Do probiotics need to be refrigerated?

"Do probiotics need to be refrigerated?" has a genuinely strain-dependent answer, and the experts are careful about it. Attia (with guest Michael Gershon) notes that refrigeration isn't universally required — some strains, like Saccharomyces-based yeasts, are hardy enough to survive stomach acid without it, and Hyman points to spore-based Bacillus probiotics that are validated as shelf-stable. On the other hand, many common Lactobacillus and Bifidobacterium products degrade at room temperature, which is why they're sold refrigerated and why Huberman tells people to choose live-culture products from the refrigerated section.

But the panel's more important message is that you're asking a second-order question. The CFU (colony-forming units) number that dominates probiotic marketing is, in Attia's words, a weak and largely unregulated metric — labels often list CFU at the time of manufacture, not at expiration, and the freeze-drying used to make the powder already kills a large fraction of the cells. Hyman agrees that strain specificity and storage matter more than a big CFU number, and that a quality probiotic has to actually be alive (verified potency on arrival) and third-party tested. Patrick adds that probiotics may not permanently colonize your gut and that pills are limited by low doses and by surviving stomach acid.

So what should you do? For general gut health, Huberman's top recommendation isn't a pill at all — it's 4 servings a day of low-sugar fermented foods with live active cultures (from the refrigerated section, not the shelf-stable canned versions), a practice backed by a Stanford (Sonnenburg) study that both he and Patrick cite for increasing microbial diversity and lowering inflammation. If you do want a supplement — say, a specific clinically studied strain for a specific problem — then pick a third-party- or USP-validated brand, check that potency is guaranteed through expiration (not just at manufacture), and match the refrigeration to the strain.