Treatment Diabetes: insulin and diet (part 1)

We asked a few questions of patients who have diabetes: is it possible to sit on a diet during diabetes, and occurs as treatment with insulin. On this read in this and subsequent articles.

DIET AND INSULIN

I understand that different forms of carbohydrate have different rates of digestion and that this affects the rise in blood glucose after a meal. I gather there is a ‘glycaemic index’ for each type of carbohydrate. What is this glycaemic index?

The glycaemic index (Cl) is a measure of how quickly foods that contain carbohydrate raise blood glucose levels. Each food is given a number relating to its effect on blood glucose. Foods with a high Gl are quickly converted to glucose when eaten and cause a sharp rise in blood glucose levels. Foods with a low Gl are converted to glucose much more slowly and produce a more gradual rise in blood glucose. The Gl only tells us how quickly a food raises blood glucose when it is eaten on its own and as we usually eat a combination of foods this can change the overall Gl of a meal. We do not recommend cutting out all foods with a high Gl because your diet needs to be appealing as well as balanced. Low Gl foods are generally more filling and can help control hunger as well as blood glucose levels, so they may help with weight loss. You need to be aware that the portion of carbohydrate is also important so eating large quantities of low Gl foods can still affect your overall control. Some low Gl foods, such as crisps and chocolate, are higher in fat and calories, so choices have to be made sensibly.

Knowing which foods have a high Gl can be helpful for treating hypos as these will raise blood glucose more quickly.

How long before eating should I have my insulin injection?

The answer depends on the speed of onset of the insulin you are using.

If you are taking one of the fast-acting analogue insulins such as Humalog or NovoRapid, this should normally be injected just before a meal. However, some people prefer to inject immediately after the meal, when they know exactly how much they have eaten.

The older short-acting insulins, such as Actrapid and Humulin S, take longer to have their effect and ideally should be taken 30 minutes before your meal. If your pre-meal blood glucose is low you should delay your injection until you are ready to eat.

I am on two injections a day. Sometimes I find it inconvenient to take my evening injection. Can I skip it and have a meal containing no carbohydrate?

It would not be a good idea to skip your second (evening) injection, as this would leave you without insulin cover overnight. As the effect of your morning injection wears off, your blood glucose levels will rise even if you have eaten no carbohydrate. Insulin pens are easy to carry and should make it relatively easy to inject in most situations. If you need more flexibility in your insulin regimen then speak to your diabetes specialist nurse, who could explain alternative regimens for you to consider.

To be continued…