One clinical study offered kefir to breast cancer patients who had received chemotherapy and/or radiation within the past 2 years and found that the patients’ Beck depression inventory, total piper fatigue score, gastric distress score, intermediate monocytes, and IL-6 levels decreased significantly (p < 0.05), suggesting an improvement in the health status of patients (Smoak et al., 2021). Here, IL6 is linked to breast cancer.