These are only some possible causes for changes in stool colour, but not always the reason. Always think about what you ate the day before.
-If it's very dark brown or black, check for blood. This may be visible or microscopic and may need to be checked out by a lab. This could indicate gastrointestinal blood loss from a bleeding ulcer, a lesion such as bowel cancer, gastritis (may be from steroidal use), diverticulitis, ulcerative colitis, long distance running (this is from excessive running though) and many more reasons. Or may be as simple as eating alot of beetroot.
- Black tarry stools may indicate too much iron intake or eating liqorice.
- Obvious blood and pus can indicate infection either by parasite; bacteria etc, but can also be an inflammatory disease such as Cohn’s disease or another inflammatory process of the bowel like colitis and the reason listed above. Blood upon wiping could indicate piles/haemorrhoids?
- Yellow stools can indicate liver and/or gall inflammation or blockage or pancreatic dysfunction. Can be from a congested liver, gall stones. Can also be a viral illness such as hepatitis.
- Obstruction of bile ducts when complete then stools are off-white or grey and no urobilinogen can be formed, so urobilinogen is absent from the urine.
-Floating stools may indicate that fats are not being properly broken down by the liver and gall bladder. But can also be due to intolerance to gluten. Some people have floating stools because of psyllium intake.
-If you have particularly greasy, smelly, floating stools, you may have a problem absorbing fat from your gut. The problem may be in your pancreas or small bowel.
-Lactose intolerance- frequent explosive watery stools which may be yellow or green, depending on severity.
-If your stool comes out in a long thin string despite a normal appetite and normal eating patterns, you could have a parasitic infection (worms).
-Usually pale stools indicate Giardia and black stools hookworm. This is not a steadfast rule though.
-If you are detoxing or fasting then your bowel motions will most probably be different as your body is excreting the toxins through the bowel. As already mentioned they may turn yellow or be lighter/darker as your liver is trying to deal with the extra strain of detoxing. This shouldn’t last for very long and you will probably notice that your urine is different as well.
- Green stool -eating green foods. Green, leafy vegetables contain chlorophyll which could be colouring the stool green. Iron supplements or even foods rich in iron can also give stool a green tinge or eating a lot of liquorice. The stool can also appear green for physical reasons, and not just what you've been eating. Bile that is secreted in the first part of the small intestine is actually green. As stool is digested and passed through the large intestine it is turned into a darker brown colour. Also could mean that it went through the large intestine too fast to be changed in colour. This is often called "rapid transit" or "decreased colonic transit time" and diarrhoea that is green in colour could be the result.
If there are changes in your stool that you cannot attribute to something that you are doing in your diet, then be sensible about it- tell your Dr! The point is, you can't diagnose yourself, and more serious causes must be ruled out.