Why does keto cause bad breath? A guide for dental professionals

The ketogenic diet-colloquially known as the "keto" diet-involves consuming high amounts of fat and very minimal carbohydrates in order to lose weight. Eschewing carbs puts the body into a state of ketosis, which causes it to use ketones as a source of energy as opposed to glucose (which we as humans naturally run on).¹ Ketones are water-soluble molecules produced by the liver to act as an "emergency" fuel source when the body does not have enough glucose.¹

What is "keto breath?"

Ketosis drastically reduces blood sugar and insulin levels, which helps burn fat quickly and efficiently. Those following the keto diet primarily consume eggs, nuts, fish, meat, and natural oils and tend to avoid carb-heavy foods such as grains, alcohol, and baked goods.¹

Although many have found success following this fad diet, common side effects include kidney stones, extra fat in the liver, nutrient deficiencies, and bad breath.¹

Keto breath vs. perio breath

Bad breath caused by the keto diet is different than halitosis due to poor oral hygiene or other issues-it has a distinct odor produced from the extra ketones in the saliva. But how can dentists and hygienists tell the difference between "keto breath" and something else?

After all, bad breath can manifest for several different reasons and be a side effect of other common oral health conditions like tonsil stones and halitosis. If you encounter a patient with particularly bad breath, it's important to identify the underlying cause.

If tonsil stones are the culprit, you'll be able to tell right away; also known as tonsilloliths, these tiny white stones lodge themselves in the crypts of a patient's tonsils. They are formed when trapped debris from food calcifies over time.²

"Perio breath" is different. Unlike "keto breath," the bacteria associated with periodontal disease produce volatile sulfur compounds (VSCs). These compounds can produce a foul odor that typically smells like decay or rotten eggs. VSCs result from oral bacteria breaking down food particles in the absence of sufficient oral hygiene.³Keto breath, on the other hand, reminds many people of acetone and is often accompanied by a fruity taste in the mouth.

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Ways to eliminate odor

Keto breath typically manifests a week into the diet and will go away with time. However, there are still some ways to get rid of or lessen the pungency of their bad breath. If you encounter a patient suffering from keto breath, try offering them the following tips:

Eat more carbs. This may seem like a contradictory piece of advice, but consuming only five additional grams of carbohydrates per day can make a huge difference. Keep in mind that most keto dieters only have roughly 20 to 50 grams daily.¹

Drink more water. Ketones exit the body through urination, so staying hydrated will help flush them out faster.

Limit protein intake. Eating an abundance of protein at the beginning of the keto diet can actually make bad breath worse. It may be helpful to consume meat-free options like avocados, almonds, and plant-based oils to keep fat content high.

Brush more frequently. It goes without saying that brushing removes plaque and food particles from the mouth. Sugar-free gum and mints may also be helpful for patients with bad breath.⁴

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