lower diabetes, cardiovascular and overall mortality, though one study linked it to higher MCI risk and another found no mortality association. The two supplement trials she reviews showed minimal effects: a 200 mg/day trial lowered liver enzymes only in participants whose levels rose, and adding C15:0 to a Mediterranean-style diet slightly improved LDL. She disputes the manufacturer's claim that C15:0 is essential, citing evidence the body makes it from gut-microbe-derived propionate, and suggests full-fat dairy, resistant starch and inulin as ways to raise it.
Skeptical of the supplement's claims; suggests boosting production via full-fat dairy, resistant starch and inulin, and wants placebo-controlled trials.From C15:0 (Pentadecanoic Acid): Dietary Sources and Supplement Options
The evidence
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Human trial
In a 2024 trial of 30 overweight adults (partly funded by the manufacturer), 200 mg/day C15:0 vs placebo raised levels in only half of takers; those responders had lower liver enzymes, but there was no change in weight, blood pressure or cholesterol.
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Human trial
In 88 women in China with NAFLD, a Mediterranean-style diet plus C15:0 gave similar liver-fat reduction to diet alone, with extra LDL lowering and more Bifidobacterium adolescentis.
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Human trial
In a human clinical trial, seven days of inulin or propionate supplementation raised C15:0 levels by 13-17%, while cellulose (control) did not.
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Human obs.
Higher dietary intake of odd-chain fatty acids was associated with a 36% lower risk of mortality over 11 years in a large study.
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Human obs.
In contrast, a 2024 study of Chinese adults aged 45+ found higher C15:0 levels correlated with a 2-fold increased risk of mild cognitive impairment.
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Animal
In a mouse model of inflammatory bowel disease, C15 supplementation reduced inflammation and helped preserve gut barrier integrity.
Doses used in studies
Amounts reported in the research, not dosing recommendations.
| Dose | Context |
|---|---|
| 200 mg/day | 2024 placebo-controlled trial in 30 overweight adults |
| 100 mg/day (commercial Fatty-15 dose; about the C15:0 in 1.5 tablespoons of butter) | Product dose, not a study dose |
Cautions
- The 200 mg/day trial found no significant adverse events, so the supplement is likely safe at least short-term.
- Much of the published research comes from the manufacturer; she focused on studies not funded by a supplement company to avoid bias.
- C15:0 is not used in the body like DHA/EPA, so it should not be treated as a replacement for fish oil.