I received a request to comment on the belief of some on social media (and strangely, even a couple dentist’s websites I just looked at) that rubbing the inside surface of banana peels against your teeth will whiten them. I was specifically shown a link to a site called Quora (https://www.quora.com/How-effective-are-banana-peels-for-whitening-your-teeth) where all 8 comments posted supported the belief that rubbing banana peel against your teeth would remove stains and whiten your teeth.

My first thought was, “That’s ridiculous! No way that can be true.” But I’m a dental research scientist. I can’t just shoot from the hip. I need more information to give an educated opinion.

I wondered if maybe bananas or banana peels contain papain.

Papain is a natural proteolytic enzyme (protease). That means it’s an enzyme that breaks down (virtually dissolves) protein and other organic substances, which would include stains on the surface of your teeth. Papain is commonly derived from the papaya fruit, and one toothpaste on the market even contains papain to help dissolve tooth stains. So maybe bananas also contain papain. Let’s find out if that’s true….

I found a scientific research article in Biochemistry International, which is a journal of The International Union of Biochemistry and Molecular Biology. The article is titled, “Protease inhibitors from ripened and unripened bananas.”

The article disclosed that not only do bananas not contain papain or any other type of protease, but bananas actually inhibit the effects of papain and other proteases. So there’s the answer – bananas and banana peels have no chemical in them that has the capability to dissolve or otherwise chemically remove stains on or in teeth…period.

I wondered WHY some people claim banana peels whiten teeth.

I did more research, this time on the internet and social media, to see WHY some people claim banana peels whiten teeth.

• Some said that just the rubbing action removes the stain. Well, I suppose if you never ever brush your teeth, then yes, banana peels (or anything else you rub against your teeth) may remove at least something from the surface of your teeth. But the fact is that a toothbrush without even any toothpaste will remove far, far more “stuff” on your teeth than a soft, slippery banana peel. And when you add toothpaste to the toothbrush, that makes stain removal even more effective. So this claim is FALSE.
• Others said that Banana peel is rich in potassium, magnesium, and manganese which are absorbed over teeth surface making them appear white. As a recognized teeth whitening scientist having dealt with the science of teeth whitening since 1977, I can tell you that is absolutely false.

Both potassium and magnesium are a light silver color. Manganese is light gray. Our teeth and bones are made of hydroxyapatite (HA) molecules. Pure HA is snow-white. HA molecules are made of calcium, phosphorous, hydrogen, and oxygen atoms. Our saliva contains all of these atoms.

Every day our mouths cycle from acidic to basic (alkaline), and with these cycles, new microscopic hydroxyapatite molecules are formed on the surfaces of our teeth. If new, snow-white HA molecules formed on the surface of your teeth don’t make your teeth whiter, certainly potassium, magnesium, and manganese will not.

Maybe the claim is due to bananas being acidic and dissolving the surface of teeth, therefore, also removing surface stains.

An acidic fruit, rubbed against your teeth over and over, may make the teeth appear a little whiter because the acid would dissolve away the surface of the tooth, and of course, any surface stain would be removed along with a surface layer of your teeth. But of course, that will damage the teeth over time by dissolving the surface. So let’s look at the pH of bananas…

Foods and beverages we all consume often contain fluoride, which attaches to the HA of teeth. So at least the surfaces of our teeth have fluoride. Fluoridated tooth structure (HA) starts to dissolve at pH 4.2. Bananas are pH 4.5 – 4.7. Banana peels have an even higher pH, closer to pH 7. So bananas and banana peels are not acidic enough to dissolve HA tooth structure to make the teeth whiter.

Bottom line: Rubbing your teeth with banana peel makes your teeth whiter: FALSE