You can get probiotics from two main sources: fermented foods and dietary supplements. Fermented foods are the most accessible starting point, and for most people, a few daily servings of probiotic-rich foods provide meaningful amounts of beneficial bacteria without the cost or complexity of supplements.
Fermented Foods With Live Cultures
Fermented foods contain probiotics naturally because bacteria or yeast drive the fermentation process, and many of those microorganisms survive in the final product. The key phrase to look for on packaging is “live active cultures,” which confirms the beneficial bacteria haven’t been killed off by heat processing or pasteurization.
The most widely available probiotic foods include:
- Yogurt and kefir (dairy or non-dairy versions made from soy, coconut, or water)
- Sauerkraut and kimchi (choose refrigerated, unpasteurized varieties)
- Miso and tamari
- Tempeh
- Kombucha
- Aged cheese, cottage cheese, and sour cream
- Buttermilk and acidophilus milk
Not all versions of these foods contain live probiotics. Sauerkraut sold in shelf-stable jars, for instance, has typically been heat-pasteurized, which kills the bacteria. The same goes for pickles made with vinegar rather than through natural fermentation. Look for products in the refrigerated section that specifically mention live cultures on the label. Yogurt is the easiest entry point since nearly all major brands in the refrigerated aisle contain active cultures, and the label will say so.
Feed Your Probiotics With Prebiotics
Probiotics need fuel to thrive once they reach your gut. That fuel comes from prebiotics, which are specific types of fiber that your body can’t digest but your gut bacteria can. Eating prebiotic-rich foods alongside probiotic foods creates a more hospitable environment for beneficial bacteria to colonize and multiply.
The foods with the highest prebiotic content are dandelion greens, Jerusalem artichokes, garlic, leeks, and onions, which contain roughly 100 to 240 milligrams of prebiotics per gram of food. Asparagus, cowpeas, and onion rings also rank well at around 50 to 60 mg/g. The International Scientific Association for Probiotics and Prebiotics recommends about 5 grams of prebiotics per day. To hit that target, you’d need to eat roughly half of a small onion, which is easy to work into a stir-fry, soup, or salad. Garlic and leeks in everyday cooking count too.
When Supplements Make Sense
Probiotic supplements are worth considering if you don’t eat fermented foods regularly, if you’re targeting a specific health concern, or if you want a more consistent daily dose. Most supplements contain between 1 billion and 10 billion colony-forming units (CFUs) per dose, though some products go as high as 50 billion or more. Higher CFU counts are not necessarily more effective than lower ones, so more isn’t automatically better.
The specific strain matters more than the total count. Probiotic benefits are strain-specific, meaning a bacterium that helps with one condition may do nothing for another. A quality supplement label should list the genus, species, and strain for each organism in the product. If a label only says something vague like “probiotic blend” without naming strains, that’s a red flag.
How to Read a Supplement Label
Probiotic supplements aren’t regulated as strictly as prescription drugs, so label quality varies. Industry best practices call for the CFU count on a label to reflect the number of live organisms at the end of the product’s shelf life, not at the time of manufacture. This distinction matters because bacteria die over time. A product labeled at the time of manufacture could contain far fewer live organisms by the time you take it. Look for language on the label or manufacturer’s website that specifies “at time of expiration” or “through end of shelf life.”
Third-party testing seals from organizations like USP, NSF, or ConsumerLab provide an extra layer of confidence that the product actually contains what it claims.
Refrigerated vs. Shelf-Stable Products
Whether a probiotic needs refrigeration depends on its form. Probiotic foods like yogurt, kefir, and fermented milks rely on cold temperatures (and in some cases, acidity) to keep bacteria in a dormant state. These always need refrigeration.
Supplements work differently. Many capsules and tablets contain bacteria that have been freeze-dried through a process called lyophilization. The cells are first frozen at extremely low temperatures, then the water is gently removed, leaving the microbes in a hibernation-like state with no growth, reproduction, or metabolic activity. These shelf-stable supplements don’t need refrigeration because the bacteria are already dormant and will reactivate when they encounter moisture in your digestive tract. That said, some supplement brands still recommend refrigeration to extend potency. Check the label for storage instructions and follow them.
Side Effects and Who Should Be Cautious
Most healthy people tolerate probiotics well. The most common initial side effects are gas and bloating, which typically fade within a few days to a week as your gut adjusts. Starting with a lower dose or a single serving of fermented food and gradually increasing can help minimize discomfort.
The risks increase for people with severely compromised immune systems or critical illness. Cases of serious infections have occurred in premature infants given probiotics, and the FDA has warned healthcare providers about this specific risk. People who are very weak or immunocompromised should discuss probiotics with their doctor before starting. For everyone else, taking probiotics alongside antibiotics appears to be safe based on available evidence.
One broader concern is the potential for probiotic organisms to transfer antibiotic resistance genes to other bacteria in the digestive tract. Research on this is still limited, but it’s another reason to choose well-tested strains from reputable manufacturers rather than grabbing the cheapest option on the shelf.
A Practical Starting Plan
The simplest approach is to build fermented foods into meals you already eat. A cup of yogurt or kefir at breakfast, kimchi or sauerkraut as a side at lunch or dinner, and a miso-based dressing or soup a few times a week will expose your gut to a diverse mix of beneficial bacteria. Pair those with prebiotic-rich foods like garlic, onions, and leeks, which are already common in most cooking.
If you add a supplement, choose one with clearly labeled strains, a CFU count guaranteed through expiration, and storage instructions you can realistically follow. Start with a product in the 1 to 10 billion CFU range and see how your body responds before considering higher doses.