Most Replayed Moment: Mouthwash REVERSES The Benefits Of Exercise! Dr Nathan Bryan

The host asks what someone should do to improve their oral microbiome. Bryan turns the question around: the most important lesson, he says, is what you shouldn't be doing. His first item is getting rid of fluoride. To back this up, he describes a dental conference in Salt Lake City "just this past weekend" where people from the US National Toxicology Program were present. He describes the program as the body tasked with running toxicology studies when there is a risk of exposure to an environmental toxicant, to find out what the risk is and whether any level is safe.

And what they report is that fluoride, there's no benefit of fluoride, and it's all risk. It lowers IQ in kids by as much as seven points, and it shuts down your thyroid function.

Bryan also calls fluoride a neurotoxin. He points to toothpaste labelling, saying that at least in the US (he says he doesn't know about other countries) the label tells you to call poison control if you swallow it. From this he concludes that "they're putting poison in toothpaste."

He then gives a dose argument. Labels advise a pea-sized amount, but he says "everybody that I know" covers the whole brush, which he estimates at 10 or 15, sometimes 20 pea-sized amounts. He puts a pea-sized amount at about half a milligram of fluoride, so heavier use would mean five or 10 milligrams. He argues that swallowing isn't needed for exposure: with a molecular weight of 19, fluoride is a small molecule that he says is absorbed directly across the lining of the mouth and becomes systemic. When the host says he'll stop using it, Bryan agrees and recommends a non-fluoride toothpaste.

Bryan backs tongue scraping. He calls it a time-tested, ancient practice and says that "even in our study" people who scrape their tongues had a more diverse oral microbiome and seemed to have better oral health. He gives no details of the study's design or size in this excerpt.

The host admits his girlfriend has been urging him to tongue scrape for two years and he has mostly ignored her. His doubt comes from what he knew about the microbiome: "should I be scraping off all my bacteria?" Bryan answers with a gardening analogy, "if you're going to plant a garden, do you plant a garden on untilled soil?" He argues that scraping breaks up the biofilm the way tilling breaks up soil, which increases microbial diversity on the back of the tongue. His technique: start at the back of the tongue, almost to the gag reflex, and pull the scraper forward. He says it should ideally be copper.

He adds a strong caveat. The worst outcome, he says, comes from combining scraping with antiseptic mouthwash. Scraping opens the tongue's surface so mouthwash can get deeper into its crypts and kill bacteria more effectively. The transcript says "in that one kid, we saw the greatest increase in blood pressure," which is ambiguous as recorded, so it's unclear which study group he means.

If you tongue scrape and use antiseptic mouthwash, that's the absolute worst scenario.