C15:0 Makes The Good Fat List: Heart & Cholesterol Health

September 13, 2026

Welcome to Issue 187 of Science Says! Our weekly newsletter where you’ll learn the latest healthy aging and C15:0 research news that our team of doctors, scientists, and experts are most excited about—without having to go search for it.

Eric and Steph
Co-Founders, Doctors, Nerds

What Dr. Stephanie Venn-Watson, our co-founder and author of The Longevity Nutrient and over 80 peer-reviewed scientific publications, is reading.

Healthy Aging

C15:0 is on the right side of nutritional fat math

Seed oils, dairy fat, eggs? Determining which foods are “good” or “bad” for us continues to be confusing. This is due in part to, well, the parts that are in foods. The upside is that nutritional science is increasingly studying differences among specific ingredients in foods – which is helping us understand that some molecules in foods can be harmful, while others are helpful (aka, they are true nutrients). A just-released review in The Journal of the Academy of Nutrition and Dietetics Global Reports proposes two new mathematical equations that take both good and bad fatty acids into account. By doing so, not only can the nutritional quality of our current foods be assessed, these indices can be leveraged with technology to make our foods healthier. Let’s dive in.

So, how was math used to calculate good vs. bad fats?

In their review, Machate et al. introduce two new equations to score the nutritional quality of fat sources as they relate to our heart health. The first is called the atherothombogenicity index (aka, the ATI). Based on their summary of the current literature focusing on specific fatty acid groups, Machate et al. propose the following to calculate how risky a mixed-fat food source is to our cardiovascular health:

Source: Machete et al. JAND Global Reports (2026)

Translated, this equation says that the sum of the following fatty acids in the numerator are BAD for our cardiovascular health:

LCFAs: Long chain fatty acids, defined as C14:0, C16:0 and C18:0
ɷ-6 PUFAs: omega-6 polyunsaturated fatty acids
Trans-FAs: trans-fatty acids

While the sum of the following fatty acids in the denominator are GOOD for our cardiovascular health:

MCFAs: medium-chain fatty acids, defined as C6:0 to C12:0
OCFAs: odd-chain saturated fatty acids, defined as C13:0, C15:0 and C17:0
VLCSFAs: very long-chain saturated fatty acids, defined as C20:0 to C38:0
MUFAs: monounsaturated fatty acids
ɷ-3 PUFAs: omega-3 polyunsaturated fatty acids
ɷ-3:ɷ-6 PUFAs: omega-3 to omega-6 polyunsaturated fatty acid ratio

In summary, foods that have more of the top fats and less of the bottom fats are not-so-good for our cardiovascular health.

Got it. So, what is the second equation?

The second equation is called the hypocholesterolemic/hypercholesterolemic (H/H) ratio. As explained by Machate et al., this ratio uses the existing literature on specific fatty acid groups as they relate to lower versus higher cholesterol levels. It is also the inverse of the ATI.

Source: Machete et al. JAND Global Reports (2026)

In summary, foods that have more of the top fats and less of the bottom fats are better for our cholesterol health.

How this all adds up.

While these equations may appear complicated, they get across a simple message: Foods contain a mix of different fats. Some are net-good. Some are net-bad. And the more we can get of the good fats…and less of the bad fats…the better our cardiovascular health.

While we’ve known this for a while, advancements in nutritional science are helping to evolve this basic knowledge – including adding odd-chain saturated fatty acids (aka, C15:0) to the good side of this story.

Better yet, Machate et al. introduce a number of ways that good fatty acids can be increased and bad fatty acids can be decreased, resulting in nutritional food sources that can better support our heart health. Go, science.

The New Fatty Acid Kids on the Healthy Nutrient Block: Odd-Chain Saturated Fatty Acids (including you, C15:0)

If you’re reading Science Says!, the addition of odd-chain saturated fatty acids (OCFAs) to these good-for-your-heart-health equations isn’t surprising.

While Machate et al. defined OCFAs as C13:0, C15:0 and C17:0, they primarily pointed to literature focusing on the health benefits of C15:0 and C17:0. Taking this one step further, numerous studies support C15:0 as the goldilocks OCFA for our long-term health. Here are just a few examples why:

When comparing C15:0 and C17:0, C15:0 supplementation was better at supporting healthy cholesterol, healthy glucose, and lower proinflammatory cytokines across multiple preclinical studies.
Only C15:0 – and not C17:0 – was an essential nutrient in a C. elegans model for neurodevelopment. Absent any other nutrient (including carbohydrates, proteins, or other lipids), C15:0 alone restored normal neurodevelopmental growth.
Studies support that our body cannot make enough C15:0 on its own to meet what is emerging as a critical threshold for supporting our basic physiological health. This means we require certain amounts of dietary C15:0 to maintain and optimize healthy circulating C15:0 levels. In contrast, our bodies use C15:0 to make C17:0.

For these reasons and more, C15:0 has gained the most attention as a healthy OCFA to support our long-term health – including Machate et al.’s inclusion of C15:0 in supporting cardiovascular health. Thanks for nerding out on some good-for-you math, and have a great week, everyone!