Is Miso a Probiotic?

If you’ve ever swirled a spoonful of miso into a bowl of warm soup, you’ve tasted the earthy depth that fermented soybeans bring. But is miso a probiotic?

Probiotics are live microorganisms found in fermented foods that can support digestive health. They help balance the gut microbiome, potentially boosting immunity, aiding digestion, and maybe even improving your mood.

Traditionally fermented miso, made with koji (Aspergillus oryzae), soybeans, and salt, is naturally rich in these beneficial microbes. Living organisms like koji, lactic acid bacteria, and yeasts thrive during fermentation—turning miso into a probiotic powerhouse.

Here’s the catch: some misos are pasteurized to extend shelf life, which kills off those helpful bacteria. If you’re choosing miso for gut health, look for unpasteurized varieties. All of the products in our Organic Miso series are unpasteurized and retain their live cultures.

Regardless of pasteurization, miso is also packed with prebiotic compounds, especially oligosaccharides, which feed the good bacteria already in your gut. That makes miso a rare synbiotic—delivering both probiotics and the nourishment they need to thrive.And remember, for the full benefit of miso, don’t boil it. Heat destroys those fragile microbes. Instead, stir miso into the soup after removing it from the heat, or use it in dressings, dips, and marinades where its savory, umami-rich flavor can truly shine. For more practical tips on using miso, see How to Use Miso.