The first thing to realize is that nutritional supplements can very successfully control blood sugar in diabetics. Both green tea and cinnamon are well-known to help control blood sugar so that you don't have such wild blood sugar swings (and potentially don't need as much insulin either). Also, there are many other benefits documented from taking both green tea and cinnamon. Green tea is noted for its anti-cancer effects, as well as its ability to aid in weight-loss, which is something that diabetics are typically concerned with. However, one concern of mine is that green tea usually contains caffeine, and caffeine, as we know, is contraindicated for diabetics. Accordingly, my advice is that green tea supplementation be limited if you are diabetic so that you don't end up overdosing on caffeine and throwing your blood sugar out of whack.
Aside from the fact that these nutritional and herbal supplements can help stabilize blood sugar, there's a bigger question of whether diabetics should be using these sorts of nutritional supplements to help control their blood sugar in the first place. As much as I believe in nutritional supplements and the power of medicinal herbs to help people with diseases like diabetes and cancer, I think there is also a danger of using them as a crutch and ultimately relying on these healing herbs rather than making lifestyle changes that will reverse the diabetic condition in the first place.
Or, stated another way, most people who are diabetic attained that state of health by following a lifestyle that promotes diabetes. This sort of lifestyle includes consuming soft drinks and lots of foods with sugars and refined carbohydrates. It's typically a lifestyle of exercise avoidance and avoidance of strength training. People who are diabetic also tend to be overweight. They tend to eat at fast-food restaurants and consume foods that promote obesity. Most of these people also continue to pursue this lifestyle even while they are diabetic. In other words, once they are diagnosed with diabetes, they very rarely change these habits: they continue to consume soft drinks, refined white sugar, products made with white flour, such as bread, and they continue to avoid physical exercise.
In this scenario, consuming one or two doses of green tea extract and cinnamon is not really going to do you much good. The product may be perfectly effective as claimed, but there's no way that one nutritional supplement can counteract an extremely toxic lifestyle that promotes diabetes, weight gain, and other chronic diseases. So, for diabetic patients who are considering nutritional supplements like this one, I would say that, yes, it's good to pursue supplements that help stabilize your blood sugar, but it's far more important to alter your lifestyle and stop following the habits that made you diabetic in the first place. If you do both, together -- that is, if you alter your lifestyle and start choosing healthful foods while engaging in regular physical exercise -- and start taking these nutritional supplements at the same time, you will be far healthier than doing either one alone. It is only in combination that these complementary therapies really make sense.
The bottom line is that you should never rely on these products to take over your responsibility for leading a healthy lifestyle in the first place. However, if you make changes and begin to pursue a healthy lifestyle, then adding these products to your list of strategies for preventing and even reversing diabetes is perfectly justified.