A novel dietary index for gut microbiota (DI-GM) was developed and evaluated based on a systematic review of 106 articles. The DI-GM includes 14 foods or nutrients: beneficial components such as fermented dairy, chickpeas, soybean, whole grains, fiber, cranberries, avocados, broccoli, coffee, and green tea; and unfavorable components such as red meat, processed meat, refined grains, and a high-fat diet (≥40% of energy from fat). The DI-GM was calculated using dietary data from the National Health and Nutrition Examination Survey (NHANES), with scores ranging from 0 to 13, and a mean of 4.8. The DI-GM was positively associated with urinary enterodiol and enterolactone, which are indirect biomarkers of gut microbiota diversity. The DI-GM showed moderate correlations with existing dietary indices such as the Healthy Eating Index (HEI-2015) and the Mediterranean Diet Score (MDS). The DI-GM demonstrated a positive association with gut microbiota diversity, indicating its potential utility in gut health-related studies. The study highlights the importance of diet in shaping gut microbiota and provides a tool for assessing dietary patterns related to gut health. The DI-GM is a literature-based index that can be used to evaluate the impact of diet on gut microbiota diversity and health.A novel dietary index for gut microbiota (DI-GM) was developed and evaluated based on a systematic review of 106 articles. The DI-GM includes 14 foods or nutrients: beneficial components such as fermented dairy, chickpeas, soybean, whole grains, fiber, cranberries, avocados, broccoli, coffee, and green tea; and unfavorable components such as red meat, processed meat, refined grains, and a high-fat diet (≥40% of energy from fat). The DI-GM was calculated using dietary data from the National Health and Nutrition Examination Survey (NHANES), with scores ranging from 0 to 13, and a mean of 4.8. The DI-GM was positively associated with urinary enterodiol and enterolactone, which are indirect biomarkers of gut microbiota diversity. The DI-GM showed moderate correlations with existing dietary indices such as the Healthy Eating Index (HEI-2015) and the Mediterranean Diet Score (MDS). The DI-GM demonstrated a positive association with gut microbiota diversity, indicating its potential utility in gut health-related studies. The study highlights the importance of diet in shaping gut microbiota and provides a tool for assessing dietary patterns related to gut health. The DI-GM is a literature-based index that can be used to evaluate the impact of diet on gut microbiota diversity and health.