Probiotic storage checklist: heat, humidity and holiday travel

Over the holidays, a bottle of probiotics can have a rough week. It might sit on a steamy bathroom shelf, ride in a suitcase, or end up on the counter next to an oven that's been on all day.

Probiotics are live microbes, so the way you store them affects how many are still alive when you take them. The good news is that a few simple habits cover most of the risk. Here's what the research says, followed by checklists for home and travel.

What shortens a probiotic's life

For dried probiotics in capsules or powders, moisture is a major factor. In a long-term storage study, researchers kept a dried probiotic strain, Lactobacillus rhamnosus GG, at room temperature for up to 14 months at three levels of available water. At the highest level, viability dropped rapidly. At the middle level, counts fell by 2.4 log units, which means more than 99% of the bacteria were lost. At the driest level, the drop was only 0.29 log units, or roughly half (Vesterlund et al., 2012).

A second lab study found the same pattern in spray-dried probiotic powders and four commercial supplements kept at room temperature: the more water available in the product, the lower the survival of the bacteria (Dianawati et al., 2016).

Temperature matters too, and it depends on the product. Traditional probiotic foods like yogurt need refrigeration and have a short shelf life, while dried supplements are often formulated to stay stable for up to 24 months at room temperature and humidity (Fenster et al., 2019). That's why your label, not a general rule, is the best guide.

The at-home checklist

• Follow the label first. If it says refrigerate, refrigerate. If it gives a temperature limit, take it seriously.
• Keep it out of the bathroom. Hot showers make it one of the most humid rooms in the house.
• Skip spots near the stove, kettle, dishwasher and sunny windowsills. Heat and steam add up over weeks.
• Keep it in the original container. If there's a desiccant packet inside, leave it there.
• Close the lid right away. Every minute it's open lets in room air and its moisture.
• Use dry hands. Don't reach in with damp fingers or put a wet scoop back into a powder.
• Check the date. Look for a count guaranteed through expiration, and finish the bottle before that date.

The holiday travel checklist

• Pack it in your carry-on. That way it stays with you, and you know where it's been.
• Bring the original bottle if you can. If you prefer a pill organizer, fill only a few days' worth and keep it closed and dry.
• Refrigerated product? Ask the manufacturer how long it can safely be out of the fridge. Use an insulated bag with a cold pack if needed, and keep the bottle away from melting ice and condensation.
• Don't leave it in a parked car. Cars can heat up in the sun, even on a cool day.
• Anchor the timing. Time zones and holiday meals scramble routines. Tie your dose to something you'll still do every day, like your first cup of coffee.
• If you miss a day, don't double up. Just pick your routine back up, unless your label says otherwise.

Refrigerated or shelf-stable: is one better?

Not automatically. Refrigeration is the traditional way to keep probiotic foods like yogurt alive. Many dried supplements, by contrast, are designed for room-temperature storage, and the review above notes that the right production process, formulation and strains can make probiotics work in a wide range of formats (Fenster et al., 2019).

What matters is whether a product is kept the way it was designed and tested to be kept. A shelf-stable capsule that lives in a steamy bathroom may fare worse than one in a cool, dry cupboard. A refrigerated product left on the counter for days no longer has the conditions its label assumes. So the useful question isn't "fridge or no fridge?" It's "Am I following this label?"

Signs a bottle may be past its best

• Capsules that are sticky, clumped or discolored
• Powder that has hardened or caked, a hint that moisture got in
• A bottle that spent a long stretch somewhere hot or humid
• A product past its expiration date

You can't count live microbes at home, so none of these signs proves anything. They're simply a good reason to replace the bottle or contact the company.

When storage isn't the problem

If you've stored a probiotic well and taken it consistently for two to three months without any change, the fridge probably isn't the issue. The strain may just not be a good fit for your gut. Here's how to judge a fair trial.

And if the holidays bring symptoms that don't settle, such as blood in your stool, unexplained weight loss, or new bloating that happens most days, especially with early fullness or pelvic pain, check in with your doctor rather than changing supplements.

Sources

1. Vesterlund S, Salminen K, Salminen S. Water activity in dry foods containing live probiotic bacteria should be carefully considered: a case study with Lactobacillus rhamnosus GG in flaxseed. Int J Food Microbiol. 2012;157(2):319-21. PMID 22663981
2. Dianawati D, Mishra V, Shah NP. Viability, acid and bile tolerance of spray dried probiotic bacteria and some commercial probiotic supplement products kept at room temperature. J Food Sci. 2016;81(6):M1472-9. PMID 27145163
3. Fenster K, Freeburg B, Hollard C, Wong C, Rønhave Laursen R, Ouwehand AC. The production and delivery of probiotics: a review of a practical approach. Microorganisms. 2019;7(3):83. PMID 30884906

This article is for general information and isn't medical advice. Follow the storage directions on your product's label, and talk to your healthcare provider about symptoms that are new, persistent or worrying.