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Everything you wanted to know about stools but were too afraid to ask


Unusual bowel and bladder actions we may have ignored when younger can now be harbingers of more serious health symptoms in senior years …. and shouldn’t be dismissed.

The colour of your stool can tell you a lot about your diet and your health.

Did you know the medications you take also change the colour? For example, iron supplements and anitidiarrheal medications can turn the stool black.

Normal stools are usually brown to green but black or bloody can mean something more serious.

Black can suggest bleeding in the upper gastrointestinal tract and maroon coloured or bloody stools suggest bleeding in the lower GI tract. Best to see your GP.

The good, the bad and the bloody


Did you know the brown colour of stools initially comes from the red of blood?

Dr Vincent Ho is a Senior Lecturer and clinical academic gastroenterologist at Western Sydney University and his research has been published in The Conversation.

Haemoglobin is the red protein in blood that transports oxygen around the body. It’s eventually broken down into a substance called bilirubin.

In the liver, bilirubin is used to form bile and is released into the small bowel to help digest food. Bile then passes into the colon and the bilirubin is broken down by bacteria.

The final stage in the process is the addition of a substance called stercobilin, which gives the stool its brown colour. All shades of brown are considered normal.

What if it’s green?


According to Dr Ho, it would seem there’s not too much to worry about.

Green stools contain significantly more bile acids than brown stools. If food is moving through the bowel very quickly – if you have diarrhoea, for instance – there isn’t enough time for the green bile to break down completely, giving stools a green colour. Green leafy vegetables can also cause this.

That applies to other coloured stools as well:

  • Blue – typically caused by food dyes and food additives that are unable to be completely broken down in the gut. Blueberries too!
  • Orange - can be due to beta carotene, a compound found in carrots and butternut pumpkin. Stools can also be orange because of antacids containing aluminium hydroxide, a naturally occurring salt.
  • Yellow - is often normal but a greasy, foul-smelling yellow stool that floats on the toilet water can mean an excess of fat. Occasionally, this can arise from conditions such as undiagnosed coeliac disease, where the immune system reacts abnormally to gluten and the small bowel doesn’t properly absorb fat.
  • Pale, cream or clay-coloured - can indicate a blockage of bile from the liver to the small intestine. This means it doesn’t go through the last stage of getting its brown colour, through the addition of stercobilin. This results in the stool having a very distinct pale cream appearance.

Should I be worried?


Dr Ho says changes to the colour are usually temporary. Finishing the medication or removing the responsible food from the diet should return stool colour to its normal shade of brown. But if the odd colour persists, it may signify an underlying medical condition and warrant further investigation.

Key takeaway: Black, red and very pale stools are the more concerning colours and should be checked out by your GP.


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