Research

Caveat emptor

“Probiotics” might not be what they seem

Brenda A. Huff, MD, CCFP

This article has been peer reviewed. Cet article a fait l’objet d’une évaluation externe. Can Fam Physician 2004;50:583-587.

Dr Huff is a second-year family medicine resident in Chilliwack, BC.

Probiotics is a broad term that refers to the concept of feeding live microbial organisms to human beings with the goal of preventing and treating disease. The word probiotic is derived from a Greek term and means “for life.” The first reference to health benefit dates back to the early 1900s when the Nobel prize–winning Russian physician Elie Metchnikoff hypothesized that Bulgarian peasants lived long, healthy lives because they consumed fermented milk products.1

In the last century, many proponents of probiotic treatment have cited various benefits: “maintains healthy digestion,” “assists in general well-being,” “builds immunity, adding years to your life.” Much of the enthusiasm for probiotic treatment is among proponents of what might be termed alternative medicine. With any commonly used Internet search engine you will get more than 16 000 sites referencing the word. It is hardly a surprise that sales are soaring.2

Although probiotic preparations have been available commercially for years, data on their benefits and mechanism of action remain scarce.3 Possible mechanisms include the synthesis of antimicrobial substances, competition for nutrients required for growth of pathogens, modification of toxins or toxin receptors, and stimulation of nonspecific immune responses to pathogens.4

In recent decades, Bifidobacterium, Saccharomyces boulardii, and Lactobacillus have been investigated for their probiotic potential. One of the most commonly studied probiotic organisms is Lactobacillus casei subsp rhamnosus (LGG).5 Studies attempt to show benefit in prevention and treatment of various illnesses (such as diarrhea, urinary tract infections, irritable bowel syndrome, yeast infections, cancer, and hypertension) but fail to demonstrate sound evidence.6

A few rigorously controlled scientific trials have been conducted. Recently, a systematic review of published, randomized, double-blind, placebo-controlled trials demonstrated clinically significant evidence that probiotic organisms (in particular LGG) are beneficial in reducing the duration of acute infectious diarrhea in children.7 Other trials have demonstrated benefit from probiotic treatment in ameliorating symptoms of antibiotic-associated diarrhea among children.8 In these studies meticulous care was taken to keep the probiotic organisms in their “live” form. Statistical heterogeneity was noted across the studies. There were differences in both the dosage and duration of treatment. Importantly, products cited in these particular studies contained at least 10 times more probiotic organisms than commercially available products do.9

While no obvious adverse effects from these products have been reported in any study, information is limited.10 Geralk Tannock in Horizon Scientific Press says “the pathogenicity of lactobacilli is generally low; one case has been reported in which a probiotic lactobacillus was found associated with a liver abscess.”11

So what are physicians’ attitudes toward their patients’ use of probiotic products? A recent survey, published in the Canadian Medical Association Journal asked whether physicians recommend probiotic treatments to their patients to prevent antibiotic-associated diarrhea.12 Of the 68% who responded, 32% reported that they recommend probiotic products to their patients when prescribing antibiotics.

Some concerns, especially in a UK study published in the British Medical Journal,13 have been noted about the contents of commercial probiotic preparations. The microbial content of 13 different brands bought over-the-counter in Britain was investigated. This study revealed species that were not listed on their labels and numbers of viable cells far lower than those stated by their manufacturers.

Many people are buying probiotic products off the shelf, and some physicians are, at least in part, recommending these products to their patients. This project was undertaken to answer the following questions. Are North American commercial probiotic preparations viable? Do they contain Lactobacillus as stated on their labels? What is the quantity of lactobacilli in each product? Do these products contain species not listed on their labels?

METHODS

I purchased, at random, 10 different brands of probiotics from six different retail stores in BC’s lower mainland. Most medical studies used Lactobacillus species; therefore I chose only products claiming to contain this bacterium. I complied with instructions on the containers and refrigerated as directed.

The preparations were aseptically transferred from their original containers to sterile screw-topped tubes. A microbiologist then took the specimens to the laboratory to be cultured. Both the person transferring the powder and the microbiologist were blinded to the contents of the preparations (Table 1).

The objective was to determine whether the products did, in fact, contain viable bacteria. Each product was cultured twice under appropriate conditions. The cultures were examined to determine whether Lactobacillus species grew as stated on each container.

Colonies on each Petri dish were quantified. I compared my results with the quantity labeled on each product. Species other than those listed on the product containers were identified and recorded. Due to the limitations of this study, I was unable to identify all species contained in each sample. All products were manufactured in North America.

RESULTS

None of the products matched their labeled microbiologic specifications qualitatively or quantitatively (Table 2). Two of the 10 probiotic products cultured (specimens A and D) grew nothing. Four brands (A, D, E, and I) did not grow the Lactobacillus species listed on their labels. Four brands (B, C, E, and G) contained species not listed on the label (Enterococcus faecium, Bifidobacterium, Streptococcus oralis). Some of the species not listed on the label were found to be resistant to ciprofloxacin. This was an incidental finding of unclear importance.

Each brand quantified the bacterial species listed on its label differently. Specimen E did not quantify at all. Some products quantified per capsule, others quantified all species into one number, and yet others used percentages. The number of probiotic organisms per capsule, as claimed by manufacturers, ranged from 2 to 20 billion. My results ranged from 20 to 80 million.

DISCUSSION

Using lactic bacteria to treat human disease is not a new concept. Recent studies report evidence in favour of probiotic products for treating specific conditions. Standardized scientific analysis precisely defining and quantifying each probiotic strain is still required. In theory, if probiotic treatment is proven beneficial in reducing illness, the cost of medical care will be reduced, stays in hospital will be shorter, and fewer days will be lost from work.

This study found that commercially available over-the-counter products were inaccurately labeled. Some products tested contained only dead bacteria. Most labels did not adequately identify the microbes in their products. Lactobacillus was listed among the contents of each product but was found in only half the samples and in numbers one tenth their stated concentration. There were inconsistencies in the nomenclature and quantification of these products. Extra species not listed on the label were identified. It was impossible to identify all organisms in each product due to lack of funding.

No current government regulations apply to over-the-counter probiotic products.14 The public has no guarantee that these products contain viable organisms or that they contain the species listed on their labels. Many of the products tested contained species other than those listed, none of which are known to be harmful. Without government regulation, however, products that contain harmful bacteria could be on the market.

Growing public interest in wellness has fueled demand for more probiotic products. In an attempt to support our patients, and in light of the low toxic effects, many physicians do not advise against using these products.

This study has some limitations. It is possible that mostly unsuitable brands were chosen, although the choice was random. The testing was carried out in only one laboratory, although the method was explicit and standardized.

CONCLUSION

This study indicates that many commercial probiotic preparations do not contain the active ingredients listed on their labels. Consumers essentially are buying products that have no proven benefit and are not what they claim.

Acknowledgment

I offer special thanks to Dr Dale Purych, medical microbiologist at Chilliwack General Hospital in the Fraser Valley Health Authority in British Columbia.

Competing interests

None declared

Correspondence to: Dr Brenda Anne Huff, Box 234, New Aiyansh, BC V0J 1A0; e-mail bhuff@nisgaahealth.bc.ca

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