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Top ten most asked questions in my practice (with typical answers)

Bradley Linton, HBSc., BSc Pharm., Pharm D, RPh

1. Probiotic Indication & Effectiveness:

Should I take a probiotic if I am experiencing diarrhea (acute)? What is the best probiotic to take if I am experiencing diarrhea (acute)?

The most important treatment for diarrhea is still hydration and electrolytes, not probiotics. However, probiotics are not harmful when experiencing acute diarrhea. Furthermore, there is evidence to suggest that the addition of probiotics may reduce the symptoms.1 Whenever I recommend a probiotic, I always ensure I recommend one with an eight-digit Natural Product Number (NPN), as this ensures the product has been reviewed by Health Canada for safety and high quality. For diarrhea (not antibiotic-associated), I usually suggest a combination product that includes Lactobacillus and/or Saccharomyces.

2. Probiotic Indication & Effectiveness:

What is the best probiotic to take if my bowel movements are not regular?

Talk to your doctor to have proper tests and assessments to rule out any serious conditions (like Crohn’s Disease, Ulcerative Colitis, etc). Once those have been completed, a trial of probiotics is not unreasonable. I typically recommend products that have Bifidobacterium and/or Lactobacillus in the ingredients, as these products have the most evidence in patients with irregular bowel movements.

3. Probiotic Indication & Effectiveness:

Should I try a probiotic if I suffer from recurrent yeast infections?

You may need to see a gynecologist and receive all appropriate assessments first. After those are done and specific conditions have been ruled out, it is not unreasonable to trial a probiotic. Using a probiotic reduces yeast and bacteria on vaginal surfaces for vaginal health.2 Most of the studies performed on women with recurrent yeast infections used a formulation that contains Lactobacillus, so this is what I recommend to try. Purchase a bottle of at least 30 capsules and take it daily until the bottle is finished.

4. Probiotic Storage:

I notice that some are kept in the fridge, why is that? Are these ones better? Should I store my probiotics in the fridge?

Some probiotics need to be stored in the fridge while others do not. Always read and follow the directions for storage on the probiotic product purchased. Certain strains are more sensitive to higher temperatures and can be killed when exposed to high temperatures. Product manufacturers generally perform stability studies to determine if their probiotic requires refrigeration or can be stored at room temperature. Just because a probiotic is stored in the refrigerator does not mean it is more or less effective than a product stored at room temperature.

5. Probiotic Effectiveness:

Should I take probiotics to reduce the risk of diarrhea when using my antibiotic?

To minimize the risk of diarrhea while using an antibiotic, I suggest using a probiotic during the antibiotic course. Probiotics that contain Lactocaseibacillus Rhamnosus GG and/or Saccharomyces boulardii are recommended, as these strains have been studied more than others. Start the probiotic when initiating the antibiotic course and continue taking it until at least 3 days after the antibiotic course is finished.

There are some populations that I almost always recommend using a probiotic when starting an antibiotic and this includes:

  • • Patients with a history of Clostridium difficile (C. diff) infection
  • • Patients with a history of severe, antibiotic associated diarrhea
  • • Patients with irritable bowel syndrome
  • • Frail elderly patients on antibiotics most likely to cause diarrhea (fluoroquinolones, clarithromycin, etc.)

However, taking a probiotic does not guarantee that you will not experience antibiotic associated diarrhea, but it will decrease the likelihood of experiencing it.

6. Probiotic Interactions:

Do antibiotics kill the probiotics? How do I counteract this?

There is a theoretical concern that antibiotics will kill the probiotics if taken simultaneously. Because of this concern, I suggest spacing out antibiotics and probiotics by at least two hours whenever possible. However, if this is difficult to achieve, they may be taken together as there is no safety concern when doing this (they could be less effective though).

7. Probiotic Interactions:

I am on numerous medications for various conditions. Is a probiotic safe to take regularly?

Aside from the theoretical interaction with antibiotics, there are no identified drug-drug interactions with any other medications. The only population that should avoid probiotics due to safety concerns are patients who are immunocompromised. This group includes patients on high-dose steroids, chemotherapy, cancer, etc. In addition to these populations, there is not enough evidence to recommend using probiotics during pregnancy or breastfeeding at this moment.

8. Prebiotic vs Probiotic:

I have heard of prebiotics now. What is the difference between prebiotics and probiotics? Are prebiotics better?

Prebiotics are not the same as probiotics. Prebiotics are indigestible, high fiber food products that stimulate the growth of healthy gut bacteria.3 Examples of such foods are bananas, greens, whole grains, and many others.4 While eating these foods is generally considered safe. Prebiotics are abundant in many of the foods we consume regularly in a typical diet.

9. Probiotic Effectiveness:

How will I know if the probiotic is working? Will I see an immediate effect?

The onset of effect is generally dependent on the reason the probiotic is being used. Acute conditions, such as diarrhea, may show improvement within 48 hours. For most conditions, I usually suggest trying the product for one month (a bottle of 30) and seeing if there is any improvement.

10. Yogurt and Probiotics:

Can I just use yogurt instead? It has probiotics, right?

Yogurt is generally considered a healthy food to eat and is full of nutrients such as protein, calcium, vitamins, and good bacteria (probiotics). Some types of yogurts have been studied and show a positive effect for certain conditions. I recommend eating yogurt as part of a healthy, balanced diet, however, the majority of the evidence with probiotics is found with supplements.


  1. 1. Huang R, Xing HY, Liu HJ, Chen ZF, Tang BB. Efficacy of probiotics in the treatment of acute diarrhea in children: a systematic review and meta-analysis of clinical trials. Transl Pediatr. 2021 Dec;10(12):3248-3260. doi: 10.21037/tp-21-511. PMID: 35070839; PMCID: PMC8753473.
  2. 2. Xie HY, Feng D, Wei DM, et al. Probiotics for vulvovaginal candidiasis in non-pregnant women. Cochrane Database Syst Rev 2017; 11:CD010496.
  3. 3. Ford AC, Harris LA, Lacy BE, et al. Systematic review with meta-analysis: the efficacy of prebiotics, probiotics, synbiotics and antibiotics in irritable bowel syndrome. Alimentary Pharmacology & Therapeutics. 2018;48(10):1044-1060.
  4. 4. Probiotics: What You Need to Know. National Center for Complementary and Integrative Health.,Influence%20your%20body's%20immune%20response. Accessed May 31, 2023.