Understanding Probiotics & Stability

What are Probiotics?

Probiotics are live beneficial microorganisms (e.g., bacteria, yeasts) that are either the same as or similar to microorganisms found naturally in or on the human body. They play a crucial role in helping the body function and are beneficial to health.  

The body, especially the lower gastrointestinal tract (the gut), contains a complex and diverse community of microorganisms often referred to as microbiota or microflora. These microorganisms are estimated to outnumber human cells by a factor of ten to one in the body of a healthy adult. 

Measurement Standards

Probiotics are measured using colony-forming units or CFUs. The CFU amount is determined by the culture of freeze-dried probiotic raw material in the laboratory. When incubated in a nutrient-rich substrate, probiotics tend to form “colonies”. These colonies are counted after 72 hours of incubation and multiplied by a dilution factor to obtain the number of Colony Forming Units or CFUs. In one serving of a probiotic supplement, there are typically billions of live probiotic bacteria, which is noted on our labels as “billion CFU.”

Stability

Temperature plays an important role in the stability of probiotics. High heat can degrade the viability of these organisms. Even under ideal storage conditions, the number of colony-forming units (CFUs) will gradually decline over time. Refrigeration can prolong the potency and viability of most probiotics, maintaining higher counts (CFUs) over a more extended period. The colder air holds less moisture and is not within the ideal temperature range for bacteria to commonly grow and thrive, thus inhibiting the reactivation of dormant organisms by depriving them of the warmth and moisture that represent their ideal growing conditions. Adding freshness packets in bottles to help absorb and reduce moisture is another way to enhance probiotic stability.

Maintaining Potency

The rate of decline in viable CFU numbers can increase if a probiotic product is stored in excessively warm or moist conditions, especially after opening, when moisture can move easily into the package. Due to the extreme variability of seasonal weather and environmental conditions that a product may encounter, as well as the duration of these exposures, it's difficult to accurately predict potency and shelf life for every individual's situation across a wide geographical area. Our products are formulated to deliver the potency indicated on the label through the best-by date when they are stored properly. Each of our probiotic products has suggested storage information on the label.

Refrigeration after opening is usually ideal for storing probiotics. But if that is not possible, it is best to keep the package in a cool, dry place to maintain good stability. Unfortunately, many people tend to keep their supplements in the kitchen or bathroom, which are notorious for being warm and moist and known to shorten the shelf life of many kinds of supplements. Those conditions are ideal for bacterial and mold growth, which means that the probiotics will initially tend to activate but then die off more quickly than expected, as they are not yet in the human body where they can live, grow, and thrive. In these adverse conditions, probiotics may lose potency more rapidly than anticipated. CFU counts are calculated based on storage in a cool, dry place. Refrigerating probiotic products will enhance viability and shelf life.

Testing

To meet label claims for probiotics, manufacturers, including NOW, will generally add an overage to account for the natural decline in CFUs over time. Finished products are tested from the time of manufacture and at various time intervals throughout their shelf life. Monitoring the die-off rate helps determine the amount of overage needed to maintain potency at the end of shelf life. Real-time stability studies, conducted under various storage conditions and with different packaging materials as required, are also performed to generate data for calculating an experimental stability curve. The stability curve predicts changing CFU counts throughout the product's shelf life in a controlled environment. 

NOW tests the stability of their probiotic products during transport. Based on the testing results, a sealed probiotic formula exposed to a temperature of over 122°F for 24 hours will still meet the CFU label claim. These results indicate that the level of heat over that time was insufficient to kill many of the organisms in the package. It also shows that the overage added to counter the die-off of the probiotics is sufficient to meet the label claim. It would take even harsher conditions to rapidly degrade the potency of this specific probiotic product. There is evidence that the stability of freeze-dried probiotics is greater, and the organisms are more resistant to heat. 

The stability of a probiotic formula, as tested at the time of manufacture, will depend on a combination of factors. Variations in packaging, temperature, and humidity will affect the viability of probiotic products. Protective factors that help preserve the freshness and viability of probiotic strains in a supplement include resistant packaging and storage in a cool, dry place, ideally in refrigerated or freezing conditions.