What is the Glycemic Index (GI)?
In really simple terms, the glycemic index (GI) is a ranking of carbohydrates on a scale from 0 to 100 according to the extent to which they raise blood sugar levels after eating. Foods with a high GI are those which are rapidly digested and absorbed and result in marked fluctuations in blood sugar levels – think white sugar and some white breads such as a baguette.
On the other hand low-GI foods, by virtue of their slow digestion and absorption, produce gradual rises in blood sugar and insulin levels, and have proven benefits for health. They have also been shown to be very effective in weight-loss over a period of time because they help control appetite and delay hunger. Low GI diets improve both glucose and lipid levels in people with diabetes (type 1 and type 2) and also reduce insulin levels and insulin resistance.
So why worry about the GI?
Recent studies from Harvard School of Public Health indicate that the risks of diseases such as type 2 diabetes and coronary heart disease are strongly related to the GI of the overall diet. In 1999, the World Health Organisation (WHO) and Food and Agriculture Organisation (FAO) recommended that people in industrialised countries base their diets on low-GI foods in order to prevent the most common diseases of affluence, such as coronary heart disease, diabetes and obesity.
What is the difference between glycemic index (GI) and glycemic load (GL)?
Your blood glucose rises and falls when you eat a meal containing carbs. How high it rises and how long it remains high depends on the quality of the carbs (the GI) and the quantity. Glycemic load or GL combines both the quality and quantity of carbohydrate in one ‘number’. It’s the best way to predict blood glucose values of different types and amounts of food.
What fruit and veg are low GI?
- Temperate climate fruits – apples, pears, citrus (oranges, grapefruit) and stone fruits (peaches, plums, apricots) – all have low GI values.
- Tropical fruits – pineapple, paw paw, papaya, rockmelon and watermelon tend to have higher GI values, but their glycemic load (GL) is low because they are low in carbohydrate.
- Leafy green and salad vegetables have so little carbohydrate that their GI cannot be tested. Even in generous serving sizes they will have no effect on your blood glucose levels.
- Higher carb starchy vegetables include sweet corn (which is actually a cereal grain), potato, sweet potato, taro and yam, so watch the portion sizes with these. Most potatoes tested to date have a high GI, so if you are a big potato eater, try to replace some with lower GI starchy alternatives such as sweet corn, yam or legumes or look for a low-GI potato variety.
- Pumpkin, carrots, peas, parsnips and beetroot contain some carbohydrate, but a normal serving size contains so little that it won’t raise your blood glucose levels significantly.
Where can I get more information?
Check out: www.glycemicindex.com