A research study looking into the effects of probiotics supplements on gut bacteria found nothing in terms of beneficial outcomes in healthy adults. The study was published in Genome Medicine on May 10, 2016.

Global sales for probiotics products in the form of food, supplements, and drinks are predicted to reach 29 billion pounds by the year 2018. Every 6 in 10 households in Britain consume probiotics products like Yakult and Actimel.

In United States, data from the year 2013-2014 shows a 14% increase in their global sales, in which 1.5 billion dollar sales were made in States, out of the total global sales of 2.4 billion dollars.

The systematic study conducted at the University of Copenhagen in Denmark used the data from different online information portals, in the form of scientific studies exploring the effects of probiotics in healthy adults in a population. A total of seven studies were selected to be analyzed out of the initial cohort of 1,368. All of the studies were published between February 2013 and October 2015 in Italy, United States, Denmark, Finland, and Germany.

The studies were modeled after randomized control trial designs and one of them used a crossover design. One study was single blinded while the others were all double blinded.

Out of each included study, information like characteristics of the participants, such as their age and gender, along with information regarding interventions in the form of probiotics strain and respective dosages, study design including duration and model, and outcome measures in the form of effect on the structure of gut bacteria and micrbiomes, was extracted.

The structure of gut bacteria was accessed on the basis of abundance, richness, evenness, compositional dissimilarity (β-diversity) or α-diversity.

Total participants were in the range of 21-81 and between the ages of 19 to 88. Probiotics were given to them in different forms, including milk based drinks, biscuits, sachets, and capsules. The probiotics given were Lactobacillus in five studies, Bifidobacterium and Lactobacillus combined in one trial and Bacillus in another.

Study results showed no effects on fecal microbes used to access the effectiveness of the probiotics. Only one paper reported modified structure of the bacterial colony in the form of compositional dissimilarity (β-diversity) in comparison to the placebo.

The senior researcher Nadja B Kristensen, at Section for Metabolic Genetics in Faculty of Health and Medical Sciences, University of Copenhagen, pointed out several limitations of the review study. She said that different study designs and styles of reporting results made it difficult to compare them with each other. Moreover, the research on the subject is very rare. Sample sizes are small, making it difficult to generalize results and demographic variations are present, restricting homogeneity and there is presence of publication bias.

The lead author Oluf Pedersen commented that there was evidence from previous reviews that probiotics intake may benefit people with disease- associated imbalances of gut microbes but there was little similar effect in healthy individuals.

The team called for more research in this specific area to get non challenge able results with studies of better design, precise reporting of results, known dosages and experimentation with newer strains of probiotics.

The funding was provided by the Novo Nordisk Foundation, which was not involved in  any stage or process of the research.

United States Food and Drug Administration classifies these products as dietary supplements, and these products are readily available in the market for public consumption, with minimal regulations.

National Center for Complementary and Integrated Health (NIH), US, recommends these supplements to be used for digestive disorders like diarrhea, irritable bowel syndrome, inflammatory bowel disease, allergic disorders like eczema, hay fever, tooth decay, periodontal disease, colic in infants, liver disease, and even common cold.

NIH also cautions that the recommendations are based on preliminary studies and not much is known about which types of probiotics are helpful and which are not. The website explains that though some promise has been shown, concrete evidence is ‘lacking’.

FDA has not yet approved the use of these supplements to be used ‘for preventing or treating any health problem.’

National Health Service (NHS) UK lists several studies as evidence regarding the benefits of these supplements in treatment of diseases.

These studies include use of probiotics to prevent antibiotic associated diarrhea, treating and shortening the episode of infectious diarrhea, helping newborns fight off necrotizing enterocolitis (NEC) where gut tissue becomes inflamed and starts to die, helping reduce bloating and flatulence in people with irritable bowel syndrome, helping reduce symptoms of lactose intolerance, as well as helping treat pouchitis (where people who have undergone surgery as a result of ulcerative colitis, get their constructed loop of bowel inflamed).

Other contradictory studies to NIH recommendations show that probiotics do not help treat colic in children, do not boost your immune system, and neither do they help with treatment of bacterial vagionsis and vaginal thrush. These products do not show any beneficial effect in treating eczema either.