Nutrasource Blog

Probiotics, Allergies and the Evaluation of Clinical Studies

Posted by Dr. Carolina Bonilla, MD/PhD on Thu, Feb 18, 2016


In the second installment of our Physician's Insights blog series, Dr. Carolina Bonilla, MD/PhD, explains clinical research best practices for probiotics, including lessons learned from recent probiotic trials conducted in humans.Dr._Carolina_Bonilla.jpg

In the area of immunology, there is growing evidence that certain nutrients such as probiotics, prebiotics, symbiotics (nutritional supplements combining pre and probiotics), antioxidants, some vitamins and folate could have a potential effect on immune function.

The notion of probiotics was probably first introduced by a Ukrainian zoologist and immunologist Elie Metchnikoff, in 1907. The term probiotic derives from the Latin word “pro” and the Greek word “bios” meaning for life. Metchnikoff proposed the idea of colonizing the gut with beneficial flora.

Not all probiotics are created equal

Probiotics have the characteristic of recolonizing and restoring microflora in the intestinal tract. Not all probiotics are the same, however, and several requirements need to be met to define a good probiotic (1). These include:

  • “The probiotic’s ability to adhere to gut epithelium cells
  • The capacity to exclude or reduce pathogenic adherence
  • The faculty to persist, multiply and produce acids, hydrogen peroxide and bacteriocins against pathogenic growth”.

The two most common types of probiotic bacteria are Lactobacillus acidophilus and Bifidobacterium bifidus. Additionally, the different strains include L. rhamonusus, L. bulgaricus, L. salivarius, L. plantarum, L. casei, as well as B. infantis, B. longum, and Streptococcus thermophilus. As for yeast, a common probiotic is Saccharomyces boulardii.

An article published by Castellazzi and Cols, 2013 explains with detail the use of probiotics in allergies, specifically their ability to adhere to the intestinal epithelium, promote intestinal microbiotic equilibrium, and activate the immune system to provide protection against unwanted pathogens.

The role of probiotics in the allergic response

As human beings, we are frequently and continuously exposed to abundant food allergens; yet, only a minority of us develops an allergic response with clinical symptoms.

There are two types of basic allergic reactions: IgE and non-IgE mediated allergic reactions. IgE allergic reactions are most common. In addition, personal or familial predisposition to produce IgE antibodies is known as “atopy” (from the Greek atopos, meaning out of place). Atopic individuals are particularly susceptible to develop allergies even with low doses of allergens, including food allergies, hayfever, allergic rhinitis, atopic eczema and asthma.

The use of probiotics and its role in allergy disease has been widely investigated, particularly in food allergies, atopic dermatitis, the respiratory system and gastrointestinal tract. In human studies the results are mixed, from positive results to no benefits including single studies, systematic review and meta-analyses.

Lessons from the body of clinical literature on probiotics

The evaluation of studies assessing probiotics in humans could be somewhat problematic, and certain aspects are important for consideration:

  • As discussed above, probiotics commonly derivate from bacteria or yeast. Probiotics from bacteria have over 8 different strains the combination of these microorganisms and their dose in humans can often produce differing study results.
  • The type of the allergy must be considered when evaluating the efficacy of probiotics. Most of clinical studies have evaluated its use in eczema and gastrointestinal disease (GI) with mixed results. Of note, certain types of probiotic strains are found to be valuable in the treatment of certain GI diseases; however, this is not the case for the treatment of eczema. More studies are needed in food allergies.
  • Special attention is being placed in pregnant mothers, new mothers and infants to reduce atopic reactions within the first two years of life. The elderly continues to be the most understudied population for probiotics.
  • And, in most studies, the duration of use of probiotics runs from a couple of weeks to up to two years in comparison with placebo; again, no conclusive statements can be made in relation to the time of exposure.

In conclusion, there is a notable interest in the scientific community about the use of probiotics for the prevention and treatment of allergy disease. In order to evaluate probiotics’ use in clinical studies, it is important to consider certain aspects, and therefore develop new lines of investigation around this fascinating area of growing research.

Considering a clinical study for probiotics or prebiotics?

Contact our clinical trials team today to learn about our onsite and multi-centre research capabilities at Or click to get a customized quote.

About the Author:

Dr. Carolina Bonilla, MD/PhD, Medical Research Advisor and Sub-Investigator at Nutrasource, brings over 14 years of experience in coordinating and supervising clinical trials and health research projects. Dr. Bonilla specializes in chronic disease prevention and management including diabetes, hypertension, hypercholesterolemia and weight management.

1. EFSA 2004, Scientific Colloquium Summary Report. QPS: qualified presumption of safety of microrganisms in food and feed. via Carlo Magno 1A- 43126 Parma, Italy: EFSA (Autorità Europea Sicurezza Alimentare)


Topics: Nutrition, Clinical Research, Research