The epidemic of diabetes is recent. So why would ancient remedies be effective?
Also - Cholesterol is not actually a disease, damage cholesterol is. Elevated cholesterol does not infer cardiovascular risk unless it's damaged
In one study, bitter melon extract significantly lowered fasting blood glucose in people with type 2 diabetes after four weeks.
https://doi.org/10.1016/j.jep.2010.12.045
Bitter melon had a modest hypoglycemic effect and significantly reduced fructosamine levels from baseline among patients with type 2 diabetes who received 2000 mg/day. However, the hypoglycemic effect of bitter melon was less than metformin 1000 mg/day.
It's curious, to be sure, but if someone is fighting t2d they are better advised to remove glucose from their food Rather than eating a lot of glucose and using bitter melon to try to reduce it in the blood.