Posted on: March 14, 2017 at 12:05 pm
Last updated: July 4, 2018 at 12:43 pm

Have you ever stopped to think before you choose garlic pizza off the menu at a restaurant? Sure, garlic tastes great, but the bad breath that stays with you is often a reason to skim to the next option on the menu.

If you’ve ever had bad breath, you’re familiar with the feeling. The one where you’re afraid someone might notice it and be repulsed.

Bad breath definitely can carry a lot of social stigmas. Which is stressful and unnecessary for many people. However, the cause of bad breath and its relation to oral bacteria and your gut health shows there’s more to know about this condition.

Bad breath may be a sign of problems in both your mouth and digestive system. As a dentist who focuses on nutrition and the mouth-body connection – bad breath is a warning sign of you may have problems with our microbiome.  

The different causes of bad breath

Transient bad breath is the type that is caused by certain types of food. Certain foods (like garlic) are broken down into volatile sulphur compounds (VSCs) known for their smell.When you eat these foods that compound that break down into VSCs, your breath will smell until they clear your system.

But what about non-transient bad breath?


Research shows that 90% of more permanent bad breath is due to problems in the mouth. These may be tooth decay or failed dental work. Most commonly bad breath is related to gum disease and builds up on the top, back part of the tongue.

However, it can also be caused by systemic issues. Nasal infections, digestive problems or more serious conditions like liver failure can also cause bad breath.

Why mouthwash won’t help your bad breath

In the dental practice, we probably come across more bad breath than the average person. When I see patients who suffer from chronic bad breath, there are some tell-tale signs. They often don’t want to open their mouth for a dental exam. They also often use mints and or gum – a lot. Or worse even they use mouthwash. The problem with using mouthwash to hide bad breath is just that – it only hides the problem.

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Scientists aren’t really sure how the ingredients in mouthwash work to kill bacteria in the mouth and body. Alcohol, for example, is known to have antibacterial properties. But studies have shown it to be not very effective on the bugs that commonly cause bad breath. These are nasty types of bugs that turn chemicals in your mouth to smelly VSCs.

Bad breath is a loss of your good bacteria

Your mouth and oral microbiome house over 600 species of bacteria. So far, only a fraction of these bugs is known.

We know that dental diseases are caused by bad species of bacteria. But certain species are known to play a protective role in the mouth. That is, they stop bad bacteria from overgrowing by acting as a ‘bodyguard.’

And here’s why we should pay attention to our oral bacteria. They play a key role in managing not only your oral health, but also your gut health. Simply knocking bacteria out with mouthwash doesn’t fix the problem.

The mouth-gut connection.

Bacteria that live in your mouth don’t simply stay there. Every time you swallow, you send thousands of microbes from your mouth to your digestive system.


Your gut bacteria are the biggest population in the human microbiome. They are also responsible for digestion, metabolism, your immune system, and even the brain.

Many species of bacteria in the gut are known to manage many processes in your body. Bad breath that begins with the oral microbiome eventually travels to your gut. It’s also likely how our gut bacteria get there in the first place. The mouth acts as kind of a ‘vetting’ or passport system that checks which bugs are allowed into your gut.  

Bad breath and the microbiome.

As a dentist, I always try to find the cause of diseases I see in the mouth. Many conditions in the mouth are often signs of problems all over the body.

Transient bad breath can be stopped by avoiding foods that break directly down into VSCs like garlic and onions. But if your bad breath is more persistent (or non-garlic pizza related) then it’s likely an imbalance in your oral microbiome.


Bad breath in these cases is caused when harmful bacteria make compounds like VSCs. But the potential to cause gut imbalance and other issues mean that it’s time to stop being embarrassed about bad breath.

How to Address Chronic Bad Breath

If you have bad breath and removing these foods doesn’t help, you should talk to your dentist today. In addition, try taking some of these steps to address your gut health: 

  • increase your intake of probiotics and fermented foods like kimchi, kefir, and yogurt
  • eat more high-fiber foods like beans, lentils, broccoli, and avocados
  • talk to your nutritionist or medical care provider to identify any potential gut irritants in your diet
  • cut down your intake of processed foods and sugar (including drinks!) and replace with whole foods as much as possible

In the meantime, chewing on parsley can be a better, more natural short-term alternative to chewing gum or mints.

For more information on how your mouth connects to your body and how nutrition affects your mouth visit and sign up to my email series.

Disclaimer: This information is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your dentist or other qualified health provider with any questions about your oral health, medical condition and/or current medication. Do not disregard professional medical advice or delay seeking advice or treatment because of something you have read here.

Dr. Steven Lin is currently the Principal Dentist at Luminous Dentistry, a dental practice on the Central Coast of New South Wales, Australia, that strives to give individuals of all ages the best possible smile.

Dr. Steven Lin
Board Registered Dentist
Dr Steven Lin is a practicing board accredited dentist, writer and speaker. As passionate health educator, Dr Lin works to merge the fields of dental and nutritional science to show how the mouth is an integral part of our overall health. As a TEDx speaker his work has been featured on influential health websites such as MindBodyGreen and Dr Lin is now working on his own publication ‘The Dental Diet’ an exploration of how food is the foundation of oral health.

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