Top 8 Causes for Diarrhea

Top 8 Causes for Diarrhea

Everyone has felt what it’s like for your body to hit the eject button; you eat a delicious meal, only to find yourself with intense stomach pain in the bathroom half an hour later. So, what happened?

In most cases, diarrhea is nothing to worry about and will pass in a day or two, but it can be unpleasant until it goes away, and if it lasts for longer than this, it can be very distressing and worrisome.

Here are the 8 top reasons why you may be experiencing diarrhea:


1. Food Intolerance

Food intolerance is a common reason why people experience diarrhea. You shouldn’t discount this reason simply because you have never had a food intolerance in the past as this is something that can be developed over time if your gut health has deteriorated. When our gut health suffers, the linings in our intestines can become less discerning, and allow foods to “leak” into your system, thus causing a reaction.

If you develop a food intolerance your body is likely to respond by working to flush this food out of your system with an increased frequency of particularly soft bowel movements, represented in images 5 and 6 in the Bristol Stool Chart. Working to reduce inflammation in the gut and improving the health of your microbiome should help to improve these symptoms.


2. Food Allergy

A food allergy can also cause diarrhea and is different from a food intolerance as the body reacts with an immune response rather than simply with a chemical reaction.

When your body experiences an allergic reaction to whatever food it may be, it is going to want to get rid of whatever it is that you ate. To do this your system will work to expel it out of your body as quickly as possible, with the consequence of soft, watery, and frequent stools.

Food allergy is usually present from birth, and a reaction often comes with other severe symptoms such as rashes and breathing difficulties, so unless you’re eating something you’ve never eaten before, have a known allergy, or have other symptoms, this is the least likely reason for your diarrhea.


3. Digestive Enzyme Deficiency

Potentially the most common reason for diarrhea is a digestive enzyme deficiency, the most common of these being lactase.

Lactase is the enzyme that your body needs to properly digest dairy products. If your body is deficient in the lactase enzyme, it causes you to be lactose intolerant as you are unable to break down milk products.

Other enzyme deficiencies do exist, such as a deficiency in protease which helps break down protein, or a deficiency in cellulose which helps with the break down of fruits and vegetables.

Similar to food intolerance and food allergy, if your body lacks the right digestive enzyme to break down your food, your body will want to get rid of what you ate more quickly and the result is diarrhea. If you think you may have an enzyme deficiency, speak to your doctor or try an elimination diet, in which you eliminate the food group suspected to be causing the problem, but this is really only appropriate for a lactase enzyme deficiency – don’t eliminate protein or fruits and vegetables from your diet without the guidance of a physician.


4. Imbalanced Gut Microbiome

An imbalanced gut microbiome can also lead to diarrhea. We need bacteria in our digestive system to help maintain good gut health, but there are types of bad bacteria that can produce more hydrogen than we need, often leading to diarrhea.


Having the right gut microbiome means that our digestive systems find it easier to process food and eliminate waste in a healthier way. To find out more about how to look after your gut microbiome check out my blog series.


5. Hormone Imbalance 

Diarrhea can also be experienced as the result of a hormone imbalance, such as progesterone, estrogen, or a thyroid imbalance.

This is because hormones regulate the smooth muscle within your intestines. This smooth muscle decrees the speed at which food can move through this system. If you have lower levels of these hormones it means that food will take longer to move through your system, and if you have higher levels of these hormones it means that food will take less time to move through your system and will be softer when it is expelled.

Hormone imbalances often come with other symptoms, which vary depending on the imbalance. If you believe you may have an imbalance, you can do a blood test to have your levels checked, or speak to your doctor about your symptoms.


6. Infection

Infection is another very common cause of diarrhea. One of the most common types of infection is known as “Traveler’s diarrhea.” This comes about when you are exposed to a bug that you are not usually exposed to, typically when you are on vacation in a new country, particularly if there are substandard levels of public hygiene.

To try and get rid of this bug, or infection, your body works to increase the frequency of your stool to flush it out, usually in the form of watery and loose stools, and often soon after eating.


7. Medication Side Effect

You may find that you are having diarrhea as the result of a medication side effect. Medications that occasionally cause this include:

  • Antibiotics

  • Antacids containing magnesium

  • NSAIDs

  • SSRIs

  • Statins

  • Laxatives

Particularly with antibiotics, as they work to kill bad bacteria infecting the body, they also kill some of the good bacteria we need to keep a healthy gut microbiome which disrupts our digestive system.

Make sure that you take note of the side effects before taking any medication, and if you experience adverse symptoms, speak to your physician about the changes you’re experiencing due to the medication. Do not stop taking your medication unless advised to do so by the doctor who prescribed them to you.


8. Too Much Caffeine

A cause of diarrhea that I often see in my clinic is too much caffeine intake. We all know that caffeine does help with bowel movements and for many people, they kick off things every morning with a cup of coffee. However, as with anything, you can have too much coffee and this can have the side effect of too frequent bowel movements as the caffeine stimulates contractions that lead to movement of food through your digestive system.


If you’ve been suffering from diarrhea for a while, or it doesn’t appear to be going away, then you should make sure to contact your primary care physician or gastroenterologist as soon as possible, to make sure it is not something more serious than these reasons I have discussed above. If you are experiencing diarrhea, whether a single incident or ongoing diarrhea, make sure you increase your intake of water so you don’t become dehydrated.


Dr. Nancy Rahnama, MD, ABOM, ABIM, is a medical doctor board certified by both the American Board of Obesity Medicine and the American Board of Internal Medicine. Her specialty is Clinical Nutrition, that is, the use of nutrition by a medical doctor to diagnose and treat disease. Dr. Rahnama has helped thousands of people achieve their goals of weight loss, gut health, improved mood and sleep, and managing chronic disease.