Many people take a daily probiotic supplement for its potential gut health benefits.
By maintaining or increasing the amount of what’s called “good” bacteria in the gut, probiotics are claimed to boost immunity, support urinary tract health, promote sleep, improve mood, aid weight loss and more.
There seems to be a probiotic for everyone these days. You’ll find formulations featuring different doses and types of bacteria that are tailored to kids, women, men and older adults.
Very specific strains of probiotics have been identified to help treat specific conditions, such as irritable bowel syndrome and ulcerative colitis, and provide symptom relief.
But can taking a probiotic supplement benefit already healthy people? Here’s what we know – and what we don’t.
What exactly are probiotics?
Probiotics are live micro-organisms, mostly bacteria but also yeasts, that when consumed in adequate amounts confer a health benefit.
They’re identified by their specific strain, which includes the genus, the species, the subspecies (if applicable) and the strain designation. For example, for the probiotic bacterium Bifidobacteria bifidum CUL-20, the genus is Bifidobacteria, the species is bifidum and the strain designation is CUL-20
Probiotics are similar to beneficial bacteria and yeasts that reside in our large intestine. Trillions and trillions of microbes call our gut home; along with their genethey make up what’s called our gut microbiome.
Our gut microbes extract energy and nutrients from dietary fibre, synthesize certain vitamins, activate protective phytochemicals, regulate immune function, inhibit the growth of harmful bacteria and protect the gut lining.
Growing evidence suggests that an imbalanced gut microbial community, termed dysbiosis, is associated with an increased risk of depression, obesity, inflammatory bowel disease, colorectal cancer and other diseases.
On the other hand, a gut microbiome that contains a diverse and balanced community of bacteria is tied to better health.
The idea behind taking a probiotic supplement is to help maintain a healthy balance of gut microbes.
The evidence for probiotics’ benefits in healthy people
A 2024 review of randomized controlled trials and meta-analyses, published in the journal Advances in Nutrition, concluded that there is sufficient evidence to use probiotics for some indications.
Many studies support taking probiotics to prevent antibiotic-associated diarrhea in children and adults ages 18 to 64.
Single probiotic strains with proven effectiveness are Saccharomyces boulardii and Lactobacillus rhamnosus GG. The evidence suggests starting probiotic treatment within two days of the first antibiotic dose.
Recent research is also pretty consistent that taking a probiotic supplement can help lower the risk of a respiratory tract infection and reduce the number of days of illness.
According to the review, there wasn’t strong enough evidence to broadly recommend taking probiotics to prevent urinary tract and vaginal infections in women, to guard against traveller’s diarrhea, to reduce antibiotic use for respiratory or gastrointestinal infections or to prevent heart disease.
Safety, potential downsides
Probiotics supplements are considered safe for healthy people and are generally well tolerated.
In people who have compromised immune systems or who are critically ill, however, probiotics may increase the risk of infection.
Some research suggests that probiotics may have unwanted effects in healthy people.
A study published in 2018 found that the gut microbiomes of participants given an 11-strain probiotic supplement for four weeks following a course of antibiotics took longer to return to normal. The prolonged dysbiosis lasted as long as six months.
In comparison, the gut microbiomes of those who did not take the probiotic supplement after antibiotics returned to normal within three weeks.
It’s also possible that taking a concentrated of amount of several probiotic strains could upset the balance of your gut microbiome by squeezing out some of the beneficial microbes you already have.
Probiotic strains may have different effects in different people depending on their unique microbiome.
There’s still a lot we don’t about the use of probiotic supplements in already healthy people.
The best way to sustain a diverse and balanced gut microbiome is to eat a fibre-rich diet that includes plenty of whole plant foods such as vegetables, fruit, whole grains and pulses.
Include good sources of prebiotic fibres in your diet, which feed beneficial gut bacteria promoting their growth and activity.
These include oats, barley, apples, banana, berries, artichokes, asparagus, dandelion greens, garlic, onion, tomatoes and white kidney beans.
Add fermented foods to your diet too, such as yogurt, kefir, kombucha, kimchi and unpasteurized sauerkraut. These foods are natural sources of a mixture of probiotic microbes.
If you have a health condition and are wondering about probiotics, speak to your doctor, dietitian or pharmacist to find the correct strain, if any, that has been studied for your condition.
Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan. Follow her on X @LeslieBeckRD
