Is This Saturated Fat Really an Essential Nutrient? 15 Fast Facts About C15

This saturated fat is an essential nutrient. Or is it just media and supplement hype? I've been getting a lot, I mean a lot of requests to do a video on C15 fatty acid. And honestly, I'm caving into it because this is a really cool topic. And in this video, I want to run through 15 facts about C15. We will talk about insulin resistance, fatty liver, childhood obesity, dolphins, healthy aging, the best natural dietary sources of C15, and how changes in the food supply change C15 levels, and much more. And by the end of this video, hopefully, you'll have an implicit answer to that key question: is this sexy new fat, C15, legit? Alright, let's get started. 1. What is C15? I wanted to define it out of the gate and get the most boring fact out of the way. C15 is an odd-chain saturated fat. A saturated fatty acid is one without any double bonds, and when we are naming fats, the C represents the number of carbons, usually then followed by another number representing the number of double bonds. So by way of another example, C18:1 means 18 carbons and 1 double bond. This is the monounsaturated fat oleic acid, as in olive oil. And C15, or properly C15:0, is the topic of this discussion. 15 carbons, an odd number, and zero double bonds. Okay, boring aside, moving on. Two, C15 does appear to be an essential fat. C15 is very likely an essential fatty acid nutrient because our bodies can't make appreciable amounts of C15, and lack of dietary C15 can contribute to poor health outcomes. Indeed, there's relatively strong evidence for A, C15 is not readily made endogenously by the body. And it's not really made by appreciable amounts by the microbiome for that matter either. So we don't make our own C15. B, lower levels of C15 intake from the diet and also lower blood concentrations are each associated with poor health outcomes and actually higher mortality. And C, C15 supplementation in preclinical and some clinical studies which we will touch upon have been shown to be Well, C15 has been shown to be a bioactive signaling lipid, and the effects of C15 supplementation parallel the associative benefits seen in larger-scale human population trials. All this is to say, there's a good case to be made that C15 is actually an essential fatty acid. Alright, moving on, 3. Let's talk about population C15 deficiency. So building off the idea that C15 is an essential fatty acid, there should be evidence for C15 deficiency in populations. There is, of course, as I alluded to, and the culprit for a population's C15 deficiency is likely misguided dietary recommendations. Dietary guidelines tend to recommend reductions in saturated fat intake, lumping all saturated fat together as a conglomerate, and lumped into the bucket of saturated fat-rich foods is whole fat dairy. So there's recommendations to reduce whole fat dairy intake. Which is a major source of C15. In fact, in the decades following the recommendation by dietary guidelines to reduce saturated fat intake, whole fat milk intake has plummeted fourfold. I think that was a big mistake. Multiple studies have demonstrated associations between higher dietary intake of full-fat dairy and reduced risks of type 2 diabetes, cardiovascular disease, or childhood obesity. This reality that high-fat dairy can be very healthy is becoming more and more mainstream. And whether C15 is actually mediating the presumed protective health effects of full-fat dairy, or put another way, whether a C15 deficiency might be contributing to increased risks of chronic diseases like diabetes and cardiovascular disease, of course, remains to be rigorously proven. But before we get into the nitty-gritty and speak about specific studies, I want to take a tangent and dive into how C15 came into the limelight. So number 4, thank you dolphins. This discussion around C15 has really been promoted by Stephanie Van Watson. I hope I'm pronouncing her name correctly. I've never met her. She's a veterinary epidemiologist who was turned on to C15 as a topic by her study of Navy dolphins. Her research centered on how to help dolphins age better and healthier. And she and her colleagues discovered, to their surprise, that differences in C15 levels in dolphins were the major differentiator between healthy aging dolphins and unhealthy aging dolphins. Where dolphins were low in C15, they exhibited higher rates of metabolic syndrome, fatty liver, even hallmarks of Alzheimer's disease, and they overall had worse aging and earlier death. One thing led to another, and they found that there were many parallels with humans, where C15 deficiencies appeared to be linked with a host of similar age-related chronic diseases. Isn't that cool? Thank you, dolphins. And we'll have more to say about dolphins at the end if you stick around. Moving on, number 5: C15 and insulin resistance. Interestingly, lower circulating levels of C15— lower C15 concentrations are associated with the development of insulin resistance and type 2 diabetes. So for example, in one meta-analysis including 33 studies and over 100,000 adults, there was an inverse association between odd-chain saturated fats, including C15, and type 2 diabetes. And this has been verified by other studies. In another meta-analysis of prospective trials, even after adjustments for BMI and waist circumference, higher C15 levels were associated with a 20% reduced risk of developing type 2 diabetes later on, which is actually pretty stunning. Okay, moving on. Number 6: C15 and fatty liver in children. There appears to be an inverse association between dairy fat intake and C15 levels versus fatty liver in children. In other words, more dairy fat intake associated with less liver fat in children, and higher measured C15 levels likewise associated with less liver fat in kids. So to this I say, to schools directly, Kick out the approved low-fat sugary chocolate milk and bring back whole milk, please. All right, moving on. Number 7: C15 and longevity. Now, the data on C15 and longevity are, in my opinion, a bit weaker but still interesting. Food for thought. For example, in one study conducted in Sardinia, researchers assessed the plasma profiles of octogenarians in high longevity Eastern Mountain area in Sardinia and lower longevity Northern Sardinia and found that C15 levels were trending higher in the high longevity area. Now, I'd take these data in isolation with a grain of salt, or even a whole salt shaker, given that the study was small and probably underpowered. But when you frame these data with the data on dolphins and other animal data and other population data on healthspan and lifespan and C15, well, I'm left at the very least scratching my chin. And that's a pretty good thing when it comes to longevity literature. Okay, moving on. 8. C15 levels in the body decrease with age. All I have to say about this, because it's a fact, is tell Granny to eat her pecorino and mullet. And we'll get to that more in a moment. Okay, number 9: C15 and human randomized controlled trials on fatty liver. There have been very few human RCTs on C15. And that's not bad per se, it's just the state of the literature to date. But I did want to give a nod to one in which young adults with obesity with a mean BMI of 33.4 kg/m² were given C15 in double-blind controlled trial. And I won't say the results were groundbreaking, but they were interesting. Specifically, in those adults who achieved a threshold level of C15 as a result of supplementation, the threshold level being above 5 micrograms per milliliter, there did appear to be a significant improvement in some liver damage markers, the liver transaminases AST and ALT. And that's something. That said, I think one drawback of this intervention was the duration. It was only 12 weeks. And if I were designing this trial in an ideal world, I would've wanted longer period to see if positive effect emerged in the coming months. Nevertheless, credit where it's due, these studies are getting done and I'm sure we'll learn a lot more as the data develop, including about what optimal circulating and membrane levels of C15 should be. I've seen various ranges tossed about, like 0.16% to 0.64% circulating, but I'd really love more data on what is optimal, what is the goal for measuring it. But moving on, number 10: C15 and cellular fragility. So the connection between C15 and metabolic diseases is interesting, but of course you should now be asking, how? How does C15 promote good metabolic health? And one model has to do with cellular stability, specifically membrane stability. So cell membranes are made of fatty acids, and the composition of the membranes determines their properties. Including the fragility of the membrane and propensity to undergo a form of fat oxidation called peroxidation. I'll try to keep this pretty high level because I know it can get technical. But briefly, this is the model: deficiencies in C15 in cell membranes, levels below 0.2% of total fatty acids, might make cells, particularly red blood cells, susceptible to this form of oxidation, peroxidation. And fragile and damaged red blood cells can then be eaten up by immune cells, including resident macrophages immune cells in the liver. And the metabolic fallout of all of this includes more oxidation, peroxidation, programmed cell death, ferroptosis, and inflammation, which can be detected as increases in inflammatory markers and liver enzymes, like those we mentioned earlier, all on the path to liver disease. And impaired liver function leads to insulin resistance and increased risks of metabolic syndrome, diabetes, and cardiovascular disease. And for more on that, if you really do want the technicals of the cellular fragility model, I'll link to a paper below. All right, moving on. Number 11, a moment you've been waiting for, highest dietary C15 sources. So in terms of natural sources of C15, in the Western world, it's full-fat dairy. In fact, C15 is a relatively good biomarker for dairy intake, with higher intake of fatty dairy associated with higher C15 levels. And higher full-fat dairy intake and higher C15 levels each are associated with better health outcomes. But even among dairy, there is a hierarchy. And perhaps at the top of the list, the winner, pecorino cheese, a hard sheep's cheese that's one of my favorites. It's particularly rich in C15. In fact, to get the recommended, recommended in quotes, 200mg of C15 per day, you just need half an ounce, about 14 grams of pecorino per day. That's nothing. And to be honest, I generally eat pecorino by the like 100 or 150 gram serving, so I'm definitely getting my C15. And you can also get C15 from seafood, with some amazing sources being mullet, catfish, and sea bass. Okay, moving on. Number 12: changes in cow feed actually change C15 in their dairy. So the ways in which cows are fed, grass versus corn, affects the C15 in their milk. Specifically, there's a direct positive association between percent of grass fed to cows versus the C15 content in their milk, with 0% grass fed versus 30% grass fed versus 100% grass fed containing 0.77, 0.99, and 1.3% C15 respectively. This translates into a nearly twofold difference in the dietary C15 intake, even from whole fat milk, depending on whether or not the cows are fed grass. Or corn. Pretty cool. Okay, moving on. 13. C15 and the endocannabinoid system. This one really came out of left field for me, I think it's super cool. But to put it concisely, a C15 direct metabolite called pentadecanoic carnitine, which is basically just C15 bound to a carnitine molecule, is a full-acting agonist, or activator, of the endocannabinoid receptors CB1 and CB2. And it's actually this metabolite of C15 that really pops out among dolphins on high C15 diets around 6 months after supplementation. And in human cell studies, pentadecanoyle carnitine also appears to lower markers of inflammation like IL-1α and MCP-1. The human clinical effects remain to be determined, but there's actually potential for therapeutic benefits on inflammation, pain, mood, and sleep of this C15 carnitine-bound metabolite. Pretty cool, I think. Moving on, 14. C15 does not replace omega-3 fatty acids. Now, there's been a lot of talk about omega-3 versus C15, and I want to cut to the chase. I really don't think you can replace omega-3s with C15, and I don't want to recreate the wheel on this. My friend Nick V on the Physiotix channel did a great breakdown, so rather than recreate the wheel, I'll just link to that video below, and I encourage you to check it out. Nick does really nuanced breakdowns, and I appreciated learning from him on C15. Finally, dolphin cheese. For your final fact, have you ever wondered what dolphin milk and dolphin cheese taste like? Well, you can actually get some for just $13. I'm just kidding. This is actually just a funny beer cozy. I did look up if I could get dolphin cheese. Turns out you can't. But I suppose you can milk a dolphin, so you could theoretically make dolphin cheese. And while I do love my experiments, I'm not sure how to pull this one off. There are the mammary glands, uh, mammary slits of dolphins. I don't know how to milk them, but if anybody knows a marine biologist wanting to make a buck, I do have a business proposal for them. Just kidding, I'm not that shellfish. Thank you.