This Type of Coffee Is the Least Likely to Stain Your Teeth, According to Science
The way your coffee is roasted stains your teeth differently.
For all the good coffee does, it’s not easy on our teeth. The components in our favorite morning beverage can discolor our pearly whites with every sip. However, not all coffees stain equally. And it turns out that one type of coffee will induce far less teeth discoloration than the rest.
Based on how they’re roasted, some coffees are more prone to tinting our teeth than others. While it might seem counterintuitive, light-roast coffees are, in fact, the worst offenders when it comes to staining our teeth.
Breaking down the acidity
On the pH scale, which measures a substance’s acidity, coffee tends to sit on the acidic end. (For reference, water is completely neutral at 7 on the 0 to 14 scale.) Coffee has a pH between 4.9 and 6.2, according to Monica Bebawy, a dentist at the New York University College of Dentistry.
Your teeth are vulnerable to acidic compounds. “Enamel is a super hard substance, but actually porous,” Bebawy tells Inverse. If you enjoy a food or drink with a pH of 5.5 or lower, the enamel starts to break down, allowing the food’s natural pigments to make more persistent stains.
Tannins and chlorogenic acid are the two polyphenols, or naturally occurring plant compounds, that are responsible for staining our teeth, Bebawy says. Also found in wine and chocolate, tannins impart the drink’s pleasantly bitter flavor. Tannins and chlorogenic acid adhere to our teeth even after they’re washed away, resulting in the underlying pigment.
When coffee is roasted, the bean’s tannins and chlorogenic acid break down. Roasting the coffee longer actually increases its pH. However, they’re left more intact in light-roast coffee, which isn’t roasted for as long as dark-roast coffee. Light-roast coffee, then, has a lower, more acidic pH than dark-roast coffee, which means it can do greater damage to your chompers.
“The more that the coffee bean roasts, the more the components of the bean actually break down,” Bebawy says. “It's super counterintuitive.” In a dark roast, tannins and chlorogenic acid have deteriorated more, which means there’s less available to yellow your teeth.
Roast isn’t the only factor at play in acidity, however. Adding cow’s milk (which has a pH between 6.7 and 6.9) to your coffee also increases the pH, which makes the drink less acidic. In that case, milky coffee doesn’t stain teeth as much as black coffee. While milk doesn’t destroy tannins and chlorogenic acid the way that roasting does, it mitigates them so they’re not as potent. A 2022 paper published in the Journal of Research in Medical and Dental Science also found that adding milk or even water reduces tooth staining.
Temperature affects acid levels, too. That same paper found that “the higher the temperature of the coffee the greater the dental staining.” Bebawy says that cold brew, which is coffee brewed in cold water over several hours, is less acidic than hot coffee. In a 2018 paper published in the journal Scientific Reports, researchers made cold- and hot-brewed light-roast coffee and found that hot coffee had higher concentrations of acid. Theoretically, a cold-brewed dark-roast coffee would be even less acidic, and less prone to yellow your teeth.
Timing is everything
The time it takes for you to consume your coffee also impacts pH. Saliva has an average resting pH of 6.7, and the mouth’s resting pH doesn’t dip below 6.3. Drinking coffee temporarily changes your mouth’s pH. If you drink your daily coffee in half an hour, that change doesn’t last very long. But if you take two hours to drink a single cup of coffee, “you're presenting your teeth in your mouth with constant attack of acid,” Bebawy says. You’re not giving your saliva a chance to act as a buffer and reestablish pH levels. “So you can drink as much coffee as you want in a short amount of time to be more protected.”
She adds that it takes saliva about 20 minutes to readjust your mouth’s pH. In that time, it helps to rebuild parts of the enamel that have deteriorated from the acid. If you brush your teeth immediately after drinking coffee, then you’re just further breaking down your teeth. With that in mind, it’s best to wait 20 to 30 minutes before brushing your teeth.
The most protective coffee beverage, then, would in theory be a milky dark-roasted cold brew with lots of ice. Still, even Bebawy doesn’t let science get in the way of her morning joe. “I’m partial to light roast,” she says.
