You might be thinking that the idea why toothpaste makes liquids like orange juice taste so terrible is simply due to the traditional mint flavor of toothpaste mixed with other flavors, but this isn’t exactly what’s happening here.
The real culprit was thought to be the two compounds almost universally added to toothpaste -sodium lauryl ether sulfate and sodium lauryl sulfate, which are anionic surfactants, meaning they decrease the surface tension of water.
Why is that desirable in toothpaste anyway? Because it works like a detergent and makes the toothpaste to foam so as to help it spread inside your mouth much easier. Besides any other cleaning effect, this has the by-product to make you feel like the toothpaste is doing something awesome, which toothpaste producers have found to be an excellent way to get people to buy more of their toothpaste. Smart right.
Mint is also added to toothpaste for this same effect, as it leaves your mouth feeling cool, feeling fresh and clean, particularly if it’s well dispersed inside your mouth.
People need some kind of signal to know that a product is functioning. We can make toothpaste taste just like anything — blueberries, green tea — and as long as it has a refreshing tingle feeling about it, people feel like their mouth is automatically clean. The tingling feeling doesn’t make the toothpaste to work any better. It just convinces people it’s doing the job perfectly.
(Interestingly enough, besides any real cleaning effect, sodium lauryl sulfate is also added to shampoo for the same marketing reasons, as many people believe that foaming shampoo works better than non-foaming shampoo, whether or not a specific brand’s foaming shampoo actually cleans better than some other non-foaming shampoo.)
Back to your taste buds -the sodium lauryl sulfate cooperates with your sweet taste receptors, making them less sensitive, and consequently lessening the sweet flavor. In addition, it also exterminates phospholipids in your mouth, which are compounds that have a similar type of effect sodium lauryl sulfate has on sweet taste buds, except the phospholipids deadens your bitter taste buds.
The net effect is that your bitter taste buds become more sensitive while your sweet taste buds are dampened. So when you drink something like orange juice, which naturally should have an overpowering sweet taste that covers an underlying bitter taste, it is going to taste drastically different -in this situation extremely bitter.
So if for any reason your morning routine inevitably includes brushing your teeth before eating, you can easily find a toothpaste that is free of sodium lauryl sulfate, and sodium lauryl ether sulfate and the food you eat directly after shouldn’t taste obnoxious, unless you’re bad at cooking, of course.