Pentadecanoic acid (C15) is a saturated odd-chain fatty acid found naturally in full-fat dairy products and ruminant fats. A small group of researchers, primarily affiliated with Epitracker, has proposed it may support cellular health through mechanisms including integration into cell membranes, partial activation of PPAR-alpha and PPAR-delta receptors, and potential reductions in ferroptosis and cellular senescence.[1] This hypothesis has not yet been formally adopted by mainstream nutrition science or any regulatory body.
As consumer interest grows, the supplement market has filled with products of varying quality, dosing, and transparency. Because the FDA has not evaluated C15 for the treatment or prevention of any disease, no standardized labeling requirements exist specific to this ingredient. That makes it essential to know exactly what to look for, and what to avoid, before buying.
Key Takeaways
- The Supplement Facts panel should list C15 (pentadecanoic acid) as its own line item in milligrams, not bundled into an unlabeled fatty acid blend.
- The one published human trial used 200 mg per day; [5] products well below or far above this range are outside what existing studies have assessed.
- Third-party testing certification or an independently issued COA is the most meaningful quality signal available in this largely unregulated supplement category.
- Claims that C15 is a proven ‘essential’ fatty acid or that it treats disease overstate current scientific consensus and regulatory status: treat such language as a red flag.
- Form (free fatty acid versus triglyceride-bound), source material, storage guidance, and transparent manufacturer contact information are all legitimate criteria for comparing products.
What Is in Fatty15? The Ingredients List
According to Fatty15, the capsule holds a single ingredient: pure pentadecanoic acid (C15:0), sold under the name FA15 [7].
- Active ingredient: pentadecanoic acid (C15:0), as a powder the company calls FA15 [7].
- What the company says is not in it: no preservatives, fillers, oil, dairy, gluten or artificial colors; described as vegan-friendly and lactose-free [7].
- Purity: the company says each batch is tested to at least 98% purity [7].
- Suggested use: the company recommends starting at 1 capsule a day [7].
These are the company’s own statements, not independent lab results. FDA’s inventory lists pentadecanoic acid only as a flavoring agent or adjuvant [9], so the label is the place to check the capsule material and the exact amount per capsule.
Start With the Supplement Facts Panel: What It Must Tell You
Every legal dietary supplement sold in the United States must include a Supplement Facts panel listing the serving size, servings per container, and amount per serving of each dietary ingredient. For a C15 product, the panel should clearly state the amount of pentadecanoic acid in milligrams per serving, not merely the total fat or the weight of the oil blend the C15 is extracted from.
This distinction matters. Some products list a ‘fatty acid complex’ or ‘C15-rich oil’ by weight, making it impossible to determine how much actual pentadecanoic acid you are consuming. A transparent label isolates C15 as its own line item. If you cannot determine the milligram dose of pentadecanoic acid specifically, treat that as a significant gap in label transparency.
Also check that the label specifies the source material. Fatty15 says its supplement is made by chemical synthesis rather than extracted from dairy or fish, though some other listings advertise milk-derived sources [7]. Odd-chain fatty acids are rare in nature and can be produced from renewable carbon sources by microbial fermentation, and Fatty15 describes its own ingredient as synthesized.[2] The source does not automatically determine quality, but an unlabeled or vague source should prompt further investigation (the section below on where the C15 comes from explains why it is worth asking).
Understanding Dose: What Published Research Has Used
The one published human trial used 200 mg of C15 per day for 12 weeks in 30 young adults and reported no significant adverse events; the trial was supported by the supplement maker [5]. However, because the research base is still limited and largely conducted or funded by Epitracker-affiliated researchers, there is not yet a formally established recommended daily intake backed by independent regulatory review.
The dose numbers you will see, and where each one comes from
The only trial of C15:0 on its own tested 200 mg a day; higher label doses rest on company safety statements.
Milk figure is a UK estimate for semi-skimmed milk. FDA's own record lists pentadecanoic acid only as a flavoring. Source: Sellem et al., British Journal of Nutrition 2022; Robinson et al., The Journal of Nutrition 2024; Nutritional Outlook 2026; Fatty15 FAQ 2026.
Data table
| Item | Value |
|---|---|
| One 200 ml glass of semi-skimmed milk | 20 mg |
| Daily dose in the only trial of C15:0 alone | 200 mg |
| GRAS food limit, as reported by trade press | 245 mg |
| Fatty15: safety studies completed up to | 250 mg |
Chart: c15hub.com: The dose numbers you will see, and where each one comes from
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Research note: FDA’s Substances Added to Food inventory (formerly EAFUS) lists pentadecanoic acid only as a flavoring agent or adjuvant [9].
Products that provide substantially less than 100 mg per serving may not deliver amounts comparable to those studied. Products marketing very high doses, above 500 mg or more, are moving well beyond what peer-reviewed research has examined, and higher is not automatically better or safer. When evaluating a label, compare the per-serving dose with the 200 mg a day used in the one small published human trial [5].
Pay attention to whether the product recommends one or multiple servings per day. A capsule listing 50 mg C15 per serving with a two-capsule daily dose delivers 100 mg total, which is within the studied range. Read serving size and daily serving instructions together before drawing conclusions about dosing adequacy.
Form Matters: Free Fatty Acid Versus Triglyceride-Bound C15
C15 supplements appear on the market in different forms. Some products deliver C15 as a free fatty acid (sometimes labeled FA-C15 or as purified pentadecanoic acid), while others provide it as part of a triglyceride structure within a fatty acid-rich oil. The distinction has potential relevance to absorption and bioavailability, though head-to-head comparative data in humans is limited.
One small study of 15 healthy adults found that blocking pancreatic lipase cut absorption of triglyceride-bound heptadecanoic acid by 71% but left absorption of free pentadecanoic acid unchanged [8].
Free fatty acid forms are typically associated with higher purity percentages because the C15 has been isolated from the surrounding lipid matrix. Triglyceride-bound forms may more closely resemble how C15 appears naturally in food, but the actual C15 content per gram of oil can vary considerably depending on the source material and extraction process.
A label should clearly indicate which form is present. If the label lists an oil blend or a fatty acid complex without specifying the form or the precise C15 content within that blend, you cannot confirm what you are purchasing. Seek out products where the form is stated and the C15 content is quantified as a distinct ingredient.
Where the C15 in a Capsule Comes From
Most fatty acids in nature have an even number of carbons because they are built two carbons at a time from acetyl-CoA. An odd-chain fatty acid has to start from a three-carbon unit, propionyl-CoA, so the practical problem in making C15 is getting enough propionyl-CoA inside the producing cell. A 2026 review in World Journal of Microbiology and Biotechnology describes how odd-chain fatty acids are made at scale: short ones such as propionic, valeric and heptanoic acid mostly by anaerobic fermentation in mixed microbial communities, and long ones, the category C15 belongs to, by single strains of yeast, bacteria or microalgae. It also frames the market as spanning food, chemical and biofuel uses, with supplements as one buyer among several.[2]
A 2025 study in Biomolecules shows what yield engineering looks like. Working with the oil-accumulating yeast Yarrowia lipolytica, researchers found that adding 0.5 percent 1-propanol to the growth medium raised C15 production to 76.68 mg/L, a 794.7 percent increase over the control, while total lipid stayed at 1.54 g/L, unchanged. The yeast made the same amount of fat with a much larger share of it as C15, because the propanol was oxidized and branched-chain amino acid degradation increased, expanding the propionyl-CoA pool.[3] That is a research-scale figure: at 76.68 mg/L, a 100 to 300 mg daily dose would correspond to roughly 1.3 to 3.9 litres of culture before any purification losses, which helps explain why odd-chain fatty acids are relatively expensive to produce.
Some products are not purified C15 at all but whole microalgal oils. A 2021 toxicology paper evaluated an odd-chain algal oil made up of pentadecanoic and heptadecanoic acids, which is a different product from purified C15 because it delivers C17:0 as well.[4] For label reading, the practical point is to look for a statement of whether the product is purified C15 or a mixed odd-chain oil, since most labels do not disclose it.
Purity and Third-Party Testing: The Most Important Quality Signal
Because dietary supplements in the United States are not required to undergo pre-market approval by the FDA, the burden of quality verification falls largely on manufacturers and third-party certifiers. A C15 label that carries a certificate of analysis (COA) from an independent laboratory (or a recognized third-party seal such as NSF International, USP, or Informed Sport) provides meaningful evidence that the product has been independently tested for identity, potency, and contaminants.
When evaluating a COA, look specifically for confirmation that the stated milligrams of C15 per serving match the tested content, that heavy metal levels (lead, cadmium, arsenic, mercury) are within acceptable limits, and that the product is free of microbial contamination. A COA provided only by the manufacturer’s in-house laboratory carries less weight than one issued by an accredited external facility.
Products that make no mention of third-party testing, display no certifications, and do not offer a COA upon request should be viewed with caution. In a market with limited regulatory oversight, third-party verification is one of the strongest proxies for product integrity available to consumers.
Red Flags: Label Language That Should Give You Pause
Several patterns on supplement labels warrant skepticism. Claims that a product ‘treats,’ ‘cures,’ ‘prevents,’ or ‘reverses’ any disease are prohibited for dietary supplements in the United States and indicate a company willing to misrepresent regulatory boundaries. Structure/function claims (such as ‘supports healthy aging’ or ‘promotes cellular health’) are permitted but must be accompanied by a disclaimer stating the FDA has not evaluated the claim.
Be cautious of labels that reference C15 as a ‘proven essential fatty acid.’ The hypothesis that C15 meets criteria for essentiality, meaning the body cannot synthesize adequate amounts on its own, has been proposed by Epitracker researchers but has not been formally recognized by the National Academies of Sciences, Engineering, and Medicine, nor adopted in official dietary reference intake frameworks. A label presenting this classification as established fact overstates the current scientific consensus.
Other red flags include: no listed amount of C15 per serving (only a proprietary blend total), no identifiable manufacturer address or contact information, exaggerated comparisons to pharmaceutical drugs, absence of a lot number or expiration date, and testimonials that describe dramatic disease reversal. These patterns, individually or in combination, suggest a product prioritizing marketing over accuracy.
Additional Label Elements Worth Checking
Beyond the core Supplement Facts panel, examine the ‘Other Ingredients’ section. Fillers, binders, and encapsulation materials are standard and generally benign, but individuals with specific allergens or sensitivities (soy, fish, shellfish, gluten) should verify these are absent or clearly disclosed. Gelatin capsules are not suitable for vegetarians or vegans; plant-based alternatives should be labeled as such.
Storage instructions matter for fatty acid stability. C15, like other fatty acids, can oxidize over time when exposed to heat, light, or air. Products that require refrigeration after opening, or that package the supplement in dark or opaque containers with an oxygen barrier, are demonstrating awareness of lipid stability. A product with no storage guidance at all, packaged in clear plastic, may have a shorter effective shelf life than the expiration date implies.
Finally, verify that the manufacturer lists a physical address and a means of contact. Reputable supplement companies stand behind their products and make it straightforward for consumers to request documentation, ask questions, or report adverse effects. Anonymous or contact-poor labeling is a structural red flag regardless of the ingredient in question.
A Worked Example: Reading a Single-Ingredient C15 Label
A single-ingredient product is the easiest case to read. According to Fatty15’s own product pages and FAQ, its capsule lists one ingredient, a pure C15 powder it calls FA15, at 100 mg per capsule, with no fillers, oil or preservatives, and the brand recommends starting at one capsule a day. These are manufacturer statements, not independently verified, and the brand’s own pages did not name the capsule shell material, so check the bottle if that matters to you. Because there is no filler, 100 mg of powder fills only about half the capsule, and the brand says apparent fill varies with how tightly the powder packs and with humidity. A nearly empty capsule is a reason to contact customer service, not automatically a sign of a counterfeit.
The gummy format shows why format changes the label. The brand’s gummy page lists the same 100 mg of C15 in 60 vegan gummies, with fructooligosaccharides, purified water and citrus pectin as the base, plus natural flavor, sunflower lecithin, organic acids, fruit and vegetable juice for color, coconut oil and carnauba wax as a coating, and rebaudioside M, a stevia extract. Anyone who prefers a short ingredient list has a practical reason to choose the capsule. Fatty15 says each batch is tested to confirm at least 98 percent purity; no certificate of analysis was published on the pages reviewed, so that remains a claim to request documentation for, using the COA checklist above.
What Published Safety Data Does and Does Not Cover
Labels and FAQs often lean on safety statements, so it helps to know what the peer-reviewed work actually covers. A 2024 randomized, double-blind trial gave 200 mg of C15 or placebo daily for 12 weeks to 30 young adults with overweight or obesity (20 on C15, 10 on placebo). Circulating C15 rose 1.88 μg/mL more than placebo (P = 0.003) and no significant adverse events occurred. The liver enzyme and hemoglobin changes the paper reports compare participants who ended above 5 μg/mL with those who did not, inside the treated group, so they are a signal for further study and not a placebo-controlled benefit.[5] A 2021 rat study of an odd-chain algal oil, fed at 5, 10 and 15 percent of the diet for 13 weeks, found no adverse effects and no mutagenicity or in vivo chromosome damage, but it tested an oil blend of C15 and C17, not a purified C15 capsule, so it supports general tolerability of odd-chain fatty acids and does not certify any one product.[4] A 2022 cell-based study reported that pure C15 was non-cytotoxic at all concentrations tested across 12 primary human cell systems, while EPA was cytotoxic in four at 50 μM; these are cell experiments by authors whose patents are licensed to a company that sells a C15 supplement.[6] Taken together, the evidence supports short-term tolerability at about 200 mg a day in a small group. It does not establish long-term safety, safety in pregnancy, or equivalence between brands.
The 2024 trial was supported by Seraphina Therapeutics, which supplied the capsules, and apart from a drop in the liver enzyme GGT it found no significant changes in any secondary outcome [5].
🛒 Where to Buy Pentadecanoic Acid (C15)
- Fatty15 (official site) 20% off with code SFKKDBQQ
capsules, 100 mg C15 per capsule; 1 capsule/day starter, 2 capsules/day maintenance: Category creator, from the original Epitracker research team (Venn-Watson et al.); uses a patented, sustainably-sourced pure C15 ingredient; most expensive per-capsule but reference product for all comparisons - Double Wood Supplements Pentadecanoic Acid C15
capsules, 200 mg C15 per serving (2 capsules): Generic C15 supplement; significantly lower price than Fatty15; no independent clinical trials on this specific product; good option for budget-conscious buyers who want to trial the fatty acid - Sports Research Pentadecanoic Acid C15
softgels, 100 mg C15 per softgel: Established supplement brand with strong Amazon presence; softgel form may aid fat-soluble absorption; competitively priced mid-tier option - BulkSupplements Pentadecanoic Acid Powder (C15)
powder, 100 to 300 mg per measured serving: Most economical option for higher-dose protocols or stackers; requires a milligram-accurate scale; no excipients or additives; not recommended for beginners unfamiliar with powder dosing
As an Amazon Associate we earn from qualifying purchases. C15 products vary widely in how much pentadecanoic acid they actually contain, so check that the Supplement Facts panel lists C15 in milligrams as its own line item rather than bundling it into a fatty acid blend, and compare the per-serving dose with the 200 mg a day used in the one small published human trial [5].
A Note on the Evidence
C15 research is preliminary, largely conducted by a small group of researchers with financial ties to Epitracker, and has not been independently confirmed in large randomized trials; no regulatory body has evaluated C15 for any health claim or established a recommended intake. If you are pregnant, breastfeeding, taking medications, or managing a health condition, consult a qualified healthcare provider before adding any C15 supplement to your routine.
Frequently Asked Questions
What is the difference between C15 and other fatty acid supplements?
C15 is a saturated odd-chain fatty acid, structurally distinct from even-chain saturated fats like palmitic acid (C16:0) and from unsaturated fatty acids like EPA or DHA. Epitracker researchers propose it may interact with cellular membranes and metabolic receptors in ways that differ from common dietary fatty acids, though this research is early-stage and has not been independently replicated at scale.
Is there a daily value percentage listed for C15 on supplement labels?
No. Because no established Daily Value for C15 exists in U.S. regulatory frameworks, labels are not required to, and typically cannot, list a percent daily value for this ingredient. This is expected and not itself a red flag, but it does underscore that no regulatory body has set an official recommended intake.
How do I verify that a product actually contains the C15 amount listed?
Request a certificate of analysis from the manufacturer issued by an accredited third-party laboratory. The COA should show tested C15 content per serving and confirm it matches the label claim within an acceptable variance range, typically plus or minus ten percent. If a company cannot or will not provide this documentation, that is a significant transparency concern.
Are C15 supplements safe?
The one published human trial (200 mg per day, 12 weeks) reported no significant adverse events [5]. However, the available research base is limited in size and largely connected to the researchers who advanced the C15 hypothesis. As with any supplement, individuals who are pregnant, breastfeeding, taking prescription medications, or managing chronic conditions should consult a healthcare provider before use.
Does label transparency differ between free fatty acid and oil-based C15 products?
It can. Free fatty acid forms tend to make it easier to list an exact milligram quantity of C15 because the compound has been isolated. Oil-based products vary more widely; some clearly quantify the C15 content within the oil, while others list only the total oil weight, leaving actual C15 dose unknown. Prefer products that specify C15 milligrams regardless of form.
What does 'proprietary blend' on a C15 label mean, and should I be concerned?
A proprietary blend groups multiple ingredients under a single total weight without disclosing individual amounts. For a single-ingredient C15 product, there is no legitimate reason to use this structure: it exists to obscure dosing. For combination products containing C15 alongside other ingredients, a proprietary blend prevents you from confirming how much C15 is actually present. Treat its use as a reason to seek a more transparent alternative.
References
- Venn-Watson S, Lumpkin R, Dennis EA. Efficacy of dietary odd-chain saturated fatty acid pentadecanoic acid parallels broad associated health benefits in humans: could it be essential? Scientific reports. 2020;10(1):8161. PMID 32424181
- Timmers RA, de Vicente M, Rosa-Masegosa A, et al. Recent advances in microbial production of odd-chain fatty acids. World Journal of Microbiology and Biotechnology. 2026;42(1):40. PMID 41528657
- Cong J, Hu X, Lu D, et al. Multi-omics analysis reveals 1-propanol-induced pentadecanoic acid biosynthesis in Yarrowia lipolytica. Biomolecules. 2025;15(11):1618. PMID 41301536
- Matulka RA, Howell LA, Chennupati BP, Bock JT. Safety evaluation of odd-chain fatty acid algal oil. Food and Chemical Toxicology. 2021;156:112444. PMID 34332011
- Robinson MK, Lee E, Ugalde-Nicalo PA, et al. Pentadecanoic acid supplementation in young adults with overweight and obesity: a randomized controlled trial. The Journal of Nutrition. 2024;154(9):2763-2771. PMID 39069269
- Venn-Watson SK, Butterworth CN. Broader and safer clinically-relevant activities of pentadecanoic acid compared to omega-3: evaluation of an emerging essential fatty acid across twelve primary human cell-based disease systems. PLoS One. 2022;17(5):e0268778. PMID 35617322
- Fatty15 (Seraphina Therapeutics) Fatty15 FAQs. Fatty15 (Seraphina Therapeutics) (2026). source
- Stallings VA et al. Diagnosing malabsorption with systemic lipid profiling: pharmacokinetics of pentadecanoic acid and triheptadecanoic acid following oral administration in healthy subjects and subjects with cystic fibrosis. International journal of clinical pharmacology and therapeutics (2013). PMID 23357842
- U.S. Food and Drug Administration Substances Added to Food: pentadecanoic acid. U.S. Food and Drug Administration (2026). source
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. Content is for informational purposes only and is not medical advice; consult a qualified healthcare provider before starting any supplement. As an Amazon Associate we earn from qualifying purchases.