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Pentadecanoic acid (C15:0)

Fatty acid · C15:0, C15, Pentadecanoic acid, Fatty15

Pentadecanoic acid, C15:0 for short, is a saturated fatty acid from milk fat that is marketed as a new “essential” fatty acid and longevity substance. Behind it are observational data that deserve to be taken seriously: people with more C15:0 in their blood develop type 2 diabetes less often. As a supplement, however, it has so far been tested in only two small studies over twelve weeks, and a genetic analysis argues against a causal effect on blood pressure.

What pentadecanoic acid is

Pentadecanoic acid is a saturated fatty acid with 15 carbon atoms, that is, with an odd chain length. It occurs in trace amounts in milk fat and in some fish and plants (Venn-Watson 2020). In the blood, it is considered a marker of how much milk fat someone eats (Trieu 2021). As a supplement, it is sold under the brand name Fatty15, among others.

The idea of classifying C15:0 as an essential fatty acid comes from the researcher Stephanie Venn-Watson. According to the conflict-of-interest statements in her papers, she is a co-founder of Seraphina Therapeutics, which holds the US Navy’s exclusive license rights to market odd-chain saturated fatty acids.

In the BK-Score, human evidence stands at 3 out of 10 points. This axis rates the state of knowledge, not the substance. The longevity promises rest on cell experiments, animal experiments and observational data, not on intervention studies in humans.

How it works

In human cell systems, C15:0 showed dose-dependent activities in 10 of 12 systems, including anti-inflammatory and antifibrotic ones; at 17 µM it shared 24 activities with rapamycin. The authors describe that C15:0 activates the enzyme AMPK and inhibits mTOR, two central metabolic switches associated with longevity (Venn-Watson 2023). In obese mice on a high-fat diet and in rabbits on a high-fat, high-cholesterol diet, C15:0 dampened inflammation, anemia, dyslipidemia and fibrosis (Venn-Watson 2020).

A plausible mechanism in cells and animals is not yet a benefit in humans. Both papers come from co-founders of the manufacturer; an independent confirmation of the cell findings does not exist in the sources reviewed here.

What is well supported

  • Observational data on diabetes with moderate certainty. In a meta-analysis of prospective cohort studies, a C15:0 proportion in plasma phospholipids and red blood cells that was 0.1 percentage points higher was associated with a lower risk of type 2 diabetes (relative risk 0.68), with moderate certainty of evidence (Schaefer 2026).
  • Less cardiovascular disease in cohorts. Across 18 observational studies, the risk in the highest versus the lowest third of C15:0 levels was 0.88 (Trieu 2021).
  • The blood level can be raised. 12 weeks of supplementation increased the C15:0 level by 1.88 µg/ml compared with placebo, without meaningful adverse events (Robinson 2024).
  • An LDL effect in a randomized study. In the TANGO study, C15:0 in addition to a diet lowered LDL cholesterol more than the diet alone (Chooi 2024).

What the studies show

First randomized study: Robinson 2024

In a double-blind study, 30 young adults with overweight or obesity, 20 years old on average, received 200 mg of C15:0 (20 people) or placebo (10 people) for 12 weeks. The primary endpoint, the rise in blood level, was met: 1.88 µg/ml more than under placebo. Half of those treated reached more than 5 µg/ml; in them, the liver values ALT fell by 29 and AST by 6 U/l more, and hemoglobin rose more than in those treated who stayed below this value. That is a comparison within the treatment group, not a comparison with placebo. The manufacturer supported the study and provided the study product and placebo.

Fatty liver: the TANGO study

Chooi 2024 divided 88 Chinese women with non-alcoholic fatty liver, double-blind, into three groups: a Mediterranean-style diet adapted to Asian cuisine with C15:0, the same diet without C15:0, or their usual diet, each for 12 weeks. Both diet groups lost more weight and liver fat than the control group: 4.0 kg and 33 percent liver fat with C15:0, 3.4 kg and 30 percent without. C15:0 additionally lowered LDL cholesterol and increased the proportion of Bifidobacterium adolescentis in the gut.

Cohort studies: diabetes and heart

Schaefer 2026 analyzed 27 publications of prospective cohort studies on fatty acid biomarkers. For C15:0 in plasma phospholipids and red blood cells, the relative risk of type 2 diabetes was 0.68 (0.56 to 0.81) per 0.1 percentage point higher proportion, with moderate certainty of evidence. Trieu 2021 found, in a Swedish cohort of 4,150 adults over a median of 16.6 years, a lower cardiovascular risk with higher C15:0 (hazard ratio 0.75), and 0.88 in the meta-analysis across 18 studies. In the meta-analysis there was no association with all-cause mortality.

Cause or companion: Steffen 2026

Steffen and colleagues examined the associations in the US cohorts CARDIA with 3,196 and ARIC with 3,889 people. Higher C15:0 was associated with slightly lower blood pressure and less frequent hypertension (hazard ratio 0.86), but not with new cardiovascular disease or with heart function on ultrasound. A Mendelian randomization, which uses genetic differences as a natural experiment, found no indication of a causal effect on blood pressure, resting heart rate or hypertension. The authors consider the overall data incompatible with a causal cardiovascular benefit.

Where the data stop

  • Longevity and aging. The comparison with rapamycin and metformin comes from cell cultures. No aging or lifespan endpoint has been studied in humans.
  • Causal benefit. The cohort data cannot separate whether C15:0 itself acts or indicates milk fat intake and lifestyle. For blood pressure, the genetic analysis argues against a cause.
  • Hard endpoints. No intervention study has measured diabetes, heart attack or mortality. The two randomized studies lasted 12 weeks and measured blood level, liver values and blood lipids.
  • Independent studies. The cell and animal experiments come from co-founders of the manufacturer. A study on red blood cells and biological aging in 93 older adults is registered but, according to the registry, is not due to start until 2027 (NCT07812792).

Status, approval and legal

Pentadecanoic acid is a natural component of milk fat. As an isolated substance, it is not on the EU’s Union list of authorized novel foods (Implementing Regulation 2017/2470, consolidated version of August 10, 2026). We found no authorization or entry in the EU Novel Food Catalogue for isolated pentadecanoic acid. Whether a product may be marketed in Germany therefore depends on whether the substance was consumed as food to a significant degree before May 1997; we found no evidence of this for isolated C15:0.

There are no authorized health claims for pentadecanoic acid; the EU list under Regulation 432/2012 contains no entry for it.

Safety

In the Robinson 2024 study, no meaningful adverse events occurred over 12 weeks. Longer data in humans do not exist, nor do data on pregnancy, breastfeeding and children. The TANGO study reports no safety data in the abstract. In the BK-Score, safety stands at 2 out of 10 points; this axis measures how well safety has been studied, not how safe the substance is. This text is information and does not replace medical advice.

BK-Score Hype far ahead of evidence

Human evidence3
Mechanism4
Safety data2
Hype gap2
Track record of use2

Evidence 3, because there are only two small randomized studies over 12 weeks: in Robinson 2024 (30 participants), the increased blood level was the primary endpoint, and better liver values appeared only within the treatment group; in the TANGO study (88 women with fatty liver), C15:0 in addition to diet lowered LDL. The favorable associations with diabetes and cardiovascular disease come from observational studies (Schaefer 2026, Trieu 2021), and a Mendelian randomization found no causal effect on blood pressure (Steffen 2026). Mechanism 4, because AMPK activation, mTOR inhibition and anti-inflammatory effects have been shown in human cell systems and in mice and rabbits, mostly by co-founders of the manufacturer. Safety 2, because human data are available from only two studies over 12 weeks. Hype 2, because C15:0 is marketed as an essential fatty acid and a longevity substance on a par with rapamycin, while no hard endpoint has been studied in humans. Use 2, because isolated pentadecanoic acid has been sold as a supplement for only a few years. Direction open: too few intervention data for a verdict.

The score rates the state of knowledge, not the substance. “Safety data 9” means well studied – not harmless. “Track record of use 9” means used long and widely – that is not proof of efficacy.
Subjective assessment by Biohacking Kompakt based on published scoring rules – not a scientific rating and not a medical recommendation. Rules and all ratings (German)

Frequently asked questions about pentadecanoic acid (C15:0)

What is pentadecanoic acid (C15:0)?

A saturated fatty acid with 15 carbon atoms that occurs in trace amounts in milk fat and in some fish and plants. In the blood, it is considered a marker of milk fat intake. As a supplement, it is marketed as a new essential fatty acid.

Is C15:0 an essential fatty acid?

That is a proposal by the researcher Stephanie Venn-Watson, co-founder of the manufacturer, based on cell and animal experiments and observational data. What has been shown in humans so far is that supplements raise the blood level. Whether a low level causes disease is open; a genetic analysis found no causal effect on blood pressure.

Does C15:0 lower the risk of diabetes?

In observational studies, people with higher C15:0 levels had type 2 diabetes less often, with moderate certainty of evidence. No study has tested whether a supplement lowers the risk. The higher levels may also stand for more milk fat and a different lifestyle.

What do the studies with C15:0 capsules show?

There are two randomized studies over 12 weeks. In 30 young adults, the blood level rose; better liver values appeared only in those treated who reached a high level. In 88 women with fatty liver, C15:0 in addition to diet lowered LDL cholesterol.

Is C15:0 allowed in Germany?

Pentadecanoic acid is not on the EU’s Union list of authorized novel foods. We found no authorization or entry in the Novel Food Catalogue for the isolated substance. There are no authorized health claims.

Is C15:0 safe?

In the study with 30 participants, no meaningful adverse events occurred over 12 weeks. Longer data in humans are lacking, as are data on pregnancy, breastfeeding and children. In the BK-Score, safety data therefore stand at 2 out of 10 points.

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Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in the hands of a physician. Last updated: 2026-10-07.