A New Supplement Behind the Blue Zone Secret: Meet C15

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Isla Hart

October 21, 2025

You’ve probably heard of the “Blue Zones”—those special regions on Earth where people regularly live to 100 and beyond, and not just live, but thrive—remaining vibrant, active, and full of life well into old age. Scientists around the world are trying to uncover the secret to this phenomenon. One recent theory points to a common factor in the diets of these centenarians: an adequate intake of C15 fatty acid, an essential fatty acid found in every cell of our bodies.

We got this information straight from the source—Stephanie Venn‑Watson, the researcher who discovered this fatty acid. She’s a public health scientist with 40 patents and over 70 peer-reviewed publications, and also a veterinary epidemiologist. We now have a new tool in our longevity arsenal, thanks to her work with aging dolphins in the U.S. Navy. But more on that later.

What is C15, and how is it Different from Omega-3?

There are essential amino acids and fatty acids—proteins and fats that our bodies cannot produce on their own, but are vital for survival. Omega-6 and omega-3 are among these essential fats and must be obtained from food. Typically, modern diets have an overabundance of omega-6, found in grains and vegetable oils, while we’re often deficient in omega-3, mainly found in wild—not farmed—fatty fish.

С15 Fatty Acid Supplement — *C15 activates receptors responsible for metabolism, immunity, mood, sleep, and appetite*

Cheese and other dairy are C15 sources — *Include butter, cheese, lamb, and fish for your C15 boost*

*Fish is an excellent source of both C15 and omega-3*

For nearly 100 years, since their discovery in 1929, it was believed that the topic of essential fatty acids was complete. That changed in 2020 when Stephanie discovered C15:0 (pentadecanoic acid) and its critical role in health and longevity. Although the body can produce C15, it often doesn’t make enough, so dietary sources of C15 fatty acid are crucial.

What is C15 Good For?

Ongoing research suggests C15 may:

Support metabolic health and help regulate cholesterol levels, which is vital for heart and vascular health.
Offer neuroprotective benefits, potentially aiding brain health and function.
Serve as a longevity marker—animals (and potentially humans) with higher C15 levels tend to live longer.

Like omega-3, C15 plays a role in forming and maintaining cell membranes, making it essential to every cell in the body. However, unlike polyunsaturated omega-3s, C15 is a saturated fatty acid, which makes it more stable and possibly better at protecting cells from aging.

How to Know if You’re Deficient in C15

Symptoms of C15 deficiency are non-specific — think poor sleep and chronic fatigue. But it’s hard to tell whether that’s due to a lack of fatty acids or just too many deadlines.

Today, it’s possible to get a blood test for C15 levels. MDPI

Infants receive C15 through breast milk. Those who were formula-fed or had a short breastfeeding period may have had a deficiency from infancy. If the mother was low in C15 herself, even breast milk might not have been sufficient. Modern diets also typically lack this nutrient. ScienceDirect

The easiest way to spot a deficiency? In hindsight. Start eating more C15-rich foods or take a supplement, and if you notice significant improvements, chances are you had (or still have) a deficiency.

What Foods Contain C15—and What’s With the Dolphins?

Stephanie Venn-Watson worked with retired dolphins from the U.S. Navy Marine Mammal Program. These large, intelligent mammals share aging mechanisms similar to humans. She compared blood samples from two groups—one living in California, the other in Florida—and found that Florida dolphins were healthier and stronger, thanks to their C15‐rich fish diet.

C15 is found in fish like surubim catfish, pescando, trahira, and tucunaré. Have you ever heard of them? Neither had we. Apparently, they’re dolphin delicacies. Fortunately, dairy products are more accessible sources—especially those from pasture-raised animals, ideally sheep or goats in mountainous regions.

In Sardinia, one of the world’s Blue Zones, locals consume a lot of pecorino cheese—and live to 100. For the rest of us, supplements may be the best option, with cheese as a tasty bonus.

Can C15 Replace Omega-3 Fatty Acids?

Both omega-3 and omega-6 are essential fatty acids—our bodies can’t make them, and we must get them from food. Even omega-6, despite its pro-inflammatory reputation, is vital, since inflammation is part of the body’s defence system. The key lies in balance.

C15, on the other hand, is “conditionally essential”—our body can make it, but not always in sufficient quantities. It’s not a substitute for omega-3 or omega-6, but a complement. We know that when omega-6 dominates over omega-3 in cell membranes, cell function suffers. The same goes for C15—it’s a missing piece in the health puzzle, not a replacement.

Are There Any Side Effects or Risks?

C15 is considered safe in the research so far. The main issue is that it’s relatively new to science, and much of the existing research was conducted in partnership with Stephanie Venn-Watson’s company.

As for natural sources, fatty dairy has pros and cons. Some contain lactose, which isn’t ideal for everyone—even without lactose intolerance. Casein, a primary milk protein, can also cause issues for some. Butter, however, is a pretty safe bet.

Good quality butter not only has C15 but also contains vitamins A, D, E, and K2; butyrate, which supports gut health; and conjugated linoleic acid (CLA), which—miraculously—helps with weight loss.

Weight loss, health, longevity, and a buttery taste—what could be better?