A Conversation for Ask h2g2

Grapefruit and toothpaste

Post 1


Here's a breakfast-time conundrum. If you brush your teeth, using a minty toothpaste, and then drink a glass of grapefruit juice, it produces what I suppose you'd call a "rush". You get a lovely tingling sensation in your mouth. I've tried it with other citrus beverages (orange, FiveAlive, etc.) and it only works with grapefruit.

The non-grapefruit juice drinkers in my household just don't understand. But I need to know. What causes this effect? Is all down to a chemical reaction? And is it bad for me?

Grapefruit and toothpaste

Post 2

Lonnytunes - Winter Is Here


If drinking red wine (especially younger wine) they have the effect of turning your tongue and teeth black.

No.smiley - bigeyes

Grapefruit and toothpaste

Post 3


Awesome. I have to try that.

Grapefruit and toothpaste

Post 4


Although, of course, drinking citrus juice of any type, and then brushing your teeth within roughly the next half hour, *is* bad for you.

IIRC, the citric acid temporarily makes the enamel ~1000 times softer, so if you do this habitually, you'll wear down your teeth.


Grapefruit and toothpaste

Post 5


People attempting funny stuff with their teeth should ensure that they either live or were brought up in Durham, where the fluoride content of the water kicks ass. May I also recommend Dentyl mouthwash, which tastes nice and doesn't rip the shit out of your gums upon usage. Normal mouthwashes work on the chemotherapy principle whereby they aim to kill the bacteria in your mouth (or at least suppress them as they're there to stay) slightly before they eat away your gums.

Grapefruit and toothpaste

Post 6


Oddly enough, I *was* brought up in Durham, so must have been chemically favoured from birth to participate in citrus-orientated dental activities.

I'll probably die of fluoride poisoning, but hey! At least I had some larks...

Grapefruit and toothpaste

Post 7

Lonnytunes - Winter Is Here

Lark pie, with or without toothpaste, is wonderful

Grapefruit and toothpaste

Post 8


I believe it is a basic neutralization reaction (there may be other stuff but I barely passed AP Chem) For those of you who don’t know: Acids and bases are such because they contain either H+ (read Hydrogen positive) or OH- (read Hydroxide negative) in the molecular structure. Thus water as a neutral compound is H-O-H, or H2O. When Acids (H+ donors) and Bases (H+ receptors) mix what is known as a neutralization reaction occurs, the H+ are released into the base, and fizzing occurs, usually it smells awful as well. My Colgate (Clean mint flavor/Deep cleaning formula) contains Sodium Hydroxide (NaOH, notice the “OH” it is a base) and grapefruit juice contains citric acid of some sort, I don’t know the formula but lets call it HXx (notice the H part, making it acidic) When you brush then drink the reaction happens in your mouth like this HXx + NaOH -----> NaXx + H2O + (energy released) the NaXx part is probably pretty stinky and tastes funny, while the energy released (in bubbly form) makes your tongue tingle. Or for the lay person, remember the vinegar / baking soda volcano, that’s what’s happening, only this time you’ve gotten to satiate the urge to taste it.


P.S. If someone with a chemistry degree, or even someone with a better teacher than I had wants to correct me I’d be thrilled to hear it.

Grapefruit and toothpaste

Post 9

Lonnytunes - Winter Is Here

...and now explain h2g2 smiley - fish

Grapefruit and toothpaste

Post 10


Ah-ha! Mystery chemically explained. Thanks for that, Alan.
BTW, if you try the same trick with orange juice and toothpaste, it does taste somewhat horrid and stinky. But for some reason, grapefruit (not being quite so nice-tasting to start with) is vastly improved by a load of neutralization going on in your mouth...

Grapefruit and toothpaste

Post 11


whereas marmalade and toothpaste taste like badger shit. who designed mornings?

PS ta for the superchicken info.

Grapefruit and toothpaste

Post 12


The biggest danger in my household for me is the morning-after a full moon - I fear of the juice-squeezer in those mornings, believe me!

Grapefruit and toothpaste

Post 13

Oot Rito

Just going out to buy some grapefruit juice...... yes, I already have toothpaste thank you

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Grapefruit and toothpaste

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