Type 1 Diabetes Diet
All people with diabetes are advised to eat a healthy, balanced diet. This is a way of eating that is recommended for everyone.
However, people with Type 1 diabetes need to do more than just eat 'healthily'. The quantity, type and timing of your food choices are just as important as making sure that you have had your daily quota of fruit and vegetables.
Here, we focus on the effects of food on blood glucose levels and the relationships between insulin, diet and blood glucose levels in the management of Type 1 diabetes.
Carbohydrates, blood glucose and insulin
Carbohydrate foods have the greatest effect on blood glucose levels and it is the starchy foods - bread, cereals, potatoes, pasta, rice etc. - that you will need to pay most attention to you.
Carbohydrate foods are mostly broken down into glucose by digestive enzymes. The glucose is then absorbed from the intestine into the bloodstream (usually 1 - 2 hours after eating) and this causes the blood glucose level to rise. Insulin is needed so that the body's cells can take this glucose from the bloodstream and either use it for energy or store it for later. People who do not have diabetes will produce just the right amount of insulin to cope with the rise in blood glucose that occurs after a meal. Insulin on demand allows the person without diabetes to keep blood glucose levels within the normal range, even after a meal rich in carbohydrates.
Getting the balance right
If you have Type 1 diabetes then your body no longer produces insulin; you
have to inject it yourself. In order to keep the blood glucose level close to
normal after eating, you need to inject just the right amount of insulin to
deal with the food that you eat. It is also important that the injection is
timed right, so that the insulin is arriving in the bloodstream at the same
time that the glucose from the digested food is being absorbed from the gut.
If there is too little insulin (for the amount of glucose coming from the
digested food) then the blood glucose level will rise too high (hyperglycaemia).
If there is too much insulin (or not enough glucose coming from the digested
food) then the blood glucose level will fall too low (hypoglycaemia).
So, your food intake needs to be closely matched by your insulin
injections. This is why you will need to consider not only
what you
eat, but
how much you eat, and
when.
Different food types
The overall effect of a meal on the blood glucose level will depend on the
different types of foods making up the meal.
Glycaemic Index
Different types of carbohydrate foods are digested at different rates and
therefore have different effects in terms of raising the blood glucose level
after a meal. Some foods are quite rapidly digested to glucose (e.g.
cornflakes), whilst others take longer for the glucose to hit the bloodstream
(e.g. All-Bran
TM). The effect of different carbohydrate foods on
blood glucose levels has been quantified by the Glycaemic Index (GI). Foods
with a low GI cause less of a spike in post-meal blood glucose than those with
a high GI.
Sugar
It is still widely believed amongst the general population that people with
diabetes should avoid eating sugar because it causes a rapid increase in blood
glucose levels. This is not true! Table sugar, which we sprinkle on our
cornflakes, actually causes less of a spike in blood glucose than the
cornflakes themselves. Sucrose*, surprisingly, has a lower GI than cornflakes.
As part of healthy eating, we are all advised to cut down on sugar - this
is because it has little nutritional value, it does little to satisfy the
appetite and it's a source of 'empty calories'.
*Important note:
Table sugar is not the same as glucose. Table sugar is called sucrose and
is a disaccharide - it contains two sugar molecules: one fructose and one
glucose. Table sugar needs to be broken down by digestive enzymes before the
fructose and glucose can be absorbed. Glucose is absorbed quickly because it
does not need to be broken down (digested) first.
Protein and Fat
Carbohydrate foods have the greatest effects on blood glucose levels
because they are mostly digested to glucose, which is absorbed from the
intestine straight into the bloodstream. However, proteins and fats in the
diet affect blood glucose levels too.
Excess protein in the diet that is not needed by the body is converted to
glucose by the liver. This means that consuming large amounts of protein can
result in an increase in blood glucose levels several hours after eating.
The most significant effect of fat is probably to slow down the rise in
blood glucose after a meal. Fat delays the rate at which the stomach empties -
this has the knock-on effect of slowing down the absorption of glucose from
digested carbohydrate foods. You might think that this is a good thing, but
remember that a high-fat diet is not necessarily a healthy diet.
Putting the theory into practise
Remember, your aim is to keep blood glucose levels close to normal. Eating
causes the blood glucose level to rise; the aim of your insulin injections is
to minimise 'post-meal spikes' in blood glucose without causing
hypoglycaemia (low blood glucose).
In order to understand the relationship between the food that you eat, your
blood glucose levels and the insulin that you inject you will need to learn
about the different types of insulin that make up your insulin regimen. You
should know when the insulins act and which parts of your insulin regimen aim
to cover which meals.
Should my meals be tailored to my prescribed insulin regimen?
In years gone by, people with Type 1 diabetes were advised to stick to
quite a rigid meal schedule, which was determined by their insulin injections.
Some insulin regimens still call for this to a certain extent. However, these
days it is generally recognised that it is better to derive an insulin regimen
that suits the individual person's lifestyle.
So, in most cases insulin should be tailored to your food intake and not
the other way round. This assumes that you are eating a healthy and nutritious
diet that fulfils your needs.
To start with then, you will need to find the right insulin doses for an
'average' day in your life. In practical terms, you will need to eat a normal
healthy diet, trying to eat roughly the same at the same time each day. Using
blood glucose monitoring to guide you, the timing and/or dose of your insulin
injections can be adjusted. Your healthcare team will help direct you in this.
Your aim is to establish a routine, which gives reasonable control of your
blood glucose levels, and fits in with your lifestyle. Then you can work from
this baseline, fine-tuning your control and perhaps also introducing more
flexibility.
Snacks
An important role of diet in managing Type 1 diabetes is preventing low
blood glucose levels (
hypoglycaemia).
Some insulin regimens require you to have snacks in between meals in order
to prevent hypoglycaemia. Snacks are not always necessary though, so check
with your doctor and/or dietitian to see if you need to snack between meals.
A bedtime snack is, however, essential for all people with Type 1 diabetes.
This ensures that blood glucose levels don't fall too low during the night.
Snacks are also very important before exercising, especially if the
activity does not form part of your regular daily routine. This is to prevent
exercise-induced hypoglycaemia.
Accommodating change
In practise, most people have a regular insulin regimen, which is tailored
to their 'average' day. The insulin dose and timing of the injections relates
to how much is usually eaten and when. In theory, you will know that your
insulin dose is just right for your 'normal' eating pattern. Any changes you
might make to your usual day may need to be catered for by an appropriate
tweaking of the insulin dose. Your diabetes team will be able to give you
personal advice on how to make adjustments to cope with changes to your normal
schedule.
As a general rule, more food (especially carbohydrates) needs more insulin,
otherwise the blood glucose level will rise too high. Less food (especially
carbohydrates) needs less insulin, otherwise the blood glucose level will fall
too low. It is important to get the adjustment just right - or you may find
that you have overcompensated for the change and given too much or too little
insulin.
Use blood glucose monitoring to find out whether your adjustments are
working; make a note in your diary of the changes you made and learn from
experience. The most informative times to test are before eating and then 1 -
2 hours after your meal.
Delayed or missed meals are probably the most common cause of hypoglycaemia.
Take steps to avoid low blood glucose levels if you know that you are not
going to be able to eat your usual meal. Have an extra snack to keep you going
and keep an eye on your blood glucose level.
Fine tuning your diet
Use your blood glucose test results and your knowledge of the effects of
food on YOUR blood glucose levels to fine tune your diet for better control.
Here is a summary of some of the main points for your consideration:
(From www.diabetes-insight.info)