Hej
Hej Scandichic. Well every person is different so you have to test systematically to see how a food affects you. For me, rye breads and rye crispbreads, in moderation were OK from the outset. A rye bread like pumpernickel or a crispbread like dark rye ryvita are foods with a medium glycaemic index. The GI of a food is a reflection of how quickly it spikes your blood sugar levels compared against glucose. Glucose has a GI of 100. It has a higher glycemic response curve than other foods, the graph below being typical for someone with a normal insulin response:
One of those large Peter's Yard crispbreads is about 70g and has about 42g carbs. Some of those carbs though are fibre, which are not fully digested. Wholegrain Ryvita for example has about 68g carbs per 100g but 15g of that is cellulose based, ie, you don't digest it. It's as if it is only 53g carbs. However, those carbs are more complex carbs which take longer to break down, hence it has a lower GI. 4 ryvita crispbreads are about 24g total carbs or 18 g complex carbs, so it really is how you define low cabohydrate.
The brain needs 130g which is about 60% of the total requitrement of the body. If it doesn't get its glucose directly from the blood supply, the body generates its own from various fatty acid stores. I've always based my calculations on a requirement of 200g carbs of which I eat 100g, giving me enough for immediate purposes and leaving the body to create the other 100g from its own stores via a process called
gluconeogenesis
It can always be a bit tricky to begin with because your metabolism has to get used to things and the way you mix and match the foods you eat also makes a big difference to how it is digested. You have to try and get some sort of system which allows you to test. Also, portion control is important. Start with two crackers and test. Even if two crackers don't spike you, don't rush for 4, Stay with two for a few days. Gently does it, be watchful and beware of trolls.