Probiotics are live microorganisms that, when administered in adequate amounts, are intended to confer a health benefit on the host. The efficacy of these supplements relies entirely on the number of viable organisms, measured in Colony-Forming Units (CFUs), that survive until consumption. Because these living microbes are sensitive to external conditions, proper storage is essential for maintaining viability and receiving the intended health benefits.
Temperature Requirements for Preservation
Temperature is the primary factor dictating the stability and shelf life of probiotic bacteria. The specific strains used determine whether a product requires refrigeration or can be stored at ambient room temperature. If a product is labeled for refrigeration, it should be kept consistently between 35°F and 40°F (2°C to 4°C) to slow the degradation of the live cultures.
Many modern probiotic supplements are now considered “shelf-stable” and do not require constant chilling. This stability is often achieved through lyophilization (freeze-drying), which removes moisture and puts the bacteria into a dormant state. While resilient, they should still be kept in a cool location, typically below 77°F (25°C). Exposure to heat spikes, such as being left in a hot car, can rapidly compromise the viability of both refrigerated and shelf-stable varieties.
Refrigerated probiotics are sensitive, with potency beginning to decline rapidly if they are left out at room temperature for an extended period. Repeated temperature fluctuations, such as frequently moving them in and out of the refrigerator, should be avoided to maintain a consistent environment. Cooler storage can sometimes extend the potency of shelf-stable probiotics beyond the guaranteed expiration date.
Protecting Probiotics from Environmental Damage
Beyond temperature, the viability of live cultures is continually threatened by moisture, oxygen, and light exposure. High humidity is particularly detrimental because it can prematurely activate the dormant, freeze-dried bacteria, causing them to degrade quickly. Probiotic bacteria often do not thrive in the presence of oxygen, which can cause cellular damage.
To combat these threats, packaging integrity is important. Manufacturers use tightly sealed, opaque containers or blister packs designed to create a barrier against light and moisture ingress. Many bottles include desiccant packets, which are small pouches of moisture-absorbing material, to maintain a low-humidity environment.
Consumers should always keep supplements in their original packaging, as it is engineered for protection against environmental stressors. Storing probiotics in high-humidity areas, such as a bathroom cabinet or near a kitchen sink, is strongly discouraged. Once a bottle is opened, the seal is broken, making it important to close the cap tightly immediately after use to minimize oxygen and moisture exposure.
Assessing Shelf Life and Potency
The potency of a probiotic is quantified by its Colony-Forming Units (CFU) per serving. When evaluating a product, check the label to see if the CFU count is guaranteed “at time of manufacture” or “through expiration.” A guarantee “through expiration” is more reliable, as it confirms the stated dose will remain viable until the best-by date, assuming proper storage.
For refrigerated products, short-term transport requires careful management to prevent a rapid decline in potency. When traveling, users should place the product in an insulated container with a cold pack to maintain the recommended temperature range. Avoid placing the probiotics in direct contact with the cold pack, as freezing can kill the bacteria and generate damaging moisture through condensation.
If a refrigerated product must be out of the fridge, many formulations can maintain stability for a week or more at ambient temperatures. If a product has passed its expiration date, its potency will rapidly decline, even if stored correctly. While consuming expired probiotics is generally not unsafe, the reduced number of live cultures means the supplement may no longer deliver its intended health benefits.