Understanding Stool Color Changes: When to Worry and When Not To

As we mentioned above, green stools are actually quite common. But when it turns from brown to completely green, the following things can cause it -

• Green vegetables, such as spinach or kale
• Green food colouring, such as beverages or ice pops
• Iron supplements

If you are having green diarrhoea, the colour may not be due to your food, the likely reason is that your food passes through the large intestine too quickly and if the stool passes through the intestine too quickly, there is not enough time for the bile to be digested and broken down to give the stool its normal brown colour.

Normally, bacteria found in the intestine chemically change the bile from green to brown. It takes time for the bile to completely change colour in the intestine and then it becomes brown or grey and if the transit time is short i.e. it passes quickly, for example, when a person has diarrhea, the stool remains green in colour.

(Read more - How to Treat Blood in Stool at Home Safely)

Bright red stool can be caused by beetroot, cranberry, tomato juice or soup, red coloured foods such as red grapes or other beverages, gelatin, ice pops, red candy and red frosting. Red medicines such as amoxicillin can also cause red stool.

If you don't think your diet is the cause, the reason for your red stool could be blood. If the colour of the stool is bright red, the blood is coming from the lower part of your digestive system. The common causes can be as follows -

The most common causes of red stool in adults are bleeding due to hemorrhoids, noncancerous tumors, inflammation of the intestines called colitis, discomfort caused by small pouches in the lining of the colon called diverticular disease. 

In babies, the most common cause of red stool is a cut or tear in the tissue around the anus. If you are having red stool that is not caused by the food you ate, get it checked by your doctor.

Babies have black stool for the first few days after birth. After that, it could be because they have eaten some very dark colored food or taken a medicine or supplement that causes black stool. Black stools are a worrisome symptom, as they can be caused by large amounts of bleeding in the gastrointestinal tract, often in the upper gastrointestinal tract (esophagus, stomach, and duodenum). Some foods, medications, and supplements that can cause black stools include:

• Bismuth subsalicylate (Kaopectate, Pepto-Bismol)
• Black licorice
• Iron supplements
• Blueberries, etc.

Stool that looks like tar can often be a sign of bleeding in the digestive tract. Some of the causes include -

• A bleeding sore in your esophagus from acid reflux
• Non-cancerous tumors
• Ulcers 
• Cancer etc. 

If you think the black stool is not due to what you ate, you need to talk to your doctor.

(Read more - How to Relieve Constipation Fast: Tips and Tricks)

Medicines given for diarrhea, such as bismuth subsalicylate (Kaopectate, Pepto-Bismol), can sometimes cause pale or clay-gray stools. Barium, a chalky liquid that is given to you before an X-ray of the upper part of your digestive system, can also cause white stools. 

White or clay-colored stool may be due to a lack of bile, which can result from a blockage in the bile ducts. Gallstones are a possible cause of such a blockage. It can also be caused by pancreatic cancer that blocks the bile ducts. Liver disease, such as hepatitis, can prevent bile from getting to your body's waste.

Yellow stool may mean you've been eating foods high in yellow coloring, such as sweet potatoes, carrots or turmeric.

If the onset is recent, yellow stool may also be a sign of an intestinal infection, especially if there is diarrhea, fever, flu-like symptoms and abdominal cramps. Giardiasis, an infection of the small intestine caused by the parasite Giardia lamblia, can cause yellow stool or diarrhea.

(Read more - How to Manage and Treat Bleeding Piles)

Also, people with gastroesophageal reflux disease (GERD) and those taking medication for GERD may sometimes have yellow stools.

This shade can also be normal for many people. It is common for babies, especially those who are breastfed. But if you are having yellow stools that look greasy and smell very bad, it may contain too much fat. This can be a sign that your body is not digesting food properly.

(Read more - Stool Culture Test)