HoldsUp

Dr. Ellie Phillips · 2026-02-02 · Ellie Phillips (host)

“Everything I knew about dentistry - you turned it on its head” - Dr. Ellie with Ask A Hygienist

32 research-tied claims examined: 4 contradicted 3 overstated 3 context 11 supported 11 unverified

11

Supported by research

0:08:40Ellie Phillips (host)supportedmoderate

Acidifying the mouth enhances the remineralization capacity of fluoride.

"And I knew that if you had this acidic Listerine followed by the fluoride, a dilute sodium fluoride, that it would enhance the mineralization of the fluoride. It's part of that idea in pediatric dentistry. Back in the day, we used to use these acidified fluoride gels. They were way stronger. But one of the points of acidifying the mouth is to make the remineralization more intense." (said at 0:08:40)

Dental literature confirms that acidic pH enhances fluoride uptake and remineralization efficacy on dental enamel. Historically and in clinical practice, acidulated phosphate fluoride (APF) formulations (typically around pH 3.0 to 5.5) were developed because transient acidity increases enamel surface reactivity and promotes the deposition of calcium fluoride-like reservoirs, which subsequently release fluoride to aid remineralization. In vitro pH-cycling studies evaluate this mechanism and show that slightly acidified fluoridated formulations improve surface microhardness and decrease lesion porosity more effectively than neutral formulations.

0:11:20Ellie Phillips (host)supportedmoderate

Gut bacteria can change in two weeks following a dietary shift, as shown in studies of tribal populations.

"Digestive bacteria are a lot more interchangeable and affected and they you can actually change the gut bacteria in a couple of weeks with a change of diet. They've proven that in, you know, tribal sort of cultures where they eat very different things. People, you know, have taken fecal samples and seen the change in in two weeks and then when they go back to a western diet, doesn't take long to change back." (said at 0:11:20)

Controlled dietary intervention studies confirm that human gut microbiota composition and metabolic activity change rapidly within days to two weeks of a dietary shift. In a landmark 2-week reciprocal food exchange study between rural South Africans consuming a traditional high-fiber diet and African Americans consuming a high-fat Western diet, switching diets for just two weeks produced substantial reciprocal shifts in gut microbial community composition, short-chain fatty acid production (including butyrate), and secondary bile acid metabolism. Additional controlled feeding studies demonstrate that gut microbial community structure shifts significantly within 1 to 4 days of switching between plant- and animal-based diets and reverts quickly upon return to baseline intake.

  • supports: Diet rapidly and reproducibly alters the human gut microbiome. (Nature 2014) · cited 10361x in the literature
    "Here we show that the short-term consumption of diets composed entirely of animal or plant products alters microbial community structure and overwhelms inter-individual differences in microbial gene expression... In concert, these results demonstrate that the gut microbiome can rapidly respond to altered diet, potentially facilitating the diversity of human dietary lifestyles." (abstract, results, passage verified)
    pubmedfull study (doi)
  • supports: Fat, fibre and cancer risk in African Americans and rural Africans. (Nature communications 2015) · cited 1001x in the literature
    "We performed 2-week food exchanges in subjects from the same populations, where African Americans were fed a high-fibre, low-fat African-style diet and rural Africans a high-fat, low-fibre western-style diet, under close supervision. In comparison with their usual diets, the food changes resulted in remarkable reciprocal changes in mucosal biomarkers of cancer risk and in aspects of the microbiota and metabolome known to affect cancer risk, best illustrated by increased saccharolytic fermentation and butyrogenesis, and suppressed secondary bile acid synthesis in the African Americans." (abstract, results, passage verified)
    pubmedfull study (doi)
0:22:25Ellie Phillips (host)supportedhigh

Periodontal chronic inflammation can be measured systemically as an elevation in HbA1c and C-reactive protein (CRP) levels.

"And chronic inflammation, you're absolutely correct, is something stuck under the gum, likely some hardened calculus that's causing this chronic inflammation that's creating a ripple effect that is causing inflammation. You can even read in the body inflammation as a rise in A1C and CRP levels and I mean you can actually measure it." (said at 0:22:25)

Substantial evidence from randomized clinical trials and systematic reviews confirms that chronic periodontal inflammation produces measurable systemic effects, notably elevated systemic inflammatory markers such as C-reactive protein (CRP/hs-CRP) and higher glycated hemoglobin (HbA1c). Systematic reviews and meta-analyses show that treating periodontal disease through scaling and root planing leads to statistically significant reductions in both serum CRP and HbA1c levels.

0:29:55Ellie Phillips (host)supportedmoderate

Denmark does not fluoridate its public water supply.

"and in a place like Denmark, I mean, you can look this up, the the countries with the top oral health in the world, they don't fluoridate their water supplies." (said at 0:29:55)

Denmark and other Nordic countries do not practice community water fluoridation, relying instead on public dental healthcare systems and self-performed topical fluoride exposure (primarily brushing with fluoride toothpaste) to achieve and sustain low dental caries levels across their populations.

0:25:20Ellie Phillips (host)supportedhigh

Saliva is naturally supersaturated with the minerals needed to repair and remineralize teeth.

"the greatest thing about saliva is that it is usually supersaturated. That means it's dripping with the minerals that your teeth need." (said at 0:25:20)

The claim is supported by dental and oral physiology literature. Saliva is normally supersaturated with respect to tooth mineral (hydroxyapatite), containing calcium and phosphate ions that drive remineralization and prevent demineralization under neutral pH conditions.

0:11:27Ellie Phillips (host)supportedhigh

The bacterial composition of the oral microbiome is distinct from and not similar to the gut/digestive microbiome.

"although some digestion goes on in the mouth, the bacteria of the mouth are not similar to the digestive bacteria." (said at 0:11:27)

Published metagenomic and cross-body site microbiome research consistently confirms that the bacterial community of the oral cavity is distinct from that of the lower digestive tract (gut/fecal microbiome). Comparative profiling demonstrates that body habitat is a primary driver of microbial composition, with oral and gastrointestinal niches harboring distinctly differentiated bacterial taxa, functions, and transmission dynamics.

0:29:44Ellie Phillips (host)supportedmoderate

In Nordic countries such as Finland, preschools routinely distribute xylitol chewing gum to children after lunch and before going home.

"They actually hand out xylitol gum in preschool in these countries as the children arrive after lunch and before they go home." (said at 0:29:44)

The claim is supported. In Finland, the distribution of xylitol chewing gum and pastilles in preschools and daycare centers is a well-established oral health measure used routinely across daycare centers following meals, supported by national oral health guidelines and evaluated in community trials investigating xylitol gum programs in Finnish daycare settings.

0:34:48Ellie Phillips (host)supportedmoderate

The human body produces approximately 15 grams of xylitol endogenously per day.

"It makes about 15 grams of xylitol daily. Not all in one go, very spaced out throughout the day because xylitol helps us to actually keep our glucose levels in check." (said at 0:34:48)

The human body produces xylitol endogenously as an intermediate of carbohydrate metabolism, specifically via the D-glucuronate-L-xylulose pathway and pentose phosphate pathway, with classic human metabolic studies estimating endogenous synthesis at approximately 5 to 15 grams per day. The host's statement accurately reflects this physiological figure and describes its role as an intermediate in normal human glucose and polyol metabolism.

0:35:25Ellie Phillips (host)supportedmoderate

Xylitol is fermented in the digestive tract to form butyrate, a protective short-chain fatty acid.

"it will just go down with your food and it forms butyrate, which is a short-chain fatty acid that is actually protective of our gut lining." (said at 0:35:25)

Xylitol is a low-digestible carbohydrate that reaches the large intestine, where it is fermented by commensal gut microbes (specifically species of Anaerostipes, such as Anaerostipes hadrus) into short-chain fatty acids, predominantly butyrate. Butyrate serves as a major energy source for colonocytes and is well-established to support gut barrier integrity and mucosal health.

0:41:54Ellie Phillips (host)supportedmoderate

Tea leaves concentrate fluoride from the soil, resulting in brewed tea containing approximately three parts per million of fluoride.

"If you drink tea, tea has about three parts per million because most tea, right, is created harvested. I don't know how you say it in in India, right? And India is in China and Japan where there's fluoride in the soil... It's just that the tea tree actually, you know, condenses it into the leaves." (said at 0:41:54)

Published analytical studies and reviews confirm that the tea plant (Camellia sinensis) is a hyperaccumulator of fluoride from acidic soils, storing high concentrations primarily in its mature leaves. In brewed infusions, fluoride levels typically range from approximately 1 to 5 mg/L (equivalent to parts per million or ppm), with black tea infusions averaging approximately 2.3 to 2.8 mg/L and brick tea averaging ~4.8 mg/L depending on brewing time and tea type.

0:55:35Ellie Phillips (host)supportedhigh

Dental fluorosis was first discovered in the late 19th or early 20th century by a dentist in Colorado Springs observing endemic brown-stained teeth among local residents.

"Well, the first thing is if you look back at the story of fluoride, how it was found, it was in the 1900s, late 1800s, early 1900s, a dentist in Colorado, actually in Colorado Springs, noticed that all the patients in his office had brown-stained teeth. That's how the the whole fluoride story begins right there in Colorado Springs." (said at 0:55:35)

Historical records in dental literature confirm that the scientific investigation into dental fluorosis and water fluoridation began in Colorado Springs in the early 20th century. Dentist Frederick McKay opened a practice in Colorado Springs in 1901 and observed widespread, severe brown staining on the teeth of local residents (known locally as the 'Colorado Brown Stain'). McKay's investigations, in collaboration with G.V. Black and subsequent water chemistry analyses by H.V. Churchill, ultimately established that high natural levels of fluoride in local drinking water were the cause of this dental fluorosis.

  • supports: History of Dental Fluoride (Kaleidoscope History 2025)
    "However, it was Frederick McKay’s investigations in Colorado Springs that led to the recognition of fluoride’s role in both staining and protecting teeth from decay. His collaboration with G.V. Black and later research by H.V. Churchill confirmed that high fluoride levels in drinking water caused fluorosis but also resulted in lower rates of dental caries." (abstract, passage verified)
    openalexfull study (doi)

Unverified means no publication matching the claim was located; it does not prove the claim false. Spotted an error? See the corrections policy - disputes from the people quoted are prioritized.