C15:0’s Essentiality Is Put To An Old School Test - And Gets An “A”

Healthy Aging

C15:0 Essentiality Is Re(re)validated

Exciting news to share, nerdy do-gooders. You may recall that, a few weeks back, we covered a paper by Ciesielski et al., where they independently reviewed whether C15:0 met the rare criteria of an essential fatty acid. They concluded, similar to our studies from 2020, that C15:0 is indeed essential. Which is great.

Now, a pivotal study just published by Ciesielski et al. in The Journal of Nutritional Biochemistry put C15:0 to the old-school test for essentiality – the same one used to discover and confirm vitamins and other essential fatty acids a hundred years ago. So, let’s dive in to understand how C15:0 passed another test of essentiality.

Remind me again. What is an “essential fatty acid”?

Ah, a good place to start. An essential fatty acid is a nutrient that our bodies must have to maintain our baseline physiological health. Since our bodies don’t make enough of these essential fats, we must get adequate amounts routinely from our diet or supplements.

There are three known essential fatty acids:

• Linoleic acid (LA, an omega-6 fatty acid)
• Alpha-linolenic acid (ALA, an omega-3 fatty acid)
• C15:0 (pentadecanoic acid, an odd-chain saturated fatty acid)

Three independent teams (Venn-Watson et al., Dornan et al., and Ciesielski et al.) have all concluded that C15:0 meets the criteria of being an essential fatty acid.

So, what was this latest old-school study about?

All vitamins and essential fatty acids we know today were identified during a big discovery boom between 1913 and 1948 (except C15:0, of course, which was published in Scientific Reports in 2020).

Many of these essential nutrients, including LA and ALA discovered by Dr. George and Mildred Burr, were confirmed using the following general rodent study approach:

• Give female rodents a diet deficient in the essential nutrient, including before, during and after pregnancy (including lactation).
• Assess the baby rodents for signs of nutritional deficiencies, including while on a deficient diet as young rodents.
• Supplement the young, deficient rodents with the essential nutrient, and monitor for signs of reversed nutritional deficiency.

As such, Ciesielski et al. repeated this study design, which included retesting LA (the first discovered essential fatty acid) and C15:0 (the latest discovered essential fatty acid). Here’s what they found.

Finding #1: Momma rodents lacking dietary C15:0 had no C15:0 in their milk.

While the healthy control female rats fed an essential fatty acid diet had 4% C15:0 (of total fatty acids) in their milk for their pups, those on the deficient diet had no C15:0 in their milk. Which means that moms required dietary C15:0 to have C15:0 in their milk… and without it, their pups were born into a C15:0-deficient world.

Finding #2: Pups lacking C15:0 had poorer growth.

Consistent with that found in human studies, C15:0-deficient pup rats had significantly poorer growth compared to healthy controls. At 3 weeks of age, the deficient pups had a 23% lower body weight compared to non-deficient pups.

Finding #3: Deficient pups supplemented with C15:0 had increased body growth rates.

During the most critical growth period, restoring C15:0 into the deficient pups’ diets resulted in a significant increase in their growth rate compared to non-C15:0 supplemented pups. Importantly, C15:0 was just as good at restoring good growth as LA (the other essential fatty acid tested).

Further confirmation that C15:0 is essential.

The original study that helped to confirm linoleic acid as an essential fatty acid back in 1929 was successfully repeated in this 2024 study. Importantly, C15:0 was confirmed to be as essential as linoleic acid using the same study methods.

Based on their findings, the authors conclude the following:

“C15:0 supplementation had a positive effect on growth in response to essential fatty acid deficiency in rats. This effect on growth was observed during the juvenile period in rats… which in human life would correspond to… 6 months to 11.5 years of age.

In humans, this development period of the first 1,000 days is critical… in which adequate nutritional intakes are vital to enhance children’s growth and health.

Since C15:0 can positively affect the growth during this early period of life and because it is a specific fatty acid of milk, C15:0 could be a direct… actor in early development.”