Uncle John knows pretty much everything—and if he doesn’t, he puts one of his many associates on the case. So go ahead, in the comments below the article, ask away. 
Why does the combination of orange juice and toothpaste taste so notoriously terrible?

It doesn’t seem like those two substances would ever cross paths—toothpaste hangs out in the bathroom cabinet, and orange juice lives over in the fridge. Except that they are both very normal parts of the morning routines for millions, and sometimes they unfortunately follow one another in close succession. Let’s say you get up, brush your teeth, and then pour yourself a glass of O.J. for a quick energy boost on the go.

Why does it taste so bad?

And that’s when your mouth is confronted with a deeply unpleasant mixture of sweet, sour, fruity, soapy, and chemical-ly. We’ve all been there. So why does orange juice post-dental hygiene taste so bad? Why doesn’t it happen with, say, water, or milk, or coffee?

Blame sodium laurel sulfate.

Most major and popular toothpastes contain a chemical called sodium laurel sulfate. It’s the active ingredient that makes toothpaste work, or rather it does a lot of the heavy lifting when it comes to cleaning your teeth. And because it’s a cleaning agent, it is, by nature, a type of soap. (It’s also what generates all that foam while you dutifully brush…you know, like soap does.)

“Under the influence” of toothpaste.

Sodium laurel sulfate also has a unique side-effect on the tongue. It surpasses the taste bud receptors that recognize sweet flavors. Orange juice, so it happens, is sweet. That means that when you’re “under the influence” of toothpaste and sodium laurel sulfate right after brushing, and you take a sip of O.J., you’re tasting what orange juice would taste like if it didn’t have any sugar in it. Only the subtle, more bitter compounds remain recognizable to the tongue. (And all in all, that makes everything taste weird.)

What can you do about it?

What’s to be done about this morning-time problem? Either wait 30 minutes to eat or drinking anything after brushing—so as to let the toothpaste “set in” without inviting damage to tooth enamel—or just switch the order. Drinking the orange juice first, and then brush. It won’t taste as weird, and you’ll also get rid of tiny sugar molecules left in your mouth.