I’m taking on sinus inflammation because it’s a major contributor to my motion sickness, which is a major contributor to making commuting suck, and commuting is one of very few things that can actually depress your hedonic set point (psychologist talk for “make you miserable”). My doctor has suggested xylitol nasal spray, which she claims inhibits irritation in the sinus cavities. Quick googleing reveals it’s also considered useful for bacterial plagues on the teeth and in the arteries. Let’s dig in.
Xylitol’s main claim to fame is as a calorie-less sweetener in humans. The claim is that it kills (many but not all strains of) bacteria via the same mechanism: it can’t be converted into energy, so the bacteria starve to death. This has to be to be missing a step. Bacteria are surrounded by billions of molecules they can’t digest all the time, and they survive that. If xylitol is to have an affect it must not only be indigestible, but inhibit digestion of actual sugar. Off the top of my head there’s two ways that could happen. In the human body, sugar is moved around by the blood. If xylitol takes a sucrose molecule’s ticket to a particular area, there will be less sugar there for bacteria to eat. The downside of this is that you might starve out your own cells. Another option is that bacteria cells themselves become confused by xylitol. The ideal would be if xylitol fit into a sugar receptor but couldn’t be taken into the cell, so the receptor was blocked indefinitely. Or if it was taken in it could trigger a “yup, we got a sugar” reaction that caused the cell to take in sugar later, but I’m not sure why a bacteria would ever turn down calories.
I found a lot of studies on xylitol and dental use. Most of what I learned is that dental abstracts are more like teasers than summaries, not cluttering up the space with numbers or sometimes even conclusions. Overall there seems to be a mild consensus for xylitol mildly inhibiting cavities, although it’s certainly not a substitute for fluoride. Also I totally should have been chewing xylitol while I was recovering from surgery, since is almost certainly disrupts oral plaques, although I worry about what it would do to the intestinal biome.
What about sinuses? I found a lot of very small studies, but 5 studies of size n are not equivalent to one study of size 5n. You don’t know how many more studies of size n were done but not published.
This study and this one found decreases in medical severity (as measured by the SNOT-20 score. Yes that’s it’s real name), but not self-reported pain (as measured by the less well named VAS score). This study in rabbits was well controlled (if small) and found significant decreases in bacteria.
This study found that a nasal decongestant spray worked better than xylitol or saline spray, which worked about equally as well. Nontheless it’s conclusion was that [name brand of xylitol spray] was an effective treatment for nasal congestion. It also spelled spray with an ‘e’ . Twice.
One interpretation of these results is xylitol helps impedes infection but irritates the sinuses such that there’s no change in pain levels. Another is that people are really good at suppressing conscious knowledge of pain. My experience has been I’m really good at suppressing moment-to-moment awareness of pain but I do notice when asked (which is how I went weeks without treating my dental neuralgia, and then suddenly noticed I was at 8 on the pain scale), and that the pain has a great deal of effect on my behavior and happiness whether I acknowledge it or not. And if I keep using xylitol I need to change my brand to one that, when it buys positive press in a supposedly objective forum, spells its own name correctly.