You are right that the evidence-base for many practices has based on a limited demographic; although in recent years the evidence has improved in response to demands from individuals like yourself and funding agencies. Funded studies are now often required to include and then report results from diverse groups in terms of gender, age, race, and ethnicity.
If your clinic practices measurement based care, which we strongly recommend, then you can help to further specify the evidence-base. Additionally, practicing measurement based care will provide data to decide best practices for a particular individual patient. Measurement based care is routine objective measurement of a domain (e.g., symptoms, side effects, quality of life) and then using those data on an ongoing basis to adjust treatment. Your decisions about outcomes to track as part of measurement based care may also be influenced by cultural factors and patient preferences.