This site lists three sources: two PubMed searches and one NIH fact sheet.
What they are
- PubMed: berberine and glycemic control (meta-analysis search)
- PubMed: Gymnema Sylvestre and glycemic control
- NIH Office of Dietary Supplements: chromium fact sheet
What they don't cover
There is no source for Cinnamon Bark, and none tests the finished GlucoPril product. The first two are search-result links, so they point you to studies rather than to one study.
💡 This is general educational information, not personalized medical advice.