Certain types of diabetes can be controlled just with diet, which I am guessing comes under "natural" methods. Many cannot though. For many, such as those with type 1 diabetes like myself, you can choose between the 2 following options: take insulin/pills every day or die slowly. Perhaps cutting carbohydrate from your diet might slow the damage (though I am not sure of this), but the outcome will be inevitable and with the understanding and manageability of the disease offered by modern medicine, it would be utter foolishness to go for some silly 'alternative' like homeopathy or something.
Currently it is not curable and can only be 'managed' so as to minimise damage to the body, though stem cell research options are being tested and it is believed a cure is only a few years away.