Alan Frischer, MD, MPH
My wife will not eat asparagus. She’s well aware that it’s a highly nutritious dark green vegetable, but has never liked the flavor. That has spared her from experiencing one of the more famous qualities of this particular vegetable: asparagus makes the urine smell terrible!
Patients frequently ask me why their urine smells bad. Here are a few of the most common causes:
The wide variety of foods that can result in smelly urine is surprising. Among them are onions, Brussels sprouts, garlic, bananas, turkey, chicken, salmon, curry, many spices, and even some types of coffee. In the case of asparagus, scientists suggest that asparagusic acid is converted to a sulfa-containing chemical…that smells.
Overall, the most common reason that urine starts to smell is not due to the food we consume, but to dehydration. It’s easy to know if we are dehydrated by our urine’s dark color. The quick and easy cure? Drink more water.
For women, urinary tract infections are the most common cause of smelly urine. The smell may be ammonia-like, or foul, or even slightly sweet. The same bacteria that cause the UTI cause the odor.
A yeast infection in the vagina may lead to a yeasty urine smell. Although the infection is inside the vagina, the urine picks up the smell as it passes through the urethra.
Diabetes can change the odor of urine. Diabetics often need to urinate more frequently, depending on how well controlled the blood sugar is. When sugar is in the urine, it results in a sweet, fruity smell. (The sweet taste of urine was long used as a diagnostic tool for diabetes!)
Cleaning by douching is no longer commonly done, and I don’t recommend it. It changes the microbiome and the pH balance, and can lead to smelly urine.
Due to chemical and hormonal changes, pregnancy can lead to a change in the smell of the urine. It becomes more pungent, and is strongest during the first trimester.
Some sexually transmitted diseases, especially chlamydia, can cause an odor in urine.
Certain medications can cause urine to smell, including a number of antibiotics. Some vitamins, including the B vitamins, concentrate in the urine and change both the color and smell.
Any unexplained change should trigger a visit to your physician. Most of the causes of smelly urine can and should be promptly treated.