As long as you eat a reasonable amount of protein, the glucose you need for all bodily functions is supplied perfectly without any need to eat carbohydrate.
Fifty-eight percent of your dietary protein can be converted into glucose.
I have written a calculator that tells you how much protein you need to eat when you are on a ketogenic diet (one of approximately 100 g of carb a day or less.)
Calculate Your Protein Need on a Ketogenic Low Carb Diet
Note that the amount of protein you need to eat to supply glucose drops dramatically after 3 weeks because your brain adapts to burn ketones and needs far less glucose.
I have heard a lot of very stupid things from nutritionists about how without 130 g a day your brain stops running, etc. I published a bunch of books during the 6 years I ate about 60 grams of carb a day and my brain worked just fine the whole time!
I've been eating about 40 g a day thae past three weeks and taking hour long walks, mowing my acre of lawn etc. I take a bit of glucose with me on the walks, just to be sure, but so far, so good. When I eat this low a carb intake, I do not need any insulin except basal.
