Last week I mentioned something in passing that caught your attention: during my time in Iceland, I couldn’t help but notice how many people seemed to have broad, well-developed jaws—especially compared to what I often see in the U.S.
In Iceland, dairy isn’t demonized. It’s celebrated—and it’s different from what we find in most U.S. grocery stores.
Typical Icelandic dairy is:
- Full-fat
- Pasture-raised
- Minimally processed
- Often fermented (skyr, raw cheese, cultured butter)
Now compare that to the US: homogenized, pasteurized, low-fat dairy often stripped of fat-soluble nutrients and enzymes.
So what’s actually in this dairy that could be shaping stronger jaws?
The fat in full-fat dairy carries three key fat-soluble vitamins: A, D, and K2. These aren’t just helpful—they are essential regulators of bone growth, mineral utilization, and immune defense. Together, they orchestrate the facial development process in a way that’s so precise, it’s almost hard to believe we’ve forgotten it.
- Vitamin A ensures that cells differentiate properly and that the epithelial linings of the mouth, sinuses, and respiratory tract stay healthy and defended. It also plays a crucial role in osteoblast activity—those are the cells that build bone.
- Vitamin D increases calcium absorption in the gut and makes sure that calcium actually enters the bloodstream. Without it, all that dietary calcium passes right through you.
- Vitamin K2 is the traffic cop. It activates proteins like osteocalcin and matrix GLA protein (MGP) that direct calcium into bones and away from arteries, kidneys, and soft tissue (Beulens et al., 2013; PMID: 23525894).
Here’s what that looks like in practice: your child eats a piece of cultured, full-fat cheese. That cheese contains calcium, yes—but also vitamins A, D, and K2. The vitamin D ensures the calcium gets absorbed. The vitamin K2 ensures it gets deposited where it belongs—in the growing jaws, cheekbones, and palate—not in the kidneys or arteries. Vitamin A ensures those oral and airway tissues stay healthy and structurally sound.
Now imagine that meal without the fat. You’re missing the delivery system for these nutrients. Fat is what enables your body to absorb these vitamins—without it, they don’t make it from your plate into your bloodstream. And if you’re not getting enough of the vitamins themselves—or don’t have the microbiome to convert K1 to K2—you’re leaving development up to chance.
Worse, you may actually be putting yourself at risk. Without enough vitamin K2 to activate matrix GLA protein, calcium absorbed via vitamin D can end up in the wrong places—like arterial walls. This is what Dr. Kate Rhéaume-Bleue, author of Vitamin K2 and the Calcium Paradox, warned about: the silent calcification of soft tissues due to vitamin K2 deficiency (Rhéaume-Bleue, 2012). Over time, this can contribute to atherosclerosis, kidney stones, and stiffening of joints and tissues.
It’s not that calcium is dangerous—it’s that it needs a guide. K2 is that guide. Without it, you’re building up plaque instead of bone.
Adults benefit too: these nutrients continue to maintain strong bones, healthy gums, and resilient immune barriers. But the window for skeletal development, especially of the face and jaw, is most active in childhood—which is why this matters so much for young families.
Based on what I observed during my time there, Icelanders’ nutrient-dense traditional dairy habits may be helping preserve bone density, airway development, and facial structure—even if it’s not something they consciously recognize.
Without fat, these vitamins are harder to absorb. And let me be clear: K1 is not enough. While some gut bacteria can convert vitamin K1 (found in leafy greens) into K2, that process is inefficient and highly variable. Most people—especially those who’ve taken antibiotics, have gut inflammation, or don’t eat fermented foods—don’t convert enough K1 to meet their needs. And even when they do, it’s usually the long-chain forms (like MK-7), not the MK-4 form our bones and teeth seem to favor most. Without the right microbes, they’re harder to activate.
Let me be clear: K1 is not enough. While some gut bacteria can convert vitamin K1 (found in leafy greens) into K2, that process is inefficient and highly variable. Most people—especially those who’ve taken antibiotics, have gut inflammation, or don’t eat fermented foods—don’t convert enough K1 to cover their needs. And even when they do, it’s usually the long-chain forms (like MK-7), not the MK-4 form our bones and teeth seem to favor most.
You need pre-formed K2 from food—or from a supplement. That’s why fermented dairy, organ meats, and aged cheeses matter. It’s also why traditional diets that included these foods saw fewer issues with dental crowding, facial underdevelopment, and artery calcification.
Iceland has both: dietary K2 and a traditional diet that likely supports a healthier gut microbiome. Fermented dairy and fish provide not only nutrients but also the microbial diversity that helps optimize absorption of fat-soluble vitamins like A, D, and K2.. This microbial diversity is essential for nutrient absorption, including the enzymes and cofactors needed to fully utilize fat-soluble vitamins like A, D, and K2.
Their mineral-rich volcanic soil boosts the nutrient content of their food. And their traditional diet preserves the microbiome needed to convert vitamin K1 (from plants) to K2 (the one we need for bone and jaw growth).
But there’s one more piece of the puzzle that most people have never heard of. You might be wondering—why is this specific fat only in dairy? Why not in other full-fat foods like avocado or nuts?
Here’s where it gets even more interesting.
Full-fat dairy contains a lesser-known fat: C15:0 (pentadecanoic acid). It’s what’s known as an odd-chain saturated fat, and it’s found primarily in the fat of ruminant animals—like cows, goats, and sheep. That’s why foods like avocado, olive oil, and coconut—though nutrient-dense and full of healthy fats—don’t contain C15:0. This isn’t about fat in general. It’s about a very specific type of fat that comes from a very specific source.
C15:0 is an odd-chain saturated fatty acid—rare, and potentially essential. A 2020 study in Nature Communications proposed it may be the first new essential fatty acid discovered in decades, citing anti-inflammatory effects, mitochondrial benefits, and cellular resilience (PMID: 33099653). While more human studies are needed, early findings position C15:0 as a compelling nutrient of interest for aging and metabolic health.
Why does that matter for your mouth?
C15:0 has been shown to lower over 18 pro-inflammatory markers, including IL-6, TNF-α, and prostaglandin E2, which is linked to gum inflammation and bone loss (Nature Communications, 2020, PMID: 33099653). It also strengthens cell membranes—including those in gum tissue—and supports a more resilient, balanced inflammatory response across the body.
Most of the research so far has come from animal studies and small human trials. Promising, yes—but early. Still, the data are compelling enough to take seriously.
Personally, I’m not waiting.
Modern diets have almost eliminated this fat. In fact, one study analyzing NHANES dietary data found that over 95% of the U.S. population consumes far below the estimated beneficial levels of C15:0 (Fleming et al., 2020; Fatty15 White Paper). This is largely due to the shift away from whole-fat dairy and toward low-fat, processed alternatives over the past 50 years. Unless you’re drinking a lot of full-fat milk or eating pastured cheese daily, you’re likely not getting enough.
Rather than try to overhaul my entire diet or rely on eating large amounts of full-fat dairy every day, I’ve looked for a consistent and realistic way to reintroduce it.
So I take Fatty15, a pure, vegan-friendly C15:0 supplement.
You can read more here: fatty15.com/askthedentist
Here’s where I land after digging into all of this…
The early research isn’t definitive proof—but it’s definitely enough for me to be taking it every day.
I believe food is medicine—and high-quality, nutrient-dense food is foundational. But I’ve always supplemented. Our soil is depleted. Our schedules are packed. And unless your full-time job is cooking and nutrition, it’s nearly impossible to get everything you need from food alone. Fermented, full-fat dairy is the foundation. But let’s be honest: full-fat dairy can get caloric fast. I don’t want to rely on large quantities of it every day to get enough C15:0. Supplementation fills that gap without the extra load.
If you’re dairy-free—like my wife, who’s lactose intolerant and takes Fatty15 daily—this is one workaround. Early evidence suggests that supplemental C15:0 like Fatty15 can mimic many of the anti-inflammatory and membrane-supporting effects found in food-based sources. However, we still don’t know whether supplementation fully replicates the synergistic impact of whole foods—especially those with co-factors like vitamins A and K2. That’s an area I’d love to see more human studies explore.
If you’re raising kids? This is one of the best reasons to bring back butter.
I regret falling for the low-fat trend back in the ’90s. For a long stretch while raising our daughters, we didn’t have real butter in the house at all—just a vegetable oil spread from Trader Joe’s. My wife and I thought we were doing the right thing. Now I know better. And if I could go back and change that, I would.
But all isn’t lost. Today, functional dentists have tools like MARPE and palatal expansion to support proper airway and jaw development—even if those foundations weren’t laid in early childhood. These are structural interventions that can improve breathing, facial balance, and long-term oral health. If you’re wondering whether this could help your child (or even you as an adult), the best first step is to find a provider trained in this kind of care.
That’s why I built the Functional Dentist Directory—to connect people with dentists who understand the full-body impact of the mouth. And if you’re a dentist or hygienist interested in receiving this kind of training, my CE course—Foundations of Functional Dentistry—opens next month. It’s fully online and open to all, worldwide. I hope you’ll join the functional dentistry movement. Functional dentistry is in high demand—I get daily emails and DMs from people saying there’s not a single functional dentist within a 50-mile radius of where they live. Patients are hungry for this. If you’re a healthcare provider, you can be the one to bring it to your community.
Back to the topic at hand…I’ve always kept raw sheep cheese in my rotation because it delivers so much in one bite—vitamin K2, trace C15:0, beneficial microbes, and fat-soluble nutrients. (Choosing sheep or goat instead of cow is one “hack” to ensure you’re getting grass-fed.) And it’s delicious. I’ll have it as an hors d’oeuvre, sliced with fruit or olives—or as a small bite after dinner. Cheese helps neutralize acids in the mouth, reducing enamel erosion and supporting a healthier oral pH. It’s one of the most enjoyable (and effective) ways to protect your teeth with food.
Hope you have a wonderful weekend. Would love to hear what you thought of this newsletter, and which topics you’d like me to cover next.
Dr. B (Mark)
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P.S. Remember when we were told skim milk was the “healthier” option? What if I told you that belief may have set us back decades in understanding oral development, fat-soluble nutrients, and inflammation? Forward this to someone who still thinks skim milk is “healthier.”
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