Bad breath is the possible side effects of following a low-carb diet such as the Atkins Diet or South Beach Diet. Sometimes it is accompanied by a bad taste in the mouth. This is known as keto-breath or ketosis breath. This can be distressing, but understanding why you have a smell of acetone or ammonia on your breath will give you reassurance that it will soon pass.
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:
- Bad breath due to acetone caused by ketosis
- An excess of protein in the diet producing ammonia in the breath.
Bad Breath from Ketosis: Keto-Breath
One of the results of cutting carbohydrates in your diet is that your body starts to use more fat for energy. This process generates molecules called ketones. One type of ketone, 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 disappears after a few weeks or a few months at the most. The reason is unclear, but it seems the body adapts 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:
- Drink more water. Try eight glasses per day to see if this helps, and then you can experiment from that point.
- Natural breath fresheners to try include mint, parsley or other greens, cloves, cinnamon, and fennel seeds.
- 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.
- Sugar-free mints or gum can be tried, but watch the carbs in them.
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 urine. In large amounts, this can smell pretty bad.
It's important to remember that you don't need lots and lots of protein in your diet. The body uses 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.
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 on a diet that is improving your health. Instead, try to figure out the cause of the bad-smelling breath and tackle it.
Ajibola OA, Smith D, Španěl P, Ferns GAA. Effects of dietary nutrients on volatile breath metabolites. Journal of Nutritional Science. 2013;2. doi:10.1017/jns.2013.26.
Anderson JC. Measuring breath acetone for monitoring fat loss: Review. Obesity. 2015;23(12):2327-2334. doi:10.1002/oby.21242.