"a substitute for oral insulin" is an interesting concept as there is no such thing as oral insulin available to us diabetics. The digestive system destroys insulin. That's why we inject. There is one that can be inhaled, but is not in wide use, and some problems have been reported (damage to the lungs).

I think they mean it just lowers blood sugar. Some other natural remedies tend to have a similar effect, (e.g. cinnamon). They may help a mild type 2 diabetic lower their blood sugar, but they do not substitute for insulin. Type 2 diabetics have trouble using the insulin their bodies produce, and some compounds seem to help the body use the natural insulin better.

On the other hand, if you don't have your body's insulin to use in the first place, such natural compounds will not help. For example, in my case I inject insulin 3x a day. My pancreas pretty much gave up on producing insulin about 10 years ago.

However, I will last longer than 2 weeks. I have a 3 month supply in the fridge at any one time.