The Glycemic Index, or in the world of complicated UK spelling - Glycaemic Index,
is a measurement of how much sugar (glucose) is absorbed into the blood in a fixed time period,
after eating a portion of the food with a fixed quantity of carbohydrate.
The glycemic index is often abbreviated to just GI.
Choosing foods with a lower GI rating should cause a slower rise in blood sugar levels after a meal.
Mixing foods that are low on the GI scale with foods that are high on the GI scale,
produce a medium GI rated meal.
This could be anything from have more green vegetables with your potatoes,
to replacing some or all of the potatoes or white bread with beans,
durum wheat pasta or granary bread its your choice!
In practise when mixing foods in a meal its certainly not an exact science.
However it can be very useful in helping to choose foods that don't raise blood sugar levels too high.
The sugar absorption rate shown on the other diet pages is based on figures from the detailed tables at the end of the page.
To simplify the tables on the other pages of this site, they show the foods blood sugar conversion speed in 4 bands.
These are: - Quick, Medium, Slow and Very Slow
|Foods with a quick conversion to blood sugar:||GI 60 or more|
|Foods with a medium conversion to blood sugar:||GI 59 to 40|
|Foods with a slow conversion to blood sugar:||GI 39 to 20|
|Foods with a very slow conversion to blood sugar:||GI 19 or less|
Note that that other sites and many commercial products use the terms of 'high gi', 'medium gi' and 'low gi'.
I find these definitions of limited use as a diabetic.
Mainly because the 'low gi' definition is so broad.
For more information see the
band information comparison page.
A low GI diet does not necessarily result in weight loss!
If you follow a 'low GI diet' and
reduce calories you can lose weight!
To lose weight you still need to consider the overall number of calories you eat and drink.
It may be helpful in losing weight though.
The theory is: Foods that release energy slowly,
that is convert to blood sugar slowly are more satisfying over a longer period.
Where as foods with a quick conversion to blood sugar give a short but very high release of energy and leave you wanting more quickly.
If you have low blood sugar (hypoglycemia or just hypo) you can have a snack of foods with a
quick conversion to blood sugar to give a quick boost to blood sugar.
Take care not to over do it though with not to large a snack.
If its a while to your next meal too,
you may wish to 'top up' with some medium rated GI foods to keep you going until your next meal time too.
Athletes use the GI tables too.
Using the tables to choose foods that give a slower but sustained release of energy for long term endurance sports,
like the Bristol Marathon pictured.
This sustained release helps them maintains their blood sugar levels during prolonged exercise.
In a meal, balance a portion of quick rated foods with a portion of slow rated foods to get a medium rated meal.
Compared with meals made from foods with a quick conversion to blood sugar.
Meals made up from foods that are medium to slow rated give a slower but more sustained conversion to blood sugar.
This often causes lower peak blood sugar levels.
Don't expect that just adding a few slow GI rated onions to a burger in a bun with chips will help greatly.
Will have a very little effect when eaten on there own.
Better yet, when eaten in a meal with other quicker rated foods (that is food with a higher GI),
they lower the meals overall GI level.
Typically these are foods like green vegetables and many salad vegetables,
with to little carbohydrate to test easily they are not included in the tables.
Tomato with more carbohydrate than many salad vegetables is quicker to convert to blood sugar but still slow rated.
Fish and Meat (without added potato, bread crumbs, cereals and any other carbohydrate sources)
are also very low carbohydrate.
Fish and Meat however lack fibre,
so when eaten as part of a meal.
While they will have some effect in slowing the meals conversion to blood sugar and lower the overall meals GI.
They may have less effect than high fibre salad and green vegetables.
Length of cooking time will also effect the GI.
Food breaks down into more easily digestible forms during cooking and generally the longer food is cooked
the quicker the food is digested and converted into blood sugar.
If you browse the internet you may come across two different GI figures for the same item.
The tables below and all figures on this site are based on Glucose having a value of 100,
White Bread is 70 to 71 on this scale.
The other scale is based on White Bread having a GI of 100,
Glucose has a GI of about 143 on this scale - very confusing!
To check which one is being used just lookup the GI for white bread - if its 70'ish its using this scale.
Aim for a varied and balanced diet.
Take care with the amount of calories and fat,
especially saturated fat and hydrogenated fat.
Low carbohydrate (low carb) diets are not recommended either.
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|BEANS & PEAS (LEGUMES)|
|Baked Beans Tinned||43-49|
|Black (Eyed) Beans||30|
|Broad Beans (Fava)||81|
|Navy Beans (Haricot)||38|
|Dark Rye bread||76|
|Heavy Mixed Grain||30-45|
|Milk, Full Fat||27|
|Yoghurt low fat, unsweetened||14|
|Yoghurt, low fat, sweetened||33||
|Fish Cakes, Fish Fingers, Breaded & Battered Fish.||?|
|FRUIT & VEGETABLE JUICE|
|Apple Juice (Cloudy)||37-42|
|Apple Juice (Clear)||44|
|Pineapple Juice (suspect)||46?|
|Black (Blood) Pudding, Burgers, Sausages, Pies ...||?|
|PASTA (DURUM WHEAT)|
|Rich Tea Biscuits||57|
|Potato: Jacket Baked||60?-85|
|Potato: Boiled or Mashed||74|