Do probiotics really benefit healthy people?

A recent study published in the journal Advances In Nutrition reviewed the evidence of the benefits of probiotics for healthy people.

Probiotics are microbes that confer health benefits to the host. Various studies have examined the use of probiotics for diverse conditions for patients and healthy individuals. Clinical trials have also investigated different outcomes in relation to probiotic use. However, a common question remains: should everyone take probiotics? This study reviewed the available evidence to assess the outcomes of probiotic use in healthy people.

The research team assembled experts to explore the evidence, following the United States Preventive Services Task Force (USPSTF) approach. This review primarily focused on healthy individuals and also considered population subgroups. The study explored whether probiotics could prevent infections of the vaginal, respiratory, gastrointestinal (GI), or urinary tract, reduce antibiotic use, or improve cardiovascular risk factors.

Study: Is there evidence to support probiotic use for healthy people? Image Credit: Orawan Pattarawimonchai / Shutterstock

Urinary and vaginal tract infections

Urinary tract infection (UTI) is the most prevalent bacterial infection worldwide, accounting for one-fourth of infections in females. In a trial, weekly vaginal application of suppositories containing Lactocaseibacillus rhamnosus GR-1 and Limosilactobacillus fermentum B-54 for one year reduced the recurrence rate of UTIs. However, a similar result was observed for 21 subjects who received a prebiotic in skim milk.

In another study, young females with a history of UTI recurrence had fewer recurrent episodes after taking a probiotic (Lactobacillus crispatus CTV-05) compared to placebo recipients. Further, oral administration of Lactobacillus reuteri RC-14 and Lacticaseibacillus rhamnosus GR-1 reduced UTI recurrence relative to antibiotic therapy. Vaginal tract infections are highly prevalent, caused by yeast, bacteria, and viruses, and are characterized by the disruption of normal microbiota.

Probiotics have been used to replenish vaginal microbiota with lactobacilli that inhibit pathogens and interrupt biofilm formations. Oral and vaginal administration of probiotics has been investigated. In one trial, females with bacterial vaginosis (BV) or recurrent BV were treated with vaginally administered Lactobacillus crispatus IP 174178 capsules; the use of probiotics was associated with a reduced BV recurrence.

In a different study, subjects were asked to report BV occurrence and symptoms of thin discharge or malodor. They were randomized to receive a placebo or intravaginal capsules of Streptococcus thermophilus, Lactobacillus acidophilus, or Lacticaseibacillus rhamnosus. The study found lower BV recurrence rates in the probiotic group than in the placebo group.

Respiratory and GI tract infections

Much research on probiotic use has focused on the prevention of antibiotic-associated diarrhea (AAD), which occurs during or after antibiotic use. Various systematic reviews have reported that most probiotics can reduce the risk of AAD. A meta-analysis revealed that using both antibiotics and probiotics can reduce AAD risk by 37%.

Other meta-analyses have observed that probiotics, such as Lacticaseibacillus rhamnosus GG and Saccharomyces boulardii, are highly effective compared to placebo or no intervention. Travelers’ diarrhea (TD), a common health concern for travelers, is more likely to occur when traveling from developed to less-developed regions. A systematic review compared the efficacy of probiotics and rifaximin in TD prevention.

While rifaximin and probiotics were associated with reduced TD incidence relative to placebo, rifaximin was more effective. Respiratory tract infections (RTIs) are a significant public health concern. Evidence on the use of probiotics to prevent RTIs is mainly derived from clinical studies that have cumulatively involved thousands of healthy adults and children. Meta-analyses of these studies have consistently reported that probiotics decrease the risk and incidence rate of RTIs.

Cardiovascular health

Cardiovascular disease (CVD) is the global leading cause of death. Given the slow progression of CVD, studies have not examined probiotics for CVD prevention. Nonetheless, probiotics have been investigated in relation to cardiovascular risk factors, including obesity, hypertension, and glucose metabolism.

One study evaluated the impact of different probiotics on variables related to non-alcoholic fatty liver disease, obesity, and diabetes and noted that probiotics slightly but consistently improve multiple metabolic risk factors. Further, supplementation of probiotics or synbiotics (a combination of prebiotics and probiotics) caused a reduction in total cholesterol levels in individuals with metabolic syndrome.

A meta-analysis found that synbiotics increased high-density lipoprotein cholesterol levels and reduced serum insulin, low-density lipoprotein cholesterol, total cholesterol, triglycerides, systolic blood pressure, body weight, and weight circumference. These findings were statistically significant and clinically relevant.

Concluding remarks

In sum, the available efficacy data for assessed endpoints are insufficient to provide preventive recommendations. However, this does not imply that the data are inadequate to be considered for healthy populations. Notably, research on probiotics is relatively new, and the lack of evidence does not reflect inefficacy. Although there was evidence of the preventive benefits of probiotics for some indications, more research is needed. Overall, this review might encourage funding sources and researchers to pave the way for further work on probiotics.