Why Does Coffee Make Your Breath Stink? The Science Behind the Unpleasant Odor

Coffee is one of the most popular beverages in the world, enjoyed by millions of people every day. Its rich and invigorating aroma can wake us up and keep us going throughout the day. However, there is one downside to drinking coffee that many people are familiar with – the dreaded coffee breath. Have you ever wondered why coffee can leave such a strong and unpleasant odor in your mouth? In this article, we will delve into the science behind this phenomenon and explore the factors that contribute to coffee breath.

Coffee Breath and Volatile Sulfur Compounds

The Culprit: Volatile Sulfur Compounds

To understand why coffee can make your breath stink, we need to first examine the composition of coffee itself. Coffee contains several compounds that contribute to its aroma and taste, including volatile sulfur compounds. These compounds are responsible for the distinctive smell of coffee and can also leave a lasting odor in your mouth.

What are Volatile Sulfur Compounds?

Volatile sulfur compounds (VSCs) are a group of chemical substances that are known for their pungent smell. They are produced during the brewing process as the coffee beans are roasted, and they can also be found in other foods like onions and garlic. These compounds are highly volatile, meaning that they easily evaporate and can be detected by our nose even at extremely low concentrations.

The Role of Bacteria in Coffee Breath

While volatile sulfur compounds are present in coffee, they do not directly cause bad breath. The unpleasant odor actually arises when these compounds interact with the bacteria that naturally reside in our mouths. Our oral cavity is a complex ecosystem, home to millions of microorganisms, including bacteria. Some of these bacteria can break down the volatile sulfur compounds found in coffee, producing other compounds that have a foul smell.

Factors Contributing to Coffee Breath

Coffee’s Effect on Saliva Production

One of the primary factors that contribute to coffee breath is the reduction in saliva production caused by coffee consumption. Saliva plays a crucial role in maintaining oral hygiene by washing away food particles and bacteria. When saliva production decreases, the bacteria in our mouths can multiply, leading to an increase in odor-causing compounds.

Acidity of Coffee

Another factor that can worsen coffee breath is the acidity of coffee. Coffee is naturally acidic, and this acidity can affect the pH balance in our mouths. When the pH level becomes imbalanced, it provides an ideal environment for the growth of odor-causing bacteria.

Drying Effect of Coffee

Coffee also has a dehydrating effect on our bodies. When we consume coffee, it acts as a diuretic, meaning it increases the production of urine and can lead to dehydration. Inadequate hydration can contribute to dry mouth, which in turn can exacerbate bad breath.

Preventing and Treating Coffee Breath

Maintaining Good Oral Hygiene

To combat coffee breath, it is essential to maintain good oral hygiene. This includes regular brushing and flossing, along with using mouthwash to rinse away bacteria and food particles. Additionally, consider investing in a tongue scraper, as bacteria can accumulate on the tongue and contribute to bad breath.

Drinking Water

To counteract the drying effect of coffee, make sure to drink plenty of water throughout the day. Staying hydrated will help promote saliva production and reduce the likelihood of dry mouth.

Avoiding Strong Flavors and Ingredients

Certain foods and drinks can exacerbate bad breath, so it is advisable to avoid them when trying to combat coffee breath. Foods like onions and garlic, which also contain volatile sulfur compounds, can contribute to the buildup of unpleasant odor. Similarly, alcoholic beverages and smoking should be avoided, as they can further dry out the mouth and worsen bad breath.


While coffee is undoubtedly a beloved beverage, it can leave an unpleasant odor in your mouth. The volatile sulfur compounds present in coffee, along with the interactions with bacteria in our mouths and the drying effect caused by coffee consumption, all contribute to coffee breath. By maintaining proper oral hygiene, staying hydrated, and avoiding strong flavors and ingredients, you can mitigate the effects of coffee breath. So, enjoy your cup of joe, but be mindful of the steps you can take to combat the odor it may leave behind.

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