Can Probiotics Cause Diarrhea?

Probiotics have garnered significant attention in recent years for their potential benefits for gut health, becoming a common addition to yogurt, fermented foods, and dietary supplements. However, there's also ongoing debate about whether probiotics can cause diarrhea. Some people experience diarrhea after taking them, while others find them effective in alleviating the condition. So, are they a cause or a solution to diarrhea? Let's learn more.

1. What are probiotics?
Probiotics are "live microorganisms which, when administered in adequate amounts, confer a beneficial effect on the host" (as defined by the World Health Organization). Common probiotics include:
Lactobacillus (e.g., Lactobacillus acidophilus, Lactobacillus rhamnosus);
Bifidobacterium (e.g., Bifidobacterium longum, B. infantis);
Yeast (e.g., Saccharomyces boulardii). These strains play an important role in maintaining a balanced intestinal flora, enhancing immunity, and improving digestion.

2. The Relationship Between Probiotics and Diarrhea
Probiotics are commonly used to treat or prevent diarrhea.
Several studies have shown that probiotics have a positive effect on the following types of diarrhea:
Antibiotic-associated diarrhea (AAD): Antibiotics can disrupt the balance of intestinal flora, leading to diarrhea. Probiotics (such as Saccharomyces boulardii and Lactobacillus rhamnosus) can help restore the flora and reduce the risk of diarrhea.
Infectious diarrhea (such as rotavirus or bacterial infections): Certain probiotics can inhibit the growth of pathogens and shorten the duration of diarrhea.
Traveler's diarrhea: Probiotics may reduce the risk of infection by strengthening the intestinal barrier.

But why do some people experience diarrhea after taking probiotics?
While probiotics generally help improve diarrhea, some people may experience the following:
Temporary adjustments in the intestinal flora ("Herxheimer reaction"): When probiotics enter the intestines, they may alter the original bacterial composition, causing short-term discomfort such as bloating, diarrhea, or increased flatus. This condition usually resolves on its own within a few days to a week.

Unsuitable probiotic strain or dosage. Different strains of bacteria have different effects. Some strains (such as high-dose lactic acid bacteria) may stimulate excessive intestinal motility, leading to loose stools. Individuals also have varying tolerances to probiotics.

Products may contain harmful additives. Some probiotic supplements may contain lactose, fructose, or other fillers, which may cause diarrhea in people with lactose intolerance or sensitivity.

Immune system reactions (this is very rare). People with weakened immune systems (such as those with severe immunodeficiency) may experience an abnormal reaction to probiotics and should use them under the guidance of a doctor.

3. How to avoid diarrhea caused by probiotics?
Choose the right probiotic strain.
Probiotics for diarrhea: Saccharomyces boulardii, Lactobacillus rhamnosus GG, and Lactobacillus acidophilus have been extensively studied and shown to be beneficial.
Avoid unsuitable strains: If a particular probiotic causes discomfort, try switching strains or reducing the dosage.

Starting with a low dose and gradually adapting to probiotics can also help prevent diarrhea. When first starting, it's recommended to start with a low dose (such as 1 billion CFU), observe your body's response, and then gradually increase to the recommended dose (usually 5-10 billion CFU/day).
Also, pay attention to product ingredients and choose probiotics without additives (such as lactose-free and artificial sweeteners), especially for those with allergies.
In combination with dietary adjustments, ensure that users consume adequate dietary fiber (prebiotics), such as oats, bananas, and onions, to help the probiotics establish. Additionally, users should avoid high-sugar and high-fat foods to reduce intestinal burden.

4. Proper Use of Probiotics
Optimal Time of Use
On an empty stomach or before meals: Taking probiotics when stomach acid is low (such as in the morning on an empty stomach) helps more live bacteria reach the intestines. When taking multiple supplements at the same time, leave at least two hours between taking antibiotics to prevent the antibiotics from killing the probiotics.
Some probiotics require refrigeration (such as certain liquid probiotics), while thermophilic strains (such as spore-forming probiotics) can be stored at room temperature. Read the label carefully.
Are you still wondering if long-term use is safe?
For most people, long-term probiotic use is safe. However, your gut flora will naturally balance, so there's no need to rely on supplements permanently. We recommend using probiotics in phases (e.g., 1-3 months) in conjunction with a varied diet.

So, do probiotics cause diarrhea?
My answer: In most cases, no, but individual experience varies.
Probiotics are commonly used to prevent or treat diarrhea, but in rare cases, they can cause transient diarrhea due to strain incompatibility, excessive dosage, or individual sensitivity. Choosing the right probiotic, adjusting the dosage, and combining it with a healthy diet can maximize its benefits and minimize the risk of side effects.
If you experience persistent diarrhea after taking probiotics, it's recommended to change the strain or consult a nutritionist or doctor to find the best solution for your gut health.

Reference: 

https://health.clevelandclinic.org/best-time-to-take-probiotics

https://my.clevelandclinic.org/health/treatments/14598-probiotics

https://www.health.harvard.edu/staying-healthy/should-you-take-probiotics

https://www.nccih.nih.gov/health/probiotics-usefulness-and-safety