Whoa, I'm a little stunned. After experimenting with various supplements for a few years to try and fix my starch tolerance, this is exactly the combo that seems to work. (I didn't see this thread when it first came out.)
My post meal BG's used to hit 150s 45-60 mins after a meal with 50g of starch, now it's <100. It's been like this for a few months now. It had been waxing and waning while I tried different supplement combos.
My supplement regimen includes half a 12 mg Iodoral 1x/wk, 3 tbsp raw potato starch daily (plus inulin and acacia powder on some days), 5,000 IU D3 with K2, and astaxanthin (an antioxidant which I have found no evidence online does anything for BG control). I stopped Metformin for a month and it seems to have no effect. (I plan to re-start for its anti cancer and longevity effects). I also stopped cinnamon and Chromium.
My diet is moderate-carb paleo (no grains, no industrial seed aka "veggie" oils, no processed sugar, and I get starch from tubers and white rice), and I eat 2 sometimes 3 square meals a day with no snacks, sometimes with good amounts of starch. I regularly eat homemade kefir.
I was never overweight and never had much insulin resistance, but I seemed to have poor first-phase insulin response to go with morning BG in the high 90s. When I first started taking potato starch the immediate effect was my 90 minute post meal BG dropped from 120s to 100, and morning BG to the low 90s.
While the Iodione, prebiotic, D3+K2 combo works great for me and for some others it may not work for everyone. It took me 2 years to find this combo. (would've been faster if I found this thread and tried it!). There are 11 subtypes as per Dr Scwartz, so every individual needs to figure out what works: