Dr. Johnston looks at a 2026 phase II study in which 40 patients with advanced lung cancer or melanoma received donor gut bacteria in capsules before immunotherapy, and a 2026 analysis of 105 studies on probiotic use during immunotherapy. The phase II study was small, and the larger analysis reports associations rather than proof of cause.
Can improving the bacteria in your gut actually improve cancer treatment? The microcosmos is an incredible wonder, as diverse and beautiful under the microscope as the galaxy is under our strongest telescopes. Truly indescribable.
As Ant-Man said in Avengers: Endgame, "I was in a place called the quantum realm. The quantum realm was like its own microscopic universe. To get in there, you have to be incredibly small." Now, we're not quite going that small, but this is an example of the organisms we take for granted, which live inside our bodies. We are their universe, and they depend on us as much as we depend on them.
Yogurt and kefir are two natural foods which are filled with healthy probiotics. Also kombucha, a popular drink, and fermented sauerkraut.
Let's look at a remarkable phase two study on probiotic organisms and cancer. In January 2026, a study was published by Nature Medicine. Researchers took 40 patients with advanced cancer, 20 with lung cancer and 20 with melanoma. Before starting immunotherapy, each patient received carefully screened healthy donor gut bacteria in capsules. 16 of the 20 lung cancer patients responded positively to treatment. That's 80%. Typical immunotherapy response rates in lung cancer average 20 to 45%. And 15 of the 20 melanoma patients responded positively. That's 75%. Typical immunotherapy response rates in melanoma average 40 to 45%.
But this is not just one isolated experiment. A 2026 analysis looked at 105 studies involving more than 77,000 patients with cancer receiving immunotherapy. Probiotic use was associated with a 95% higher chance of responding to immunotherapy positively, plus a 44% lower hazard of death.
But when it comes to cancer research, which bacteria are present matter. Published human studies have linked specific gut bacteria with better outcomes, particularly in patients receiving immunotherapy. First up is Bifidobacterium longum, and Bifidobacterium, Akkermansia and Lactobacillus salivarius.
Here's the research. You decide.
Educational research summary, not medical advice. Talk with your oncologist and pharmacist before starting, stopping or changing any treatment or supplement.