What is Glycemic Index?
Ranks how fast the carbohydrate in a food is digested and how sharply it cause an increase in the blood sugar level.
It is a number from 0-100 - With pure glucose given 100.
Classification of GI for a food: Low: < 55, Mid: 56-69, High: >70.
Carbohydrates with lower GI value ( 55 or less ) are more slowly digested, resulting in a lower and slower rise in blood glucose levels.
- Low GI: Green vegetables, most fruits, raw carrots, kidney beans, chickpeas, lentils and bran breakfast cereals
- Medium GI: Sweet corn, bananas, raw pineapple, raisins, oat breakfast cereals, and multigrain, oat bran or rye bread
- High GI: White rice, white bread and potatoes
What is Glycemic Load
A single food item usually contains a mixture of different classes of nutrients, eg. carbohydrate + fibre.
As GI ranks only the carbohydrate component value, GL gives a more accurate value based on how readily these carbohydrates are absorbed by the body based on the amount of that carbohydrate in relation to the rest of the other nutrients present.
Glycemic load of > 20 is high
Glycemic load of 11-19 is medium
And glycemic load of < 10 is considered low
Why follow a low GI / GL Diet?
- Help with diabetes management
Helps diabetics manage their glucose levels, cholesterol levels and reduce insulin resistance.
Studies have shown that low GI diets can help diabetics reduce their hba1c by 0.5% and reduce the risk of diabetic complications by 20%.
- Helps with weight management
Help achieve weight loss goals through appetite management, burn body fats and raise metabolic rates.
- Improve cardiovascular health
Can help improve heart health by improving cholesterol levels, especially LDL (Bad) Cholesterol.
- Help sustain energy levels
Low GI foods tend to be absorbed slower and utilised by the body over a longer period of time. This helps with concentration, energy and make you feel fuller for longer.
- Help with acne management
Research shows that a low GI diet can reduce acne!
Limitations of the glycemic index / load concept
GI of a food can vary due to
- Ripeness: the more ripe the fruits is, the more sugar it contains and hence a higher GI
- Cooking methods: Cellular structure is broken as food is cooked more thoroughly, making it easier to digest.
- Processing : Foods that are processed into finer particles tend to be more easily digested. Processing also destroys the fiber, resulting in higher GI.
- Ingredients: adding in other contents can change the GI of the food, eg acidic components like vinegar and lime reduces the GI of the food. FAT added into carbo can also reduce its GI.
Points to focus on for a healthier diet to achieve weight loss
1) Reduce overall food intake by 20-30%
2) Cut down on sugared and flavoured drinks and desserts.
3) Fresh food over processed
4) Take food high in fibre and protein
5) Eat food in entirety if possible - eg. Take potato with its skin to reduce the glycemic load.
By : Dr Chen Yiming
Family Physician, MBBS (Singapore), GDFM (NUS), GDFP Dermatology (NUS)