When it comes to bowel movements, we all know they’re not going to smell like roses! It’s normal to have an unpleasant smell, given it’s one of our body’s ways of expelling waste.

That being said, sometimes stool can smell worse than usual and it might last for a few days or weeks at a time, which could indicate some health issues. Alternatively, the change in scent may be caused by particular foods that are known for temporarily making your stool smell worse than normal.

Keep on reading to find out why your stool may have a different odour than usual, plus learn a few tips to help maintain your gastrointestinal (gut) health.

Now we mentioned earlier that poo is one of our body’s ways of excreting waste - which comes from the food we consume. But it’s also made up of a lot more than just food!

As food moves through our digestive system, it reaches our small intestines where most of the nutrient absorption and digestion happens. The remaining material then goes into our large intestine, where good bacteria and microorganisms get to work breaking it down into usable nutrients through partial fermentation [1]. The final stop on the journey is the rectum, which stores the solid faecal matter and absorbs excess water until a nerve signals that you need to ‘go’.

So, faeces are made up of a lot of different things as well as indigestible food! There’s also water, fats and dead microorganisms contained in stool.

If you’ve noticed a drastic change to the smell of your stool (that’s temporary only), it may have been caused by certain foods. These foods can include:

• Cruciferous Vegetables
  

  This diverse group of green vegetables are full of nutrients like vitamins C, E and K, folate, minerals and fibre. But, they also have sulphur-containing chemicals that contribute to their pungent smell - which has the same effect on your poo [2]!

  While eating these vegetables is undoubtedly beneficial to your diet, reducing the amount you consume might help to avoid foul-smelling stools. Cruciferous veggies include:

  • Broccoli

  • Cauliflower

  • Cabbage

  • Kale

  • Brussel sprouts

  • Bok Choy

  • Radish

• Sulphur-Rich Foods
  

  It's not just cruciferous vegetables that are high in sulphur compounds that worsen the smell of your stool! You'll also find sulphur in:

  • Allium vegetables like garlic, onion, chives and leek

  • Dairy products including milk, yoghurt, mature/aged cheeses

  • Certain legumes such as kidney beans, black beans and soybeans

  • Meat, particularly beef, ham and chicken

  • Fish and seafood including scallops, mussels and prawns

  It's important to remember that sulphur is a crucial element that our bodies need to function properly [3], so instead of cutting them out completely, try to limit or reduce intake.
  
  

• High-Fat Foods
  

  Eating a lot of fatty foods can overwhelm your digestive system - making it unable to break down all of the fat, and therefore the body can’t absorb it. When this happens, the fat gets to the colon and rectum in an undigested state - resulting in foul-smelling, oily and pale-coloured diarrhoea (also called steatorrhea).

  However, steatorrhea can also be caused by several health conditions, like coeliac disease or pancreatitis. If you find you're often having smelly, oily stools, we recommend checking in with your doctor.
  
  
• Alcohol
  Excessive consumption of alcohol can often result in an unpleasant trip to the bathroom the day after. Alcohol can irritate the lining of the bowel, which can lead to smelly, loose stools - and if your alcoholic beverage is mixed with a sugary drink, this effect can be worse.

Some medications can cause your stool to smell worse for a short time while you take them, such as antibiotics.

Since antibiotics take a ‘scatter-gun’ approach to killing bacteria, they can disrupt digestive function by throwing off the balance of good bacteria in the digestive tract, resulting in stinky and loose stools. Incorporating a probiotic supplement, or probiotic-rich foods into your diet following a course of antibiotics can help to rebuild your good gut bacteria [4].

Remember, always speak to your doctor before making any changes to your diet or supplement regime.

If having foul-smelling stool is more of a consistent issue rather than a temporary ‘one-off’, it could indicate a more serious health issue.

This could include:

• Food Allergy or Intolerance
  

  If you have a food allergy or food intolerance, such as lactose intolerance for example, you might notice you experience bloating, nausea, abdominal pain or cramps, along with flatulence and bad-smelling stool/diarrhoea after consuming the food you’re allergic to.

  If you suspect the worsened smell of your stool could be due to a food allergy or intolerance, it's a good idea to see a doctor about it and keep a food and bowel diary to track if your symptoms could related to specific foods.

   

• Infection or Illness
  Many viral, bacterial and parasitic infections can cause foul-smelling faeces. This includes salmonella bacteria, which is one of the most common causes of food poisoning [5].
  
  Contracting an infection or illness from consuming food contaminated with certain viruses, bacteria or parasites can not only cause your bowel movements to be more frequent, smellier and looser than usual but usually comes with the added symptoms of abdominal pain, cramping, vomiting and even a fever or chills.
  
  If you’re experiencing these symptoms, it’s best to get checked out by a doctor as prolonged bouts of diarrhoea and vomiting can cause dehydration.

• Inflammatory Bowel Disease (IBD)
  

  Crohn’s disease and ulcerative colitis are two conditions that fall under the inflammatory bowel disease (IBD) umbrella, and both are characterised by chronic inflammation of the gastrointestinal tract [6].

  While the two conditions are different, they have similar symptoms, including unpleasant-smelling stool and chronic diarrhoea.

  These conditions are long-term as unfortunately, they don’t currently have a cure - but once diagnosed, they can be effectively managed with different treatment options. If you suspect you may have an inflammatory bowel disease, it’s important to seek a diagnosis from medical professionals.

There are many things you can do to ensure the health and optimal functioning of your gastrointestinal system, which can also help reduce the odour of your bowel movements:

• Eat a healthy, varied diet with limited intake of processed or high-fat foods

• Eating less foods that are high in sulphur content

• Limiting alcohol consumption

• Avoiding any foods you’re allergic to or have noticed trigger any upset

• Ensure you’re drinking enough water to combat any potential constipation