It’s the topic that’s launched countless Internet debates: Do you brush your teeth before breakfast or wait until your orange juice and pancakes have settled before heading to the bathroom? Don’t be surprised if taking a firm stance on either side of the toothpaste line gets you some serious heat. On Reddit, home to dozens of threads on the topic, one particularly fervent fan of the “brush after you eat” method describes tackling your morning breath before your early eats as “washing your car and then immediately shoveling dirt over it.” 

“But you end up consuming all the bacteria that has accumulated on your teeth/tongue/cheeks,” counters a clearly disgusted “brush then eat” fan.

And on it goes. There are the folks who can’t imagine bellying up to the breakfast table without that minty fresh feeling, and then there’s the guy whose charming description of the taste of food after a pre-breakfast brush is “satan’s asshole.”

The chemical makeup of toothpaste is to largely blame for the latter. Most toothpastes contain a compound called sodium lauryl sulfate (SLS), a chemical known as a surfactant or a detergent that’s responsible for making toothpaste froth in our mouths. SLS tends to end up in headlines because it’s controversial: Scientists are often researching whether it’s safe for human use, and the non-profit watchdog the Environmental Working Group ranks it somewhere between low and moderate in terms of overall hazard to human health

But while most of us don’t even notice SLS in our soaps or shampoos, it makes its appearance known in a big way if we eat breakfast shortly after using a toothpaste that contains SLS. 

“The chemicals in toothpaste that make it foamy interfere with the way our tastebuds function, altering the taste of our food,” explains Dr. Jeffrey Rappaport, a NYC dentist and founder of Afora. Specifically, SLS suppresses the sweetness receptors in our mouths and destroys compounds that inhibit bitterness. So when you slug some orange juice after brushing, you’re hit with a double whammy: Your mouth can’t pick up on the sweetness, and it’s overwhelmed by the bitterness. 

The chemistry explains why some people are so adamantly #TeamAfterBreakfast, but science only goes so far in explaining why breakfast and brushing is an issue as divisive as coffee or tea. But the issue even divides dentists. hen you poll the people we all turn to for the final word on brushing, it’s impossible to find a consensus. 

They all seem to agree that food can be bad for our teeth, especially acidic breakfast faves like OJ and sugary treats like maple syrup. But their guidance for dealing with that is all over the map. 

There are the “brush before” dentists. “Brushing is aimed at removing plaque from teeth, not food,” Rapport says. “Best to just drink a big glass of water or chew sugar free gum right after eating. Floss to remove food!”

OK, easy enough. 

But then there are the “wait until after” dentists too. According to Dr. Harold Katz, it’s best to brush right after eating because mosts breakfasts are just as devastating to teeth as candy. 

“The s. mutans bacteria, which causes tooth decay, does so by converting carbohydrates into lactic acid,” the founder of The California Breath Clinics and the developer of TheraBreath, explains. That lactic acid eats through the tooth’s enamel, causing cavities. 

“The sooner food particles are removed, the better,” Katz warns. “Bacteria starts to work on food particles and carbohydrates immediately. The longer one waits, the greater chance that tooth decay bacteria will start producing lactic acid to create cavities.”

Technically Dr. Janice Scott, of Deer Park Smiles in Stockton, California, agrees with both schools of thought. Scott suggests adding a double-brushing routine into your morning. 

“The main idea is to remove plaque off the teeth,” she explains. “If you are eating sugary or processed foods, brush before and after! Brushing before leaves less bacteria around the teeth to break down the food and cause acids that deteriorate the teeth. Brushing or rinsing after will remove food debris and dilute the acids or sugar around the teeth.”

We turned to the American Dental Association for the final word on breakfast and brushing. ADA Spokeswoman Dr. Ada Cooper is neither a brush before nor a brush after dentist, nor does she think we need to double up. 

“As a practical matter, it doesn’t really matter,” Cooper says. “There’s no one size fits all. As long as you do it twice a day, whether you do it before or after is really a matter of personal preference.”

That’s the official call from the ADA, folks: Brush for two minutes, twice a day, whether it’s before breakfast or after. And if you want your bagel and schmear with a side of devil’s butthole, that’s really up to you.