@Lilliepop while searching for a book, I found at the bottom of one of my stacks, The Encyclopedia of Natural Medicine, 3rd Edition (2012). It's huge, 1,219 pages! I hadn't looked at it since last year so was curious as to what it had to say about diabetes.
Here's the second paragraph of what the naturopathic physicians wrote about alpha-lipoic acid (ALA)...
"Alpha-lipoic acid is an approved drug in Germany for the treatment of diabetic neuropathy and has been successfully used there for more than 30 years. The beneficial effects of alpha-lipoic acid in diabetic neuropathy have been confirmed in several double-blind studies at a dosage of 400 to 600 mg per day. (174,175) Although the primary effect of alpha-lipoic acid in improving diabetic neuropathy is thought to be the result of its antioxidant effects, it has also been shown to lead to an improvement in blood glucose metabolism, improve blood flow to peripheral nerves, and actually stimulate the regeneration of nerve fibers. Its importance in treating diabetic neuropathy cannot be overstated." (pp.539)
174. Reljanovic M, Reichel G, Rett K, et al. Treatment of diabetic polyneuropathy with the antioxidant thioctic acid (alpha-lipoic acid): a two year multi-center randomized double-blind placeb-controlled trial (ALA-DIN II). Alpha Lipoic Acid in Diabetic Neuropathy.
Free Radical Research 1999;31:171-179.
175. Jacob S, Ruus P, Hermann R, et al. Oral administration of RAC-alpha-lipoic acid modulates insulin sensitivity in patients with type-2 diabetes mellitus; a placebo-controlled pilot trial.
Free Radical Biology & Medicine 1999;27:309-314.
And here's the first paragraph...
"Alpha-lipoic Acid. Alpha-lipoic acid is a vitamin-like substance that is often described as "nature's perfect antioxidant". First of all, alpha-lipoic acid is a small molecule that is efficiently absorbed and easily crosses cell membranes. Unlike vitamin E, which is primarily fat soluble, and vitamin C, which is water soluable, alpha-lipoic acid can quench either water- or fat-soluable free radicals both inside the cell and outside in the intracellular spaces. Furthermore, alpha-lipoic acid extends the biochemical life of vitamin C and E, as well as other antioxidants such as glutathione, the most important intracellular antioxidant." (pp 539)
I hope you'll come back to let us know if it's helpful.