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Is Your Low-Carb Diet Giving You Bad Breath?

Solutions for Bad Breath from Ketosis and Related Causes

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Updated May 29, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Is Your Low-Carb Diet Giving You Bad Breath?
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One the possible "side-effects" of following a low-carb diet (be it Atkins, South Beach, or any other low-carb diet plan) is "bad breath", sometimes accompanied by a bad taste in the mouth. This is distressing, of course, but don't think you're condemned to live with it!

What causes bad breath on a low-carb diet?

There are many causes of bad breath, but if the change in your breath happened suddenly after starting a low-carb diet there are two main causes: 1) bad breath due to acetone caused by ketosis, and 2) an excess of protein in the diet producing ammonia in the breath.

1. Bad Breath from Ketosis ("Keto-Breath")

One of the results of cutting carbohydrates in our bodies that is that we start to use more fat for energy. This process generates molecules called "ketones". One type of ketone, called acetone, tends to be excreted, both in the urine and the breath. The description of the smell varies, but it is often described as "fruity" or like the smell of apples which are "past their prime" (or even downright rotten).

The good news is that keto-breath usually doesn't last forever. Most people find it dies down after a few weeks, or at the most a few months. The reason is unclear, but it seems our bodies adapt in some way. Children on a ketogenic diet for epilepsy have been shown to have less acetone in their breath as time goes on, for example. In the meantime, there are things you can do to minimize the impact of "keto-breath":
  1. Drink more water: try 8 glasses per day to see if this helps, and then you can experiment from that point.
  2. Natural breath fresheners to try include mint, parsley or other greens, cloves, cinnamon, and fennel seeds.
  3. Some people swear by breath capsules, which are usually made from parsley oil (e.g. Mint Assure) for keto-breath. Others find they do not help.
  4. Sugar-free mints or gum can be tried, but watch the carbs in them.

2. "Ammonia Breath" from Protein

When the body metabolizes protein, ammonia is produced. When people eat high-protein meals, there tends to be increased ammonia in their breath and/or urine. In large amounts, this can smell pretty bad.

It's important to remember that we don't need lots and lots of protein in our diets. Our bodies use protein to maintain and build muscles, to make enzymes, and for other structural and chemical needs. The body will convert excess protein to energy, which is where you will get the extra ammonia (this also happens during starvation or long exercise when the body begins to rely on breaking down muscles for energy if it runs out of sources of fats and/or carbohydrates).

Find Out How Much Protein Your Body Needs

Sometimes people load up on protein because they are afraid to eat more fat. This is one of the reasons why it is rarely a good idea to try to eat a diet that is low in both carbohydrates and fats. The solution to "ammonia breath" for people on a low-carb diet is often to increase fats in the diet, and cut back some on protein foods.

Above all, don't let problems with your breath derail you from staying with a diet that is improving your health. Instead, try to figure out the cause of the bad-smelling breath and tackle it.

Sources:

Musa-Veloso K, Rarama E, et al "Epilepsy and the ketogenic diet: assessment of ketosis in children using breath acetone." Pediatric Research 52(3):(2002)

Musa-Veloso K, Likhodii, S, et al. "Breath acetone is a reliable indicator of ketosis in adults consuming ketogenic meals." American Journal of Clinical Nutrition, 76(1): (2002)

Smith David, et al. "Trace gases in breath of healthy volunteers when fasting and after a protein-calorie meal: a preliminary study." Journal of Applied Physiology, 87(5):(1999)
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