Do probiotics go bad in heat? A comprehensive guide to viability and storage

October 11, 2025 •

4 min read

Many probiotic strains are sensitive to heat and moisture, which can degrade their viability and effectiveness. So, do probiotics go bad in heat? The answer depends on the specific product, but high temperatures can certainly compromise their live cultures if not stored correctly. This guide will explain how heat impacts probiotics and what you can do to ensure you’re getting the most potent supplement possible.

Quick Summary

Probiotic viability is vulnerable to heat, leading to decreased potency. Storage requirements vary by product, from refrigeration to special shelf-stable options that use protective processing and packaging, such as freeze-drying.

Key Points

Heat degrades probiotic viability: High temperatures kill the live bacteria in most probiotic supplements, causing them to lose potency over time.
Storage depends on the product type: Some probiotics are refrigerated due to sensitive strains, while others are shelf-stable because they use hardy strains or are freeze-dried.
Follow label instructions carefully: Always check the label for specific storage requirements, as incorrect storage can render the supplement ineffective.
Packaging is crucial: Moisture-resistant packaging and special coatings protect shelf-stable probiotics from premature degradation.
Heat-killed probiotics can still be beneficial: Even dead probiotics can offer immunomodulatory benefits, though they cannot colonize the gut.
Avoid hot, humid locations: Never store probiotics in your car, a humid bathroom, or near heat sources, as this can accelerate bacterial death.

The enemies of probiotic viability: Heat, light, and moisture

For probiotics to deliver their intended health benefits, the beneficial microorganisms they contain must remain alive and viable from the time of manufacturing until they reach your gut. Unfortunately, these tiny organisms are quite delicate and are susceptible to a variety of environmental factors that can reduce their potency over time. The three main culprits are heat, moisture, and light.

Heat: High temperatures accelerate the death of probiotic bacteria. Most probiotics are not designed to withstand temperatures above 70°F (21°C) for prolonged periods. Some, particularly in fermented foods like yogurt, can be killed at temperatures above 115°F (46°C). This is why leaving a refrigerated probiotic supplement in a hot car or a warm, humid bathroom can drastically reduce its effectiveness.
Moisture: Probiotics are often freeze-dried to put them in a dormant, shelf-stable state. The presence of moisture can reactivate them prematurely within the capsule or sachet. This premature activation, away from the gut, can cause them to die off more quickly and lose their beneficial effects.
Light: Direct sunlight and UV rays can also degrade and damage the live bacteria in probiotics. This is why proper packaging is crucial for protecting the supplement from external factors.

The two types of probiotic products: Shelf-stable vs. refrigerated

It's a common misconception that all probiotics must be refrigerated. The storage instructions depend entirely on the specific strains used and the manufacturing process.

Refrigerated probiotics

These products contain strains that are more sensitive to temperature and environmental changes. They must be kept cold to maintain the bacteria in a viable state. This category often includes liquid probiotics, dairy products like yogurt and kefir, and specific supplements featuring delicate strains like certain Lactobacillus or Bifidobacterium species. If a probiotic is stored in the refrigerated section at the store or shipped with ice packs, it needs to be refrigerated upon arrival.

Shelf-stable probiotics

These are formulated to withstand room temperature, making them more convenient for travel and daily use. Manufacturers achieve this stability in several ways:

Freeze-Drying: This process puts the bacteria into a dormant, suspended state, which is less susceptible to environmental damage.
Hardy Strains: Some probiotic strains, such as spore-forming Bacillus, are naturally more resistant to heat, acid, and bile.
Protective Packaging: Moisture-resistant vials, special capsule coatings, and blister packs help protect the contents from moisture and heat.

Comparison of refrigerated vs. shelf-stable probiotics


Feature	Refrigerated Probiotics	Shelf-Stable Probiotics
Viability	Can have higher live counts if handled correctly.	Manufactured to remain viable at room temperature until expiration.
Convenience	Less convenient due to constant refrigeration needs.	Highly convenient for travel and daily use.
Cost	Often more expensive due to specialized cold chain handling.	Generally more affordable and cost-effective.
Strains	Often contains more sensitive, delicate strains.	Uses hardier, more resilient strains, or freeze-dried versions.
Effectiveness	Not necessarily superior; effectiveness depends on the right strain for the right purpose.	Just as effective as refrigerated versions if the strain and dosage are appropriate.

The emerging role of heat-killed probiotics

An interesting development in probiotic science is the study of heat-killed probiotics, also known as paraprobiotics. While a long-held belief was that probiotics must be alive to be effective, research now shows that even heat-inactivated bacteria can provide significant health benefits. These benefits stem from the components released by the dead cells, such as lipoteichoic acids, peptidoglycans, and exopolysaccharides.

Benefits of heat-killed probiotics include:

Immunomodulation: Can have powerful effects on the immune system, sometimes even more effectively than live strains in certain contexts.
Increased Safety: Pose no risk of infection for individuals with severely compromised immune systems, for whom live bacteria might be a concern.
Superior Stability: Can withstand harsh manufacturing conditions, high temperatures, and have a much longer shelf life, making them ideal for feed additives and certain supplements.

However, it's crucial to understand that heat-killed probiotics cannot colonize the gut or replicate. Their effects are based on the bioactive compounds released, not on establishing a permanent presence in the microbiome. For most consumers seeking general gut health support, traditional live probiotics are still the focus, but research into paraprobiotics is expanding our understanding of how these beneficial microbes work.

How to maximize the potency and life of your probiotics

To ensure your probiotics remain as potent as possible, follow these best practices:

Read the Label: Always check the label for specific storage instructions. If it says "Refrigerate," do so.
Maintain Consistent Temperature: Store refrigerated probiotics in the main compartment of the fridge, away from the door where temperatures fluctuate more.
Avoid Humidity: Keep shelf-stable probiotics in a cool, dry place, like a cabinet or pantry, not the bathroom.
Keep in Original Packaging: The manufacturer's packaging is designed to protect the cultures from moisture and light. Avoid transferring them to weekly pill containers.
Look for Guaranteed Potency: Choose products that guarantee a certain number of Colony Forming Units (CFUs) through the expiration date, not just at the time of manufacture.

Conclusion: The heat is on, so store them right

Yes, do probiotics go bad in heat, and the extent of the damage depends on the strain, formulation, and duration of exposure. High temperatures can kill off the live cultures that make these supplements effective, potentially rendering your investment useless. However, modern advancements in manufacturing and packaging have led to a wide range of reliable shelf-stable options for those who prefer convenience. Always check the label for specific storage recommendations and follow them closely to ensure the live microorganisms remain viable. Furthermore, the rising interest in heat-killed probiotics shows that even non-viable bacteria can provide significant health benefits, though their mechanism of action differs from that of live cultures. Ultimately, being mindful of your probiotic's needs will help you maximize its potency and support your gut health goals.

Frequently Asked Questions

The exact temperature varies by strain, but most live probiotic bacteria are susceptible to temperatures above 70°F (21°C). Many can be killed by temperatures above 115°F (46°C). Consistent exposure to heat, even at lower temperatures, will degrade their viability over time.

If you forget to refrigerate a refrigerated probiotic for a short period (e.g., a few hours), it will likely retain some viability. However, for longer periods, especially in warm conditions, a significant portion of the bacteria may die off. For safety and guaranteed potency, it's best to discard any refrigerated probiotics left out for more than 24 hours.

No, shelf-stable probiotics are not inherently less effective than refrigerated ones. Their stability is achieved through advanced manufacturing techniques like freeze-drying and the use of hardier strains. The key is to choose a product that uses clinically studied strains and guarantees its CFU count through the expiration date, regardless of its storage requirements.

Signs of a compromised probiotic include a decline in the benefits you typically experience (e.g., persistent digestive issues), an unusual smell, or physical changes like clumping in the powder or capsules. If you notice these issues, or if the product was stored improperly, its potency is likely compromised.

Yes, but how you travel depends on the product. For refrigerated probiotics, use an insulated bag with an ice pack. Shelf-stable probiotics are ideal for travel, as they are designed to withstand room temperature. Always keep them in their original, moisture-proof packaging.

Yes. Probiotic foods like yogurt, kefir, and sauerkraut rely on live and active cultures to provide benefits. They must be refrigerated, as the bacteria are not only sensitive to heat but also the food itself can spoil. Exposing these foods to heat will kill the live cultures.

Heat-killed probiotics, or paraprobiotics, are microorganisms that have been intentionally inactivated with heat. Research shows they can still offer health benefits, such as immunomodulatory effects, even without being alive. They are more stable and safer for immunocompromised individuals but do not colonize the gut.