Most common advice to diabetic patients is to eat roti or chapathi or any wheat products. It is assumed that this will help in the reduction of sugars. Sadly i have hardly seen much help in the matter. Many switch from rice to wheat products and assume they have done the right choice.
Nobody ever think about the servings and end up eating the same amount of servings/number of chapathis Eg.5- 8 Nos. What is very important in diabetes is the kind of carbohydrate eaten or the kind of sugar. Hence eating many chapathis do not reduce in fact can increase sugar levels.
Doctors too ask patients to switch to chapathi. But especially for south indian, rice is the main cereal other than ragi,jowar etc.
Yes rice can be safely eaten so also wheat ie by eating the same servings Eg 3 katoris of rice or 3 chapathis or 1 katori rice plus 2 chapathis in a normal diet. In a low calorie, reducing diet only 2 servings of any cereal is allowed.
One serving of rice is 25 grams of raw, uncooked rice and that of wheat is 25 grams of whole wheat flour from which a single chapathi will be obtained.
Any cereal locally eaten should be eaten in the quantities obtained above.
What so far I have explained from a technical point of view. If I see from a practical point of view, Chapathi can help in portion control. Nobody weighs the quantity of rice( I strongly advise you should atleast know the quantity) but the number of chapathis can be counted to eat the right amount of carbohydrates in each meal.
So do not blindly eat chapathis for sugar control, check how many are you eating.