Numerous evaluations – both published and unpublished – have suggested that probiotic products do not always contain the level or types of microbes that they claim to contain.1, 2 In the United States, accurate product labeling is a fundamental responsibility of manufacturers required by Good Manufacturing Practices, which exist for both supplements and foods. Furthermore, labels are required to meet the FDA standard of being “truthful and not misleading.” Therefore, all commercial probiotic products should match what they claim on their labels. Products not accurately labeled are, strictly speaking, misbranded. But products on the store shelves are generally not scrutinized by regulatory agencies and therefore misbranded products surely exist.
So how should we interpret studies that report that some probiotic products don’t meet label claims?
The first option is that studies may be accurately identifying sub-standard products. In this case, the consumer would be wise to choose other products. However, it is also possible that a given study may underestimate the number of live probiotics in a product due to use of sub-optimal methods for enumeration or unrepresentative samples. Experimental results are only as good as the methods used to generate those results. Survey studies typically choose one basic method to enumerate a range of products. Yet one method is unlikely to be optimal for all strains in all products. The method used to reconstitute dried probiotics; the growth media utilized (with or without selective ingredients); and incubation temperature, atmosphere, and time chosen for growth will all affect the number of colony-forming units that emerge in plate counts. In addition, injured (but still alive) microbes may not grow under suboptimal conditions. Modern methods based on PCR or other DNA-based approaches may yield different results, too. Therefore, acceptable products may be singled out as sub-standard when there is not a scientific basis for this conclusion.
A measure of skepticism is thus in order when considering results of probiotic enumeration surveys. As Lahtinen et al.3 explains, “We conclude that the choice of enumeration method for probiotic bacteria may have significant effect on the results of the analysis. The strain-specific properties and the objects of the analysis should be taken into account when enumeration methods for different probiotic strains are chosen.”
What consumers should know
Meeting label claims is important. But what is more important is that the particular probiotic formulation works for you. If it works, don’t sweat the numbers.
In my opinion, delivering the labeled concentration of live probiotics through the end of shelf life is one mark of quality of a product. But published results are only as good as the methods used to generate them, and therefore enumeration studies on probiotic products should be carefully considered. It is not unreasonable for a company to dispute findings from an external evaluation based on authors’ use of suboptimal methods. However, a company should make available methods specific for their product so their counts can be validated by a third party.
Stability over the course of shelf life is not only a problem for probiotic products. All supplements (and drugs for that matter) will diminish in potency over time. Heed the “use by” date and store according to manufacturers’ instructions. Probiotics, being live microbes, are especially vulnerable to factors that impact stability over time. Market pressures drive companies that sell dietary supplement forms of probiotics to claim their products are stable at room-temperature storage for up to 24 months on the shelf. Such stability is a sizable technological challenge, which not all commercial products meet. Probiotics in dairy products are typically refrigerated products with a comparatively short shelf life. Maintaining viability under these conditions is easier to attain.
Available probiotic products today may be better than those in the past. A recent publication by Goldstein et al.4 enumerated four commercial probiotic products (Align®, Bio-K+®, Culturelle® and Lactinex®) that listed minimum viable counts. (Florastor®, which contains a yeast, was also assayed, but its label lists grams, not cfu). Together these products contained four species of Lactobacillus (acidophilus, casei, rhamnosus and helveticus) and Bifidobacterium infantis (more correctly known as a subspecies of B. longum). All products contained live probiotics at or above the minimum amount stated to be in the product at the end of shelf life.* These results are encouraging and suggest that – at least for the brands tested here – companies are marketing products that meet their label claim.
*Note that for the Align® product, the average count per dose/serving was reported by Goldstein et al. as 6.1×108 cfu. The product label indicates a count of 1×109 cfu at time of manufacture. The Align website indicates the product will have a minimum count of 1×107 cfu at the end of shelf life.
- Sanders ME, Heimbach JT. 2004. Functional foods in the USA: emphasis on probiotic foods. Food Sci Technol Bull 1(8): 1-10. (See Tables 1a and 1b.)
- Product Review: Probiotics for Adults, Children and Pets. ConsumerLab.com (Fee required for full report)
- Lahtinen SJ, Gueimonde M, Ouwehand AC, Reinikainen JP, Salminen SJ. Comparison of four methods to enumerate probiotic bifidobacteria in a fermented food product. Food Microbiol. 2006 Sep;23(6):571-7.
- Goldstein EJ, Citron DM, Claros MC, Tyrrell KL. Bacterial counts from five over-the-counter probiotics: Are you getting what you paid for? Anaerobe. 2013 Nov 1. pii: S1075-9964(13)00172-8. doi: 10.1016/j.anaerobe.2013.10.005. [Epub ahead of print] PMID: 24184290
Other related references:
Ashraf R, Shah NP. Selective and differential enumerations of Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus casei and Bifidobacterium spp. in yoghurt–a review. Int J Food Microbiol. 2011 Oct 3;149(3):194-208.
Aureli P, Fiore A, Scalfaro C, Casale M, Franciosa G. National survey outcomes on commercial probiotic food supplements in Italy. Int J Food Microbiol. 2010 Feb 28;137(2-3):265-73.
Dunlap BS, Yu H, Elitsur Y. The probiotic content of commercial yogurts in West Virginia. Clin Pediatr (Phila). 2009 Jun;48(5):522-7.
Masco L, Vanhoutte T, Temmerman R, Swings J, Huys G. Evaluation of real-time PCR targeting the 16S rRNA and recA genes for the enumeration of bifidobacteria in probiotic products. Int J Food Microbiol. 2007 Feb 15;113(3):351-7.
Oberg CJ, Moyes LV, Domek MJ, Brothersen C, McMahon DJ. Survival of probiotic adjunct cultures in cheese and challenges in their enumeration using selective media. J Dairy Sci. 2011 May;94(5):2220-30.