A lot has been published over the years of the potential benefits of rutin, a flavonoid, as a supportive treatment in diabetes which may not only lower blood sugar, but also combat the complications more directly. Here is one recent study as an example:
"Biomed Pharmacother. 2017 Dec;96:305-312. doi: 10.1016/j.biopha.2017.10.001. Epub 2017 Oct 7.
Mechanisms of antidiabetic effects of flavonoid rutin.
Several lines of evidence suggest that flavonoids that originated from vegetables and medicinal plants have beneficial effects on diabetes by improving glycemic control, lipid profile, and antioxidant status. Rutin is a flavonoid found in many plants and shows a wide range of biological activities including anti-inflammatory, antioxidant, neuroprotective, nephroprotective, and hepatoprotective effects. In this review, the antihyperglycemic property of rutin and its protective effects against the development of diabetic complications are discussed. Proposed mechanisms for the antihyperglycemic effect of rutin include a decrease of carbohydrates absorption from the small intestine, inhibition of tissue gluconeogenesis, an increase of tissue glucose uptake, stimulation of insulin secretion from beta cells, and protecting Langerhans islet against degeneration. Rutin also decreases the formation of sorbitol, reactive oxygen species, advanced glycation end-product precursors, and inflammatory cytokines. These effects are considered to be responsible for the protective effect of rutin against hyperglycemia- and dyslipidemia-induced nephropathy, neuropathy, liver damage, and cardiovascular disorders. Taken together, the results of current experimental studies support the potential of rutin to prevent or treat pathologies associated with diabetes. Well-designed clinical studies are suggested to evaluate advantages and limits of rutin for managing diabetes."
The study concludes with the usual call for ‘further studies,’ but given that rutin, as a natural substance, cannot be patented to generate huge profits for the pharmaceutical industry, no one is going to come up with the money for those further studies, so, like most natural treatments for diabetes, rutin will always remain unproven.