What Supplements Can Make Your Poop Smell?

Dietary supplements are a popular option to improve health and wellness, often taken to provide additional nutrients not received from your diet.

More than half of the adult population in the United States reports taking at least one supplement in the last 30 days.

Some supplements, like chondroitin, fish oil, and iron, may lead to unwanted side effects, including smelly stool (poop).

Supplements that can make your poop smell include chondroitin, glucosamine, iron, and fat-soluble vitamins. This side effect is common with these supplements and is typically not a cause for concern.

Chondroitin and Glucosamine

Chondroitin and glucosamine are chemicals naturally found in cartilage, the supportive tissue protecting your joints and bones. In supplement form, they may help treat pain and inflammation caused by osteoarthritis, rheumatoid arthritis, and multiple sclerosis.

Chondroitin and glucosamine contain sulfate. In your intestines, bacteria help convert sulfate into sulfide gases, which cause foul-smelling odors during bowel movements and flatulence (passing gas). Hydrogen sulfide is a sulfide gas that causes a “rotten egg” smell.

Taking chondroitin or glucosamine raises the amount of sulfate and, in turn, sulfide gas in your intestines, making your poop smell.

Fish Oil

Fish oil and omega-3 fatty acids are popular supplements for conditions like inflammation and heart disease.

Fish oil supplements may cause steatorrhea, which can make poop smell fishy and appear oily. Steatorrhea is the presence of fatty oils in your stool. It occurs when your body cannot break down or digest fatty oil; in turn, the oil moves through your body, remaining in your poop.

Oil in your poop can cause it to appear pale, loose (similar to diarrhea), and smelly. The bad smell comes from fatty oil combining with other products in your gastrointestinal tract.

Garlic

Garlic is a common ingredient in many diets and dishes. It can also be taken as a supplement to treat conditions like high cholesterol, diabetes, and high blood pressure.

The characteristic smell of garlic comes from its sulfur-containing compounds like allicin, which are released when garlic tissue is cut or crushed. These sulfur and sulfide gases can also cause smelly poop. Eating garlic in your diet or as a supplement may lead to this side effect.

Iron

Iron supplements help treat and prevent anemia (low levels of red blood cells). Most prenatal multivitamins contain iron to help support the growth and development of the fetus.

Iron supplements can cause poop to have a metallic odor. Iron also commonly contains sulfide, which can give your poop a “rotten egg” smell. This is a common and expected side effect of the iron. Taking iron can also make your poop appear dark green or nearly black.

Fat-Soluble Vitamins

Vitamins are considered water- or fat-soluble based on how your body absorbs and gets rid of them. Fat-soluble vitamins, including A, D, E, and K, help with vision, immune function, and bone health. Supplements can help raise your levels of these vitamins.

Similar to other fats, your body may not fully absorb fat-soluble vitamins, causing fatty oil to be present in your poop. As with fish oil supplements, this may cause your poop to be pale and smelly.

Supplements can cause your poop to smell for many reasons, including:

• The ingredients present in the supplement
• The combination of the supplement with other medications, supplements, or foods
• A change in bacteria in your gut and intestines
• The supplement has prevented your body from absorbing nutrients properly

You may experience other gastrointestinal side effects when taking supplements that affect how your poop smells. These include:

• Dark or different-colored poop
• Constipation
• Flatulence
• Stomach bloating
• Diarrhea
• Heartburn
• Stomach pain
• Nausea or vomiting
• Smelly breath, body odor, or foul-smelling body fluids, like sweat or urine (pee)

Smelly poop can be a short-term issue, or it can be a sign of a serious health concern. If you begin experiencing any of the following signs or symptoms, talk with a healthcare provider:

• Blood in your stool or black, tarry stool
• Obvious oily-looking stool
• Pain while pooping
• Changes in the size and shape of your stool
• Changes in how often you have a bowel movement
• Fever, chills, night sweats
• Unintentional weight loss

If you begin experiencing smelly poop or similar symptoms, keep track of your symptoms. Write down any changes in your bowel movements, you poop’s appearance, the foods you have eaten, and any medications or supplements you are taking. This can be useful information for your healthcare provider.

Talk to your provider about any supplements you are taking. If you begin having any unwanted symptoms, they can help determine if the supplement is the cause and whether you should stop taking it.

If you notice smelly poop with no other serious side effects, there are treatment options you can try at home. Instead of stopping the supplement, consider the following treatments or changes:

• Dietary changes: Your diet can greatly affect how your poop smells. Avoid or reduce your intake of foods high in sulfates, like meat, seafood, broccoli, kale, dairy, alcohol, processed foods, and certain sugars. These can cause your poop to smell like rotten eggs. Food intolerances, like lactose intolerance or gluten sensitivity can also cause smelly poop.
• Drink more water: Dehydration can cause your body to absorb water from your poop, making your stool drier with a much stronger smell.
• Take a prebiotic: Restoring the healthy bacteria in your gut can help improve smelly poop. You can get probiotics through supplements or foods like yogurt, kefir, and fermented vegetables.

Dietary supplements like chondroitin, glucosamine, fish oil, and iron can cause side effects like smelly poop and other gastrointestinal symptoms.

Changing your diet, drinking more water, or taking a probiotic may also help limit these symptoms.

If you begin having unwanted symptoms like smelly poop, your healthcare provider can help you determine if the supplement is the cause and if you should stop taking it.