The gut microbiome is comprised of all of the microorganisms — good and bad — living inside the human gastrointestinal tract. The composition of this microbiome is largely affected by diet and medications, specifically antibiotics. Disruption of the microbiome can significantly impact the immune system, increasing risk of infection, decreasing bioavailability of nutrients and intestinal barrier function, and in turn affecting the overall health of an individual.
Introducing probiotics to the gut via supplementation may enhance the body’s immune system defenses and aid in acute response to harmful pathogenic bacteria in the gastrointestinal tract. Probiotics are live microorganisms that when taken in sufficient amounts provide benefits to the consumer. Decreased severity of antibiotic-associated or infectious diarrhea, constipation and abdominal bloating and distention in irritable bowel syndrome, or IBS, are just a few of the benefits that have been shown to occur with consistent consumption of probiotic supplements.
With so many probiotic supplements on the market, how do you choose the right one? 
There are many factors to consider when choosing a probiotic including the storage temperature, number of colony forming units, or CFUs, and types of bacterial strains included in the supplement.
Here are a few items to consider when selecting and taking a probiotic supplement:
1. Review the Storage Recommendations
Currently, there is no research to suggest that refrigerated probiotic supplements are more effective than their room temperature counterparts. Store your probiotic supplement as recommended by the manufacturer in order to reap the full benefits.
2. Look for a Supplement that Contains at Least 106 to 109 CFUs
According to recent research, this is the minimum amount of CFUs that must reach the intestines in order to provide benefits.
3. Know What Strains You Need
Discuss any medical conditions with your doctor and dietitian prior to selecting your probiotic. Recent studies suggest certain strains of bacteria can provide symptom relief for those with antibiotic-associated diarrhea, acute onset infectious diarrhea, IBS and IBD. For example, Lactobacillus rhamnosus GG has been suggested to reduce length of symptoms with acute infectious diarrhea and antibiotic-associated diarrhea. Additionally, for patients with IBS, a probiotic supplement with a combination of species including Bifidobacteria is recommended rather than a single species Lactobacillus probiotic.
4. Be Aware of Other Ingredients
If you have food allergies or intolerances be sure to read the supplement facts label carefully for inactive ingredients. Many probiotics will list on their label if they are free from major allergens such as gluten, dairy, soy or nuts.
5. Take Your Probiotic Daily
Probiotics may provide benefits in a variety of ways, beyond just altering the composition of the gut microbiome. However, in order to continue to reap the benefits of a probiotic supplement, continuous consumption is needed. Studies have shown that the effects of probiotic supplementation are no longer detectable one to four weeks after individuals stop taking their probiotic supplement.
What about Food Sources of Probiotics?
Many fermented dairy products contain active Lactobacillus strains. However, they typically are not present in quantities large enough to provide benefits. If a fermented food product is fortified with additional probiotics meeting the 106 to 109 CFUs level, it may be considered a probiotic supplement and provide benefits.
Probiotic supplements are considered safe for most populations, but are not recommended for the critically ill or individuals with a compromised immune system. Possible side effects when starting to take probiotics include gas and bloating, but typically these side effects are short-term. It is important to talk with your doctor before taking a probiotic supplement.
