For those with recurrent canker sores, is it better to use a toothpaste with SLS, CAPB, or no foaming agents at all?
Sodium lauryl sulfate (SLS) had already been used as a foaming agent in toothpastes for more than a half-century by the time a study was published showing tissue damage in most of those who had it smeared on their gums—but that was “most” of only ten study subjects. Same with a study finding a dramatic decrease in the number of canker sores when people switched to an SLS-free toothpaste. (Again, just ten people.)
But, that’s all we had until 1999, when a randomized, double-blind, crossover trial was published, testing SLS against non-SLS toothpaste in not just 10 people, but 47 people, with recurrent canker sores. The study looked at the number of days of suffering, total pain, number of ulcers, how long they lasted, and how big they were, and no significant differences were noted. It didn’t seem to matter whether the toothpaste had sodium lauryl sulfate or not. But what about that study showing the 70 percent decrease in canker sores after switching to an SLS-free toothpaste? Well, maybe those cases were worse and the type of toothpaste used only matters if you have really bad canker sores?
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 and other studies finding no benefit, leading to “considerable controversy,” so they launched the biggest study to date with 90 subjects. What did they find? The same number of ulcers and ulcer episodes among the groups, but the duration the ulcers lasted and average pain score were significantly decreased when subjects were using the SLS-free toothpaste. So, the researchers concluded that 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, yes, sodium lauryl sulfate “creates an impression of cleanliness, and a mouthful of foam ‘just feels cleaner,’” but the potential downside may be that “SLS reduces the protective barrier of the oral epithelium,” our mouth lining, probably due to the rupture of the bonds that hold our cells together. This can sometimes cause sloughing, ulcerations, and inflammation that dry out the protective mucous layer lining our mouth, making us more vulnerable to irritants.
Hold on. How did the Korean researchers explain that their study found a problem, but the previous study didn’t? They suggested it could be a race issue. Really? Well, they explained that “Koreans eat more hot and spicy food,” so maybe that makes a difference?
Regardless of how spicy you like your food, if you get canker sores, you may want to give an SLS-free toothpaste a try to see if it makes any difference for you—but non-SLS toothpaste may just have other detergents, most commonly cocamidopropyl betaine (CAPB). As I discuss in my video, Is CAPD in SLS-Free Toothpaste Any Better? Swiss researchers took nine toothpastes, including Colgate, Crest, Oral-B, and Sensodyne, and dripped them on some human gum cells taken fresh from people who had their wisdom teeth extracted. They then used live-dead cell staining: All the cells were dyed green, and then a red dye was added that covers up the green dye, but only in dead cells, because the live cells actively pump out the red dye. So, the live cells stay green, but the dead cells turn red. As you can see at 3:25 in my video, Colgate contains SLS because the cells are all red and all dead. And Crest? The cells are mostly red and mostly dead. But with SLS-free Sensodyne, the cells are all green and all alive because it contains the SLS-free detergent CAPB instead.
But that was in a petri dish. Does that translate out into actual tissue damage in people? A double-blind crossover study of SLS-containing toothpastes versus CAPB-containing toothpastes found 42 desquamative reactions, meaning tissue peeling reactions, after four days of four minutes a day of the SLS toothpaste on subjects’ gums, compared to just three reactions with the alternate detergent, CAPB. And there were no such reactions at all using the exact same toothpaste with no SLS or CAPB at all—detergent-free toothpaste.
How does this translate out into canker sore frequency? A randomized, double-blind, crossover study investigated the effect of toothpastes containing SLS, CAPB, or no detergent at all. The researchers found “significantly higher frequency” of canker sores when patients brushed with SLS-containing toothpastes rather than with non-SLS toothpastes, whether CAPB-containing or detergent-free, so they suggest that an “SLS-free toothpaste may thus be recommended for patients with recurrent aphthous ulcers,” canker sores. But, as you can see at 5:00 in my video, they found more than just that.
Yes, SLS was the worst, but the detergent-free, non-foaming toothpaste beat out both SLS and CAPB. Indeed, 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 recurrent canker sore patients would benefit by switching from a regular toothpaste to a non-foaming toothpaste, but most would benefit by staying away from SLS regardless.
But if your toothpaste doesn’t have sodium lauryl sulfate, will it work as well? I’m not just talking about “the impression of cleanliness,” but actual effect on plaque and gingivitis? SLS may kill our cells, but it also kills bacteria, so is it possible an SLS-free toothpaste won’t work as well? It turns out that SLS-free toothpaste works just as well “with regard to reducing gingivitis and plaque,” so we can recommend it for those with recurrent canker sores. Sodium lauryl sulfate may make things worse by disintegrating the protective mucus layer and eventually penetrating into the deeper layers of the lining of our mouths, where “living tissue function may be compromised.”
Folks did miss the foaminess, though, of a toothpaste with SLS. 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.” It’s actually responsible for the “orange juice effect.” You know that weird taste you get from citrus right after you brush your teeth? SLS is evidently what’s mucking with your taste cells.
Sodium lauryl sulfate? Wasn’t that part of some internet hoax? I cover the background of that in my video Is Sodium Lauryl Sulfate Safe?.
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Michael Greger, M.D.
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Published at Tue, 06 Apr 2021 12:00:29 +0000