You could say that the human body is a creature of habit. Whenever homeostasis is threatened, your system can get temporarily thrown out of whack. A major change in your diet, such as severely restricting carbs, can cause a host of ketosis symptoms, including suspicious-smelling urine.
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Reducing your carb intake to very low levels can cause your body to produce ketones, which may give the urine an unappealing odor.
Low-Carb Diets Explained
"Low-carb diet" is a very broad term that encompasses different dietary patterns, but all focusing on the intake of fewer carbs than the recommended adequate intake (AI) of 130 grams a day, which is the fewest amount of carbs your body needs to support health and prevent nutrient deficiencies, according to the Institute of Medicine. That's a wide spectrum. A low-carb diet could include 100 grams of carbs per day, or it could include much less.
A moderate, low-carb diet shouldn't cause any major side effects — maybe some fatigue and weakness. It's the very low-carb diets, such as the popular ketogenic diet, that are more likely to cause marked symptoms, such as more intense fatigue, nausea and constipation. You may also experience:
Bad breath is another common symptom of very low-carb diets. The odor is often described as "fruity," but not in a good way. Although not as common, your sweat and urine may have a similar odor.
Ketosis Urine Odor
When you severely restrict carbs, your body is deprived of its main source of energy, and it has to find an alternate source. This facilitates a natural metabolic process called ketosis, in which the body breaks down fatty acids to produce substances called ketones, which can be used for energy.
There are three types of ketone bodies present in the blood in ketosis — acetoacetate, β-hydroxybutyrate and acetone, the last of which is responsible for the fruity odor. People often describe the odor as smelling like nail polish remover, which often contains acetone as a solvent.
The higher the concentration of ketone bodies in the blood, the more pungent the smell is likely to be. In people with diabetes especially those with Type 1 diabetes, a fruity odor to the breath can be a sign of a serious condition called ketoacidosis, in which ketones build up to dangerous levels.
Nutritional ketosis and diabetic ketoacidosis are not the same thing. According to an article published in October 2015 in the Journal of Medical Case Reports, non-diabetic ketoacidosis occurs very rarely, and is usually due to starvation or alcoholism. A healthy, low-carbohydrate diet should not cause ketoacidosis.
Getting Rid of the Odor
The easiest way to fix the keto urine smell is to add more carbs back into your diet and get out of ketosis. But if you're committed to a keto lifestyle and you're going to stick it out, there may be a few tweaks you can make to your diet to reduce the odor:
Reduce your protein intake: If you get your macros wrong and eat too much protein, it can make the smell worse. This is because your body produces ammonia during the breakdown of protein, according to the Clinical Journal of the American Society of Nephrology in August 2015. Ammonia combined with acetone makes for some particularly strong breath and urine.
According to registered dietitian Sherrie Sonomura, the keto diet typically contains 20 percent protein. It is not a high-protein diet, but people often eat more protein than they should and not enough fat. Do some math and make sure you're getting enough, but not too much.
Stay hydrated: Diets, in general, can cause a lot of water loss, especially in the beginning; but low-carb diets can be especially dehydrating. You can tell when you're dehydrated by looking at the color of your urine — when properly hydrated, urine should be a light straw color; when dehydrated, the urine is dark yellow or brown. It may also have a stronger smell because it's more concentrated.
On a keto diet, drinking water and other unsweetened beverages should be like a second job. If you get dehydrated, in addition to foul-smelling urine, you may also feel tired and dizzy — even more than usual when starting a keto diet. If you're also having problems with smelly breath, the dry mouth that dehydration causes can make the problem worse.
You probably need to drink more than you think. According to the Mayo Clinic, women need 11.5 cups of fluids a day, and men should drink 15.5 cups of fluids per day. Some of that comes from your diet, but the lion's share should come from that water bottle you keep by your side every waking minute.
Other Reasons for Urine Odor
If your urine doesn't have the characteristic keto urine smell, and your breath doesn't also smell, you may want to consider other reasons for your odoriferous pee. Even in the absence of ketones, being dehydrated can lead to smelly urine, so be sure to drink up. Certain foods and beverages can make urine smell more pungent, including asparagus, coffee and tea. Vitamins and medications can also lead to a more distinct urine smell.
A change in urine odor can be caused by some medical conditions, which may require a visit to your doctor, such as:
- Urinary tract infection
- Bladder infection
- Bladder fistula
- Liver failure
Also keep in mind that, although the unpleasant, fruity odor is normal on a keto diet, it can also be an early indication of diabetes, reports the Mayo Clinic. Other warning signs include:
- Excessive thirst
- Frequent urination
- Nausea and vomiting
- Abdominal pain
- Weakness or fatigue
- Shortness of breath
These symptoms are similar to some of the nutritional ketosis side effects, which can make detecting diabetes problematic. This is why it's always a good idea to consult with your doctor before starting a keto diet.
A very low-carb diet can be helpful for managing blood sugar in both Type 1 and Type 2 diabetes, according to several recent studies, including one published in Pediatrics in June 2018 and another published in the Journal of Medical Internet Research in February 2017. However, it should be undertaken only with your doctor's instructions and frequent monitoring.
- National Academies of Medicine: "Dietary Reference Intakes: Macronutrients"
- Mayo Clinic: "Low-Carb Diet: Can It Help You Lose Weight?"
- StatPearls: "Ketogenic Diet"
- ScienceDirect: "3 Hydroxybutyric Acid"
- Mayo Clinic: "Diabetic Ketoacidosis"
- Journal of Medical Case Reports: "Ketoacidosis Associated With Low-Carbohydrate Diet in a Non-Diabetic Lactating Woman: A Case Report"
- Clinical Journal of the American Society of Nephrology: "Urea and Ammonia Metabolism and the Control of Renal Nitrogen Excretion"
- National Kidney Foundation: "To Keto or Not to Keto?"
- StatPearls: "Low Carbohydrate Diet"
- MedlinePlus: "Dehydration"
- MayoClinic: "Water: How Much Should You Drink Every Day?"
- Metabolites: "Quantitative Determination of Common Urinary Odorants and Their Glucuronide Conjugates in Human Urine"
- MedlinePlus: "Urine Odor"
- AARP: "What's That Smell? Possibly a Health Issue"
- Pediatrics: "Management of Type 1 Diabetes With a Very Low–Carbohydrate Diet"
- Journal of Medical Internet Research: "An Online Intervention Comparing a Very Low-Carbohydrate Ketogenic Diet and Lifestyle Recommendations Versus a Plate Method Diet in Overweight Individuals With Type 2 Diabetes: A Randomized Controlled Trial"