Selenium yeast is sometimes used as a supportive supplement during chemotherapy due to its antioxidant properties and its role in maintaining immune function. Scientific interest in selenium, including selenium yeast (an organic form of selenium), arises from its ability to be incorporated into selenoproteins that help protect cells from oxidative damage—a major source of chemotherapy side effects. Several small clinical trials and observational studies have explored selenium supplementation in cancer patients, mostly in the context of reducing chemotherapy-induced toxicity, particularly in head and neck, gynecological, and colorectal cancers.

The evidence, however, is mixed and limited. Some studies (e.g., Muecke et al., 2010, Trace Elements and Electrolytes) report reduced rates of chemotherapy-induced diarrhea and improved white blood cell counts with selenium yeast supplementation. Other randomized controlled trials suggest possible reductions in oral mucositis and nephrotoxicity. However, the sample sizes in these studies are often small, and results are not universally reproduced. Major cancer organizations do not routinely recommend selenium supplementation during chemotherapy due to insufficient high-quality evidence and concerns about potential interactions with cancer therapies.

In summary, there is preliminary scientific evidence suggesting selenium yeast may reduce some chemotherapy side effects, but the overall quality and consistency of the data are low. More robust, large-scale randomized trials are needed to confirm any clinical benefit and establish safety guidelines.