This vegan, low oil, "low glycemic index" diet will undoubtedly, if adopted, constitute a great improvement for many diabetic patients, both types 1 and 2. These individuals will lower their blood sugars, reduce their medication and lose weight, as indeed was the case with the patients referred to in the book.
However, I do not subscribe to Dr. Barnard's allowance of sugar, nor his recommendation to eat generous amounts of fruit, no matter how much he claims these fruits have a low GI. Sugar is sugar, and fruit sugar is just as harmful to a diabetic as sugar cubes. My own type 1 diabetes was provoked by my eating too many bananas (although admittedly I had a preliminary history of undiagnosed hypoglycemia.) Bananas are permitted in this diet, but having become ill by consuming these, I have no faith in being able to cure myself by continuing to eat them (1 banana = 7 teaspoons of sugar). He even finds dried fruits acceptable.
Moreover he has no objection to processed foods/instant soups found in packets or tins, that are generally filled with deleterious additives, sugar, white flour, etc. etc. (he recommends baked beans, but even the organic tinned baked beans I found in my local supermarket contain 13.8% sugar.) Nor has he any objection to the use of non-stick pans or microwave ovens, that are known to be dangerous. In fact he recommends their use.
He bans fish (owing to its high fat content), though it is generally accepted that fish are to be recommended, as they contain beneficial oils. On the whole, he does not distinguish between healthy and unhealthy oils, and does not seem to realize that we need omega 3-containing oils such as flaxseed oil.
He states that by foilowing his diet we will exclude all cholesterol, this being found only in animal foods. But according to Joel Wallach in his book "Dead doctors don't lie" a certain amount of cholesterol is necessary, since one can die from too little as well as too much cholesterol. I wouldn't know, not being an expert. I certainly believe that the consumption of eggs does not raise one's cholesterol level unless they are fried in unhealthy fats/oils.
Under any circumstances, I'm not sure that the author's extreme low-fat diet is in any way necessary for type 1 diabetics, since he explains that his diet was put together on the basis of research indicating that type 2 diabetics have an excess of fat inside their muscle cells that interferes with insulin's intracellular signalling process, resulting in insulin resistance. Therefore they are helped by a low-fat diet. But type 1 diabetics do not suffer from insulin resistance but from a faulty pancreas that has difficulty in producing insulin, so why should they exclude beneficial oils?
Dr. Barnard's tenet that the addition to the diet of a standard multi-vitamin including B12 will provede "complete nutrition" is ludicrous. Though he does in a later ultra-short chapter provide an absolutely minimal list of recommended supplements.
To sum up, this book will absolutely be helpful for those type 2 diabetics who are prepared to commit to following the diet, but since he admits it will not cure type 1 diabetics I would rather follow Cass Ingram's diet as described in his book "Natural cures for diabetes". And I feel that avoiding healthy oils to the extent prescribed by Dr. Barnard could be harmful in the long run.