Maybe you ve noticed it after a big run: Your sweat has a strong, cloying odor, sort of like a public restroom, perhaps. You may disregard it as an inevitable byproduct of a strenuous workout, but that ammonia smell may be a red flag your diet isn t keeping up with your energy needs. Your body normally metabolizes carbohydrates to create the fuel it requires for exercise, says Dr. William Roberts, a professor of sports and family medicine at the University of Minnesota. But if you re exercising hard and don t have enough carbs to meet your body s needs, your system will switch over to protein metabolism. MORE : When your body breaks down protein, ammonia is one of the byproducts, Roberts explains. Normally your liver would convert that ammonia into urea, a benign organic compound that your kidneys would dispel of in the form of urine.
But if you re starved of carbs and turning to protein for most of your energy, your liver may not be able to handle all the ammonia your body produces. In those instances, your sweat becomes the vehicle through which your body jettisons all of the extra ammonia in your system. You see this more in people who eat low-carb and high-protein diets, or people who are over-exercisers, like ultra marathoners, says Dr. Lewis Maharam, a New York-based physician and author of the
Running Doc s Guide to Healthy Running. Maharam says dehydration can also contribute to the smell because it makes your sweat more concentrated. If your urine is very dark yellow or brown, you re not drinking enough water, and that could be part of the reason you re smelling that ammonia. (He s quick to add that over-hydration is a more common issue among endurance athletes. ) The big takeaway here is that ammonia-scented sweat is not normal or healthy.
If you re smelling ammonia in sweat, something s wrong, Maharam says. Both he and Roberts agree you need to add more carbohydrates to your diet. Whole fruits, potatoes, rice, pasta and breads are all traditional carb sources that should help correct the problem, Roberts says. If you re engaging in super-long workouts, sport drinks and bars tend to be carb heavy, so they can help your body avoid a switch to protein synthesis, Maharam adds. If adding carbs to your diet doesn t help, see a doctor. People with liver or kidney disease also have trouble disposing of ammonia, Roberts says. It s also possible people on protein-heavy diets such as Paleo may be overburdening their systems to the point that their sweat smells like ammonia, Maharam says.
Balance is the key to health, especially when it comes to what you re eating, he adds. Going to the extreme of all protein or all fat or all carbs none of those is good for you. The Scientist: Susan Biehle-Hulette, Ph. D. , a biochemist at Procter Gamble The Answer: There are several reasons that your sweat might smell like ammonia. Most of them are nothing to worry about, but it could be a sign of something more serious. When you exercise, your body uses carbohydrates for fuel. Thatвs why you often hear about people carbo-loading before a marathon. But during long, strenuous workouts, such as marathons, or even a full-tilt day at the gym, sometimes the body needs to dip into its protein stores for added energy. When the amino acids in proteins are broken down, one of the by-products is ammonia, which is then excreted in your sweat.
Hence the stench. If you are on a low-carb, high-protein diet, you increase the chances that your body will turn to amino acids because there arenвt enough carbohydrates in your system to sustain the activity. Eating starches before a workout will give your body adequate reserves to meet your energy needs without breaking down protein. In addition, dehydration can exacerbate the problem by increasing the concentration of ammonia in your perspiration. Drinking more water while you exercise will dilute the ammonia and minimize the odor. If neither what you eat nor what you drink has any effect, you should probably get checked out by your doctor. The smell could signal an electrolyte imbalance, or damage to your liver or kidneys.