Can’t live with them – can’t live without them. And yes, I’m talking about Teeth. Did you know that chewing pressures in the jaw can have neurological effects? Here’s our first story.
Systematic reviews and meta-analyses have found that tooth loss or periodontitis is associated with both cognitive impairment and dementia. Reverse causation might be an intuitive explanation—dementia leading to a decline in oral hygiene—but prospective studies following people over time have found that tooth loss appears to predict future cognitive decline, and the more missing teeth the higher the associated risk.
Genetic determinants of elevated periodontitis risk do not appear to be associated with the development of Alzheimer’s disease, suggesting the association may be due to shared or confounding risk factors. A poor diet or low socioeconomic status represent common pathways for both tooth loss and dementia. But even studies controlling for confounding factors found a connection between tooth loss and dementia. However, one factor that wasn’t controlled for was intelligence. Those with higher IQ are both more likely to floss and have fewer tooth and gum problems, as well as have a delayed onset of clinically detectable Alzheimer’s due to a greater cognitive reserve.
Are there any potential causal mechanisms beyond the chronic inflammation? If you induce periodontitis in mice with P. gingivalis, the keystone pathogen in human periodontitis, the bacteria end up in their brains, and trigger an increase in the Alzheimer’s-associated plaque protein amyloid beta. Since then, evidence of the bacteria has been found in human Alzheimer’s brains. Clinical trials are now underway to see if blocking its neurotoxic effects will have any therapeutic benefit.
A clue to a stranger potential mechanism was unearthed in a subgroup analysis of a tooth loss and dementia meta-analysis. Only tooth loss among those without dentures was associated with the later development of dementia. The same tooth loss with dentures was not. How does that make any sense? A review entitled “Mastication for the Mind …” compiled a number of studies suggesting that chewing (mastication in medical speak) is somehow important for proper brain function. For example, the extraction of teeth from aged mice appears to upset their memory and learning. But maybe they’re just upset (in pain and inflamed) from having their teeth removed.
A more convincing series of experiments compared mice given food pellets versus the same pellets crushed into powder. Those eating the “soft” diet, the powdered diet, also suffered a loss in memory and learning capacity. What does chewing have to do with cognition? Stick an ultrasound probe on someone’s head and you can detect an increase in cerebral blood flow of the largest artery branch in the brain when they clench their jaw or chew gum. In an fMRI machine, brain scans show enhanced cognitive arousal when chewing even tasteless, sugarless gum, though translational studies on the acute cognitive effects of gum chewing are contradictory. Maybe it’s not the chewing, though.
Check this out. Noticing that people missing molars on one side of their mouths have asymmetrically sized pupils (a smaller pupil on the missing molar side), researchers tested whether implanting dental crowns to replace the missing teeth could reduce the discrepancy. And it did! The study, subtitled “New Teeth for a Brighter Brain,” suggested that a gap in the sensation of teeth pushing up against one another adversely affects brain function. To put it to the test, we’d want to randomize people with missing teeth to get dentures, and see if their cognition improves over those who don’t. No such studies exist, but there was an intriguing pilot study performed.
Ten toothless individuals, nine out of 10 of them cognitively impaired, six of them severely so, were given conventional dentures for a month before being fitted with overdentures, which are snapped into titanium implants surgically screwed into the jawbone. The conventional dentures, held in place by adhesives and natural suction, did nothing to significantly alter cognitive function. But the ones securely attached to implants in the bone (presumably transmitting the same kind of chewing pressure sensations to the nerves in the jaw that the natural roots of teeth might), had a dramatic effect. Nine out of 10 of the subjects went into the study cognitively impaired, but eight out of 10 left the study cognitively intact. This suggests well-fitting, secure dental prosthesis isn’t just about improving self-confidence, social contact, and quality of life, but proper brain functioning as well.
Of course, even better, though, would be to preserve the teeth you have.
In our next story, we look at what would happen if you stopped brushing your teeth but ate healthier?
Experimentally, if you have people stop brushing their teeth, plaque starts to build up, and within a few days the gums start to get inflamed. You can’t see anything yet, but if you take a biopsy at the gum line, you can see the inflammation starting to spread. And within a few weeks, overt gingivitis becomes apparent, where your gums can get red, swollen, and bleed easily. And if you don’t do anything about it, you can develop periodontal disease, where the inflammation creeps down into the supporting structures of the tooth—the bone and ligaments—setting you up for tooth loss. Okay, but how did we get along for millions of years without brushing? Yeah, “[d]ental disease is…almost universal” these days, but thousands of years before the invention of the toothbrush, there are skulls with perfect teeth. Now, you can say, “Yeah, but that was also thousands of years before the invention of candy bars.” But you don’t know…until you put it to the test.
Okay, yeah, but where are you going to find people to not only stop brushing but also to forego eating processed junk? Security guards. That‘s how you do it. It was one of these survivor-type TV shows where people were forced to live under Stone-Age conditions; so, no toothbrushes, toothpaste, dental floss, toothpicks, or other oral hygiene products for a month. Now, they could use a twig or something, but they were pretty much on their own. But, no candy bars either. They were going for about 4,000 BC; so, lots of whole grains, with supplemental salt, herbs, honey, milk, and meat. And then, they could go out and pick berries, or see what they could catch. So, what happened?
With no oral hygiene, their plaque built up, but their gums got healthier. This is measuring BOP, bleeding on probing (whether or not your gums bled when poked with a dental tool), a measure of gingivitis. And, in almost every case, they got better. Here are before-and-after pictures.Yeah, Lots of plaque buildup, but actually healthier gums. How is that possible? Well, mMany of the more disease-causing bacteria seemed to have disappeared from their mouths. They suggest this could be from the lack of refined sugars. But, they were eating honey; so, it wasn’t like a sugar-free diet. Ah, but what they were eating was lots of whole grains, and berries rich in antioxidant phytonutrients “with anti-inflammatory properties.” So, maybe it was a combination: sugar-intake restriction combined with the intake of really healthy foods. Thus, all those experimental studies where people stop brushing and their gums inevitably get inflamed “may only be applicable” for people eating lots of processed foods rich in sugar and low in anti-inflammatory whole plant foods.
What about “the role of nutrition in periodontal health?” Gingivitis can lead to periodontitis, “an inflammatory disease of the supporting tissues of the teeth,” which “if untreated,” can lead “to the “progressive loss of the…bone” that holds the teeth in place. Now, part of the development of periodontal disease may involve oxidative stress. So, not only do we need to reduce our intake of pro-inflammatory foods like refined carbs and saturated fats, maybe it would help if we sought out foods that are antioxidant-rich.
So, is there an association between dietary vitamin C intake, for example, with periodontitis? Apparently so, with increasing risk of periodontitis associated with lower levels of vitamin C intake. But you don’t know…until you put it to the test to figure out what effect vitamin C depletion and supplementation would have on periodontal health. They basically locked everyone up for three months so they can provide controlled amounts of vitamin C and…“measures of [gum] inflammation were directly related to their [vitamin C] status.” On about one orange worth of vitamin C, their gums improve, but then down to 5 mg a day, they got worse. But then on 10 oranges’ worth a day, they got better, then worse again when back down to 5. Pretty convincing, though 5 mg a day is like scurvy level. I mean, we know that your gums start bleeding and your teeth can fall out when you have scurvy, but that doesn’t mean taking extra helps.
And indeed, 1,500 mg of vitamin C a day did not seem to help prevent gingivitis. And even 2,000 a day failed to help periodontitis sufferers. Maybe vitamin C is just too weak of an antioxidant? Okay, what about lycopene, the powerful antioxidant pigment that makes tomatoes red? It worked! But that was from injecting the stuff directly into the gum pocket with a syringe. Does it work if you just eat it? Let’s find out.
“A randomised, placebo-controlled clinical trial” on the “efficacy of lycopene in the treatment of gingivitis.” Two weeks of less than a single tomato-a-day’s worth of lycopene versus placebo for two weeks, both along with the standard dental treatment, which helped—a 10 to 20 percent reduction in gingivitis in the placebo group, but nearly 30 percent improvement within just one week in the lycopene group. And this was just like the amount of lycopene found in a teaspoon and a half of tomato paste a day. Totally doable. Okay, so tomatoes may help with gingivitis. What about periodontitis?
Another randomized, double-blind, placebo-controlled trial again treated with the usual dental cleaning plus either that one tomato-a-day’s worth of lycopene or a placebo for two months, and significant improvements in plaque gingivitis and bleeding, though not probe pocket depth and clinical attachment. You can see the difference. See how much better their gums look. They conclude that “[s]upplementation with lycopene seems to have augmented the healing sequence of inflamed gingival tissues.” Okay, but that was with a whole tomato’s worth a day. How about half-a-tomato’s worth, or just three-quarters of a teaspoon of tomato paste worth of lycopene a day? It didn’t work; no difference, so looks like you have to go the whole tomato.
Finally today, plant-based diets are put to the test in the treatment of periodontal disease.
What is the effect of nutrition on periodontal disease? “Periodontal disease is a bacterial infection that results in inflammatory destruction of the connective tissue and bone that support the teeth,” and is therefore “one of the leading causes of” our teeth falling out. Like most infections, though, how our body responds may play a critical role. Yes, “the presence of bacteria is the primary [cause, but] a susceptible host is also necessary for disease initiation.”
The standard explanation of periodontal disease is the plaque theory: the build-up of plaque leads to gingivitis—gum inflammation—which leads to the periodontitis, inflammation lower down beneath the gums. But in some forms of periodontal disease, plaque doesn’t appear to play a critical role. Therefore, in the last few years, there has been more interest in the importance of systemic health, our body’s response. “In this respect, nutrition may be of great importance, since it has been implicated in a number of [other] inflammatory diseases”—all of which carry elevated periodontal disease risk.
Traditionally, when we think of the effects of nutrition on dental diseases, we’re only thinking about cavities. However, there’s been less research on the role of diet in periodontal diseases. Well, but if it’s about inflammation, one would expect “saturated fat-rich diets” to make things worse—increasing oxidative stress as well inflammation. So, we may want to cut down on saturated fat. But let’s not just speculate. I mean, is there an association between cholesterol levels and periodontitis? If not, it would be hard to implicate saturated fat. But no, there does appear to be a link. Those with high cholesterol do appear to have up to double the risk.
What about periodontal conditions in vegetarians? A hundred vegetarians versus non-vegetarians were studied, and those eating vegetarian did have “better periodontal conditions (less inflammation signs, less periodontal damage, and better dental home care).” However, it should be considered that vegetarians may not just be avoiding meat, but are healthier in other ways, like better dental home care.
But do people who eat more saturated fat get more periodontitis? Yes, about double the risk at the highest levels of intake. And this study was in Japan, where they eat less than half the meat and dairy compared to the U.S. The only way to know for sure, though, is to do an interventional trial, where you change people’s diets and see what happens. In other words, you have to put it to the test. And, bone loss was indeed magnified by a diet high in saturated fat and cholesterol. But if you’re thinking hmm…that’s a weird-looking jaw, that’s because it was a study done on rats.
“A high-fiber, low-fat diet improves periodontal disease markers” in terms of probing depth, clinical attachment loss, and bleeding on probing—all the standard measures. And, of course, eating a healthier diet, body weight, blood sugar control, and systemic inflammation improved as well. Ah, but that complicates things. Maybe their mouths got better just because they lost so much weight. You can improve periodontal disease with just bariatric surgery, like stomach stapling. Well, after eight weeks on the diet, they went back on their regular diet, and so gained most of that weight back. But the periodontal disease improvements persisted, suggesting that it was more than just the weight loss that lead to the improvements. They’re thinking maybe the high-fiber diet altered their good gut flora, or maybe their oral flora? What exactly was going on?
Well, German researchers took 20 women with mild-to-moderate chronic periodontitis, and for a year, tried to transition their diets towards more wholesome nutrition—meaning more plant foods, more whole foods, more fresh foods, trying to center their diets around vegetables and fruit, whole grains, potatoes, and legumes—beans, split peas, chickpeas and lentils. And after 12 months, the patients “showed a significant reduction of probing pocket depth, gingival inflammation and, [measured for the first time,] decreased concentrations of inflammatory” chemicals inside the crevice between the tooth and gums, which are thought responsible for “the tissue destruction in periodontal disease”—a decrease by as much as 75 percent. And, all the while, their “oral hygiene status did not change,” suggesting it was the diet that did it.
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