Expired probiotics: what is really in your cabinet?

The popularity of using probiotics has surged, since they became widely accepted as safe and help improve general health. Inevitably, some of these products are used after expiration when microbial cell viability is below the recommended effective dose. Given that probiotics must be live microorganisms administered in adequate amounts, the aim of this study was to measure viability in expired products and assess how packaging and storage conditions impact efficacy, if at all. Thirty-three expired probiotic products were evaluated, of which 26 were stored in conditions recommended by the manufacturer. The viable microbial cells were enumerated and representative isolates identified by 16S and internally transcribed spacer rRNA gene sequencing. While the products had a mean past expiration time of 11.32 (1–22) years, 22 still had viable contents, and 5 were within or above the original product cell count claim. Product formulation and the number of species present did not appear to impact the stability of the products. However, overall packaging type, storage conditions and time since expiry were found to affect viability. All products with viable cells had the strain stipulated on the label. Despite some selected probiotic products retaining viability past their expiry date (indicating long-term storage is possible), the total counts were mostly well below that required for efficacious use as recommended by the manufacturer. Consuming expired probiotics may not yield the benefits for which they were designed.