Hello. I'm not a medical professional, just the parent of a kid with type 1, and I am also not a nutritionist or dietician. From what I understand about type 2, it is primarily controlled by diet and exercise, sometimes requiring medicine. If you balance your diet with enough exercise to make up for it, theoretically you could eat those two foods with no problem. Corn meal is higher in carbs, so it would mean more activity, but it is clearly possible. Plantain looks like a really good fruit to have as part of your diet, it appears to have many nutritional benefits. I definitely think it's ok to have those foods. And as always, closely monitor your blood sugars with testing.
how does a diet of plantain help a diabetes patients diet
I will start by asking you a question. How is your blood sugar control? Are you able to keep your blood sugars consistently in the range of 70 - 120 (3.9 - 6.7)?
If you can keep your blood sugars in this range then your diet is fine. If your levels are much higher, then you will either need medications or to change your diet, or both.
Both plantains and cornmeal are very high in carbs. In diabetes, carbs are no longer able to processed properly, so eating a diet lower in carbs will help with control.
Lower carb foods will include meat, non-sweetened dairy (cheese, yoghurt, butter, cream), eggs, nuts, and non-starchy vegetables. Unfortuantely fruits and grains are very high in carbs, and may need to be limited by many.
Hope this helps you. Please ask more questions if you need.