 Sodium laurel sulfate had already been used as a foaming agent in toothpaste for more than a half century by the time this study was published, which showed tissue damage in most of those who had it smeared on their gums, but most of just 10 people. The same with the study that showed a dramatic decrease in the number of canker sores when switching to an SLS-free toothpaste. Just 10 people. But that's all we had, until 1999, in a randomized, double-blind crossover trial was published SLS versus non-SLS toothpaste in not just 10 people, but 47 people with recurrent canker sores. Looking at the number of days suffering, total pain, number of ulcers, how long they lasted, how big they were, and no significant differences were noted. It didn't seem to matter whether the toothpaste had sodium laurel sulfate or not, but what about the study showing the 70% decrease? Well, maybe it's because those cases were worse, and so the type of toothpaste only matters if you have really bad canker sores. And that's where the science ended, until 13 years later, when Korean researchers picked up the torch. We had studies showing SLS-free toothpaste helps. We had other studies that found no benefit, leading to considerable controversy. And so they launched the biggest study to date, 90 subjects, and same number of ulcers and ulcer episodes, but the duration they lasted for, an average pain score was significantly less when they were using the SLS-free toothpaste. So switching to an SLS-free toothpaste may not reduce the number of canker sores you get, but it may allow them to heal faster and make them less painful. So yeah, sodium laurel sulfate can create an impression of cleanliness, it's a mouthful of foam just feels cleaner, but there may be a downside, potentially reducing the protective barrier of our mouth lining, probably due to the rupture of the bonds that hold our cells together, sometimes causing sloughing, ulcerations, and inflammation, drying out the protective mucus layer lining our mouth, making us more vulnerable to irritants. But wait, how did they explain that their study found a problem, but the last study didn't? They suggest it could be a race issue. What? Well, they explained Koreans tend to love their spicy food, and so maybe that makes a difference. Regardless, if you get canker sores, you may want to give an SLS-free toothpaste a try to see if it makes any difference in your case. But non-SLS toothpaste may just have other detergents, most commonly cocomitopropyl betaine. Is that any better? Well, what these Swiss researchers did was just take nine toothpaste, Colgate, Crest, Oral-B, Sensodyne, etc., and drip them on some human gum cells taken fresh from people who had their wisdom teeth extracted, and then used live dead cells staining. Basically, you stain all cells green, and then you add a red dye that covers up the green, but only in dead cells, because the live cells actively pump out the red dye. So then live cells stay green, but dead cells turn red. Let's see if you can guess if Colgate has SLS in it. All red, all dead. What about Crest? Mostly red, mostly dead. But guess if Sensodyne has SLS in it? All green, all alive. And indeed, it has the SLS-free detergent CAPB instead. What about Oral-B? SLS or no? Versus this one. This one. Or this one. It seems pretty clear which is which. But that's in a petri dish. Does that translate out into actual tissue damage in people? A double-blind crossover study, SLS-containing toothpaste versus CAPB-containing toothpaste. 42 disquamative reactions, meaning tissue-peeling reactions after four days at four minutes a day of the SLS toothpaste on their gums, compared to just three with the alternate detergent, and no such reactions at all using the exact same toothpaste, but with just no detergents at all, neither SLS nor CAPB. How does that translate out into cankersoar frequency? How about a randomized double-blind crossover study to investigate the effects of toothpaste containing SLS versus CAPB versus no detergent at all? They found significantly higher frequency of cankersoars when patients brushed with an SLS-containing toothpaste than with a non-SLS-containing toothpaste. So they suggest that SLS-free toothpaste be recommended for patients with recurrent cankersoars. But they found more than just that. Yes, SLS was the worst, but the non-foaming toothpaste, the detergent-free toothpaste, beat them both out. The non-foaming toothpaste caused significantly fewer ulcers than the non-SLS alternative detergent CAPB, which in turn caused significantly fewer ulcers than the SLS toothpaste. So the vast majority of recurring cankersoar patients would benefit from switching from a regular toothpaste to a non-foaming toothpaste, but most would benefit just staying away from the SLS regardless. But if your toothpaste doesn't have sodium laurel sulfate, will it work as well? I'm not just talking about the impression of cleanliness, but actual like plaque and gingivitis. Yeah, SLS may kill our cells, but also kills bacteria cells. So might SLS-free toothpaste not work as well? We didn't know until now. And it turns out the SLS-free toothpaste worked just as well with regard to reducing gingivitis and plaque, and so it can be recommended for those with recurrent cankersoars. Since sodium laurel sulfate may make things worse by disintegrating the protective mucous layer and eventually penetrating the deeper layers of the lining of our mouth where living tissue function may be compromised. However, folks did miss the foaminess. Though there is one additional benefit to choosing SLS-free toothpaste, SLS also penetrates into our tongue and interferes with the inner mechanisms of our taste cells. Sodium laurel sulfate is what's responsible for the orange juice effect. That weird tasty get from citrus right after you brush? SLS is evidently what's mucking with your taste cells.