Probiotics help promote digestive health, boost your immune system, and can even be good for your mental health. Not too bad for bacteria, right? So, if you’ve been trying to zero in on which probiotics are best for you, you might be curious: Why are some probiotic supplements shelf-stable while others need to be stored in your refrigerator? And is one type better than the other when it comes to achieving your health goals? We’ll let the experts take it from here. 

What Does It Mean If A Probiotic Needs To Be Refrigerated? 

First things first: Probiotics are living organisms that are taken in supplement form to boost the presence of healthy bacteria in the gut, explains Dr. Josh Axe, D.C., D.N.M., C.N.S., co-founder of Ancient Nutrition and member of The Vitamin Shoppe Wellness Council.

Because the bacteria are living, they need to survive in the supplement bottle until they are consumed and ultimately reach the gut. Factors such as room temperature and moisture content impact the survival rates of certain bacteria strains, which is why some products need to be kept in the fridge. “Simply put, some probiotics need to be refrigerated because the strain of bacteria being used in the supplement is more sensitive to environmental factors, such as heat, and may degrade faster when not kept in cool temperatures,” Axe explains. 

Read More: Should You Rotate Probiotic Supplements?

As for the products that are a-okay to be stashed on shelves? They’re often made with bacteria strains that can endure harsher environments—and those bacteria may have been freeze-dried during production or wrapped up in heat- and moisture-resistant packaging, Axe says.

For example, research shows that Lactobacillus paracasei can survive at the low temperatures that freeze-drying requires. However, Lactobacillus delbrueckii doesn’t hold up to temps below 32 degrees Fahrenheit, so would lose effectiveness in a freeze-drying process. So, you may be more likely to see the former in shelf-stable products.

How To Store Your Probiotics

If this has you guessing whether you should be stashing your probiotics in the fridge or the pantry, well, don’t read into it too much.

A probiotic that needs to be refrigerated will clearly say as much on its label, Axe says. Plus, you’ll find it in a refrigerator at the store you purchase it from. The shelf-stable probiotics, meanwhile, will be found on store shelves with other supplements. When in doubt, you can always refer to the label for specific storage instructions, he notes. A good place to stash that must-be-refrigerated probiotic supplement? Right next to foods that contain living probiotics, like yogurt.

Also worth noting: Probiotics are some of the most sensitive dietary supplements, according to dietitian Wendy Lord, R.D., a contributor to the health professional network Health Reporter. This means that even the shelf-stable ones should be stored carefully according to their directions. Because they’re so sensitive to environmental factors like sunlight, oxygen, and moisture, their packaging is intentional, so you shouldn’t transfer them to a plastic bag to tote around with you or store them in, say, a medicine cabinet in your bathroom that might get steamy.

Regardless of whether your probiotics are refrigerated or shelf-stable, they should have an expiration date marked on the package that you’ll want to keep in mind, notes Lord. Generally speaking, most probiotics should be used within one year of purchase, adds nutrition consultant Dr. Nicole Avena, Ph.D., an associate professor at Mount Sinai School of Medicine. Even with refrigeration, probiotics tend to lose about 10 percent of their potency every month you have them.

So, Should You Opt For shelf-stable or Refrigerated Probiotics?

If you’re wondering whether you should stick with your shelf-stable probiotic or make the switch to refrigerated probiotics, know this: One isn’t necessarily better than the other! While it might seem that refrigerated products are more likely to retain their potency than shelf-stable options, there’s plenty of technology nowadays that protects the bacteria in shelf-stable products from heat, light, and oxygen, Lord says. 

Which you choose really comes down to personal preference (are you likely to forget your probiotic if it’s tucked away in the fridge?) and whether your healthcare provider has recommended you take certain strains in order to support your unique health needs and goals, she says.

Read More: 9 Groups Of People Who Need More Probiotics

Ultimately, “neither choice is superior, so any type of high-quality probiotic will be beneficial,” Lord says.

As for what “high-quality” looks like, you’ll want to look for two things: a variety of different types of probiotics and enough of them. “Diversity is the key when it comes to probiotics,” explains Lord. “The gut flora is diverse, so supplements should have a variety of bacterial strains as well.” Some of the most-researched strains are Lactobacillus, Bifidobacterium, Bacillus, and Saccharomyces boulardii. And when it comes to quantity, pay attention to the number of colony-forming units, or CFUs, on the label. It’s generally recommended to choose probiotic products with at least 1 billion colony-forming units, according to the Cleveland Clinic. (The Vitamin Shoppe Ultimate 10+ Probiotic contains 50 billion CFUs.)

No matter which type of probiotic supplement you choose, the real ticket is to make sure you store it properly so you can reap the most health benefits.