Pentadecanoic Acid and the Full-Fat Paradox
Around 40 years ago, doctor-types started telling people to cut down on their intake of saturated fats so that their cholesterol and subsequent risk of heart disease would dwindle down.
People listened. In the 20 or so years that followed, average whole milk consumption per person dropped from around 283 grams (a little more than a cup) to 65 grams per day, a more-than four-fold reduction.
You can credit this recommendation with nearly eradicating obesity, type 2 diabetes, metabolic syndrome, and non-alcoholic fatty liver disease.
What's that? That didn't happen? All those things got worse despite the decrease in whole milk consumption?
Now it might just be a case of "correlation fallacy" where the decrease in whole milk consumption had nothing to do with the rising incidence of those diseases. But maybe not. A study involving 25,000 children that spanned 18 years gave a surprising clue: Kiddies who drank whole milk had a lower risk of obesity compared to children who drank down the watery brews that are non-fat or 1%-fat milk.
But there's more. Several other studies have found associations between full-fat dairy intake and reduced incidence of several diseases. Could pentadecanoic acid be responsible?
Whole milk contains a whole bunch of saturated fatty acids, the vast majority of which are termed "even-chained." Examples include myristic acid (C14:0), palmitic acid (C16:0), and stearic acid (C18:0). See how all those fatty acids have an even number of carbon atoms?
However, whole milk also contains "odd-chain" saturated fats. One of these is known as pentadecanoic acid and, as the Latin name suggests (the Greek prefixes for 5 and 10), it has 15 carbon atoms (C15:0), an odd number.
It's starting to increasingly look like having high blood levels of this odd-duck fatty acid plays a big part in health and mortality, so much so that many scientists now consider it to be an essential fatty acid, essential as in you gotta' have it. Essential like Spock was to Kirk; essential like dental floss is to a dental hygienist; or essential like butter is to a bowl of good popcorn, which, incidentally, because of these findings, might actually be a terrifically healthy snack.
It seems butter, like whole milk and other full-fat dairy products, also contains pentadecanoic acid, and popcorn itself is chockfull of polyphenols, much more than many fruits and vegetables. Combine the two, as the movie theater gods ordained it, and you just might have a healthy, possibly life-extending snack.
But leave the Orville Redenbacher in the cupboard and the Land O'Lakes in the fridge for now. You need some supportive evidence before you spring this great news on your skeptical friends or family.
Here's the deal: Those even-chain fatty acids (ECFAs) I listed above? They've all been implicated in increased risk of inflammation, heart disease, and Type 2 diabetes in humans.
Contrast that with high dietary intake of odd-chain fatty acids (OCFAs). They seem to offset the possible metabolic damage caused by the ECFAs as they've been associated with lower risks of chronic inflammation, cardiovascular disease, metabolic syndrome, obesity, type 2 diabetes, chronic obstructive pulmonary disease (COPD), non-alcoholic fatty liver, pancreatic cancer, and other conditions.
One hefty study followed 14,000 people for 14 years and found that increased dietary intake of OFCAs was associated with lower mortality rates in both men and women, while higher ECFA intake was associated with higher mortality, at least in women.
Another observational study, this one involving dolphins, found that the marine mammals responded to higher intake of OFCAs much the same as humans – they had lower risk of metabolic syndrome and liver disease. Of course, the dolphins didn't get additional OFCAs by eating full-fat dairy products. Instead, they got them through eating certain types of fatty fish. More on that later.
A lot of other studies have also examined specific, individual effects of OFCAs in humans or human cell lines. One found that they were partial agonists of all three PPAR isoforms. PPARs are located throughout the body, and they regulate inflammation and metabolism by responding to dietary fats. Since OFCAs are partial agonists, they give the PPARs a helping hand and make them more efficient in their noble biochemical actions.
Another found that OFCAs repaired mitochondrial function. One found that they lowered glucose and cholesterol (at least in mice). Still another study, this one using rabbits, found that they attenuated anemia, inflammation, and liver iron overload.
Furthermore, and perhaps most importantly, none found that the fatty acid was toxic to nearly any type of human cell they could throw at it. Neither did it have any "off-target" pharmacological activities (like growing a second, tiny head, or affecting any downstream chemical reactions in general).
Is pentadecanoic acid truly essential to human health? Does it deserve to join the ranks of EPA and DHA and other essential fatty acids? Let's look at the criteria that determine a fatty acid's essentialness:
- Is it required to maintain a healthy physiological state?
- Does the body make enough on its own?
- Does it require dietary intake to maintain healthy concentrations in the body?
It appears the answers are yes, no, and yes. As such, it deserves a membership card to the essential fatty acid club.
The problem with recommending additional intake of pentadecanoic acid is that its science is still in its infancy, and no one knows the "correct" amount to take.
We can, however, incorporate additional full-fat dairy products into our diet. That would include modest (at least until we know more) amounts of full-fat milk, full-fat yogurt, and even butter on our vegetables or on our popcorn.
There are, however, other foods that contain appreciable amounts of pentadecanoic acid. Among these are certain marine and freshwater fish. Unfortunately, the highest amounts are found in the hard-to-find or never-heard-of-by-normal-people fish of the mullet family: keeled mullet, golden grey mullet, flathead mullet, leaping mullet, and the least attractive of all the mullets, the thinlip mullet.
Don't fret, though, the old healthy-eating standbys, salmon and tuna, also contain decent amounts. Some non-fish foods also include measurable amounts of pentadecanoic acid, too, including chicken, cabbage, cucumber, and some seaweeds.
There are also some C:15 supplements available, but I think their manufacturers are jumping the fatty-acid gun a bit since the correct or optimal dosage is still unknown.
For the time being, I'd consider re-introducing a bit of full-fat dairy back into my diet; maybe mix my protein drinks with some whole milk a few times a week and, since Hunt for Red October is on tonight, think about adding some butter to my home-made popcorn.
- Dornan K et al. Odd chain fatty acids and odd chain phenolic lipids (alkyresorcinols) are essential for diet. J Am Chem Soc. 2021 Aug;98(8):813-824.
- Ozogul Y et al. Fat content and fatty acid compositions of 34 marine water fish species from the Mediterranean Sea. Int J Food Sci Nutr. 2009 Sep;60(6):464-75. PubMed.
- Venn-Wilson S et al. Efficacy of dietary odd-chain saturated fatty acid pentadecanoic acid parallels broad associated health benefits in humans: could it be essential? Sci Rep. 2020 May 18;10(1):8161. PubMed.