The Truth About Carbs
1. Not all carbohydrates are the same!
People with diabetes are advised to choose starchy carbohydrate foods - such
as bread or potatoes - in preference to sugary foods, as starchy food would
raise their blood glucose more slowly. So it can come as a surprise to find
that, when you test your levels, some starchy foods raise your blood glucose
almost as quickly as sugar.
A good example would be white bread. If you eat white bread it can raise
your blood glucose just as quickly as eating simple sugar and more quickly
than, for example, chocolate!
So is this advice wrong? Well not completely, but the situation is more
complicated than was first thought. Read on to find out how by choosing your
carbohydrate foods carefully you could improve your blood glucose levels.
2. How carbohydrates differ
The carbohydrate in the food you eat is digested by breaking it down into
glucose, which your body uses for fuel. The speed at which you carry out this
digestion depends upon three factors:
- The type of carbohydrate:
It appears that the speed a starchy carbohydrate food is digested depends upon
its structure. Carbohydrates are made up primarily of glucose molecules linked
together into two main types of structure: amylopectins, where the links have
lots of branches; and amylose, where the molecules are linked in long straight
chains. The more long straight amylose chains there are in a carbohydrate, the
more resistant it will be to digestion, so the longer it will be before the
glucose molecules reach your blood.
- The other constituents in the food:
Other constituents in a food can alter the rate it is digested and absorbed.
Chocolate, for example, while full of sugar, also contains considerable amounts
of other carbohydrates as well as protein and fat. The consequence is that the
effect of chocolate on your blood glucose is not as dramatic as you might
expect.
- The other foods that are eaten at the same time:
In the real world we seldom eat single foods in isolation; generally they are
part of a meal containing not only carbohydrate but also a mixture of fats,
protein and fiber. All these constituents can slow the absorption of the
carbohydrate.
3. Ranking carbohydrate foods
To untangle this complexity, carbohydrate foods have now been ranked
according to how rapidly they affect your blood sugar levels. An index has been
invented, called the Glycemic Index (GI), which places them on a scale of 0 to
100.
Glucose or white bread is given the index 100; other foods are ranked
against this.
- Foods with a high GI are quickly digested and absorbed and can rapidly
raise your blood glucose.
- Foods with a low GI are slowly digested and absorbed and so raise your
blood glucose more gradually.
As the following table shows the effect of some foods can be surprising:
High
(Raise your blood glucose quickly)
|
Medium |
Low
(Raise your blood glucose slowly) |
| Food |
Index |
Food |
Index |
Food |
Index |
Glucose
|
100 |
|
Sweet corn |
54 |
| Baked potato |
85 |
Couscous |
65 |
Custard |
43 |
| Brown rice |
79 |
White rice
(basmati) |
58 |
Chocolate |
43 |
| Mashed potato |
74 |
Honey |
55 |
Pasta (spaghetti) |
42 |
| White bread |
70 |
Jam
(strawberry) |
51 |
Apples |
38 |
| |
|
|
Beans and lentils |
29 |
4. Benefits of slow acting carbohydrate
- Meals with a low GI can give you a smoother level of blood glucose through
the day, avoiding hypoglycemia and also preventing blood glucose from rising
too high.
- Low GI foods can help with weight loss as they make you feel fuller for
longer so you eat less.
- Some research has shown that low GI diets may lower your risk of heart
disease.
5. Eating a low GI diet
Choosing a low GI diet is a bit more complicated than just looking up the
index in a book - although there are plenty of books available. Don't forget
that the GI level is for a food eaten alone and we tend to eat foods in groups,
as a meal. Even the method of cooking you use can affect the GI.
To get started, here are a few simple tips:
- Try including low GI foods in every meal; they can slow the absorption of
the other food.
- Choose the main carbohydrate in your meal carefully and add lots of
vegetables. Remember pasta, for example, has a lower GI than bread or
potatoes.
- Avoid chocolate and nuts as snacks if you are trying to lose weight; they
may have a relatively low GI but they contain lots of calories!
Try a few experiments with your favorite meals. Test to see how much they
raise your blood glucose, then try substituting some of the ingredients with
lower GI equivalents next time around and see if your glucose levels improve
after you have eaten.
Watch out for hypoglycemia as your treatment requirements may change.
6. Finding out more
Low GI diets are becoming increasingly popular and there is an ever-growing
number of books on the subject. In these books the low GI diet is mainly
being described as a weight reduction program but many contain useful
information, plus tables of the main low GI foods to help you put together your
diet plan.
There are several places on the internet where you can purchase such books
(Amazon is one example).
Important Notice: Information provided is for general
background purposes and is not intended as a substitute for medical diagnosis
or treatment by a trained professional. You should always consult your
physician about any health care questions you may have, especially before
trying a new medication, diet, fitness program, or approach to health care
issues.