What is the Glycemic index (GI) and GI food list

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What is the Glycemic index (GI) and GI food list

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What is the Glycemic index (GI)? 

Glycemic index (GI) is a method used to determine the potential of foods to raise blood sugar levels. 

The GI value is calculated by measuring the blood sugar response of a given food (test food) and comparing it to the response of the reference food or pure glucose. 

The reference food is mostly white bread and the standard weight of the test and reference food is 50 grams (1). 

The glycemic index was developed by Dr. Jenkins in the 1980s to better understand the potential of dietary carbohydrates on diabetes (2).

In essence, the GI value represents the quality of the carbohydrates in the food. A good quality carbohydrate has a low GI value and a bad quality carbohydrate food has a high GI value (3).

Why Glycemic index is used?

Diet is a crucial component for managing diabetes. Thus, a good diet plan requires food choices that help control the level of blood glucose (sugar) levels. 

Traditionally, the blood sugar (glucose) response was determined by how much carbohydrates are present in a given food. This led to the development of diets that provided information based on carbohydrate content. 

But in reality, foods with a similar carbohydrate content do not have the same impact to raise the blood sugar level. 

The glycemic index does exactly this. It classifies carbohydrate-containing foods based on their potential to raise blood glucose levels. 

Glycemic index categories

There are three categories of foods based on the Glycemic Index (4).

  1. High GI foods (more than 70)
  2. Intermediate GI foods (between 55 and 70)
  3. Low-GI foods (less than 55)

Foods with high GI values cause a rapid increase in blood glucose levels thus, prompt a quick insulin response. Whereas, foods low in GI value induce a low insulin response. 

The factors that determine GI values are types of carbohydrates, fats, proteins, fiber, and pH. 

As mentioned earlier, GI is a good indicator of the potential of carbohydrate-based food to raise blood glucose levels. It is a good tool to understand the quality of carbohydrates, however, the quantity aspect is not considered.

GI does not tell us how long or how increased sugar levels in the blood will be after eating a certain amount of carbohydrates.

The idea of GI has been extended to include the quantity of carbohydrates.

It is called the Glycemic Load (GL). 

GL combines GI and the amount of carbohydrate taken.

GL = GI × available carbohydrate (g) /100

To have a clear understanding of carbohydrates and blood glucose-raising potential we need both quality and quantity of carbohydrates (5).

For example, carrots have a GI value of 131 which is considered high, however, 100 grams of carrots have very little carbohydrate thus, it has a value of less than 4 GL which is considered low GL. 

GL has 3 categories.

These categories of GL are given below (6)

  • Low GL (less than10)
  • Intermediate (between 11–19) 
  • High (more 20)

It is important to consider Glycemic load when making food choices in addition to the Glycemic index.

Benefits of Glycemic index

GI and diabetes 

he Glycemic index was developed to help diabetics better manage their glucose and weight. 

Research shows no clear evidence of a positive association between GI and indicators of diabetes. 

Healthy individuals who followed a low GI diet had lower fasting glucose and insulin-like growth factor 1 (IGF-1) compared to a high GI diet (7).

Increased risk of type 2 diabetes is observed in individuals with increased GI food consumption in both men and women (8,9).

Obese or overweight individuals were at the most risk among the participants.

However, other long-term studies did not show a significant risk association between type 2 diabetes and low GI (10,11,12).

But these studies indicate more fiber and vegetable consumption with a low risk of diabetes.

These particular studies and other research indicate that GI may have a glucose-lowering impact but entirely relying on GI foods will not be sufficient to control diabetes. 

GI and weight loss

Research shows that taking low GI and energy-restricted diet food affects body weight (13, 14).

However, other studies have found no significant effect of low GI food consumption and weight loss (15, 16). 

Like the studies for diabetes, a GI diet alone may not be enough to manage weight. 

GI and brain health

Glucose is fuel for the brain. Is there an association between GI and brain health?

Research shows that low GI and GL food consumption is associated with better cognition and brain function in elderly people. On the contrary, high GI consumption is associated with low brain function (17, 18, 19).

Also, a decreased risk of dementia and Alzheimer’s disease is also associated with low GI. However, these observations are heterogeneous. Therefore, a clear conclusion cannot be drawn (20).

In summary, these mixed results of GI diet and its health benefits are due to differences in study design and other factors such as fiber content or cooking method. Therefore, GI or GL alone cannot be used when making food choices. 

Glycemic index of most common foods. 

Here is the list of the most common carbohydrates source and their GI (21).

Cereal bowl with milk
Cereals (Breakfast)Vegetables
Food NameGlycemic indexFood NameGlycemic index
Cornflakes81 ±6Potato, boiled78 ±4
Wheat flake biscuits61 ±2Potato, instant mash87 ±3
Porridge rolled oats55 ±2Potato, french fries63 ±5
Instant oat porridge79 ±3Carrots, boiled39 ±4
Rice porridge/congee78 ±9Sweet potato, boiled63 ±6
Millet porridge67 ±5Pumpkin, boiled64 ±7
Muesli57 ±2Plantain/green banana55 ±6
Taro, boiled53 ±2
Vegetable soup48 ±5
Cake with cream and fruits
Fruit and fruit productsHigh-carbohydrate foods
Food NameGlycemic indexFood NameGlycemic index
Apple, raw36 ±2White wheat bread75 ±2
Orange, raw43 ±3Whole wheat/wholemeal bread74 ±2
Banana, raw51 ±3Specialty grain bread53 ±2
Pineapple, raw59 ±8Unleavened wheat bread70 ±5
Mango, raw51 ±5Wheat roti62 ±3
Watermelon, raw76 ±4Chapatti52 ±4
Dates, raw42 ±4Corn tortilla46 ±4
Peaches, canned43 ±5White rice, boiled73 ±4
Strawberry jam/jelly49 ±3Brown rice, boiled68 ±4
Apple juice41 ±2Barley28 ±2
Orange juice50 ±2Sweet corn52 ±5
Spaghetti, white49 ±2
Spaghetti, wholemeal48 ±5
Rice noodles53 ±7
Udon noodles55 ±7
Couscous65 ±4
Fruits in a wood box
Dairy products and alternativesLegumes
Food NameGlycemic indexFood NameGlycemic index
Milk, full fat39 ±3Chickpeas28 ±9
Milk, skim37 ±4Kidney beans24 ±4
Ice Cream51 ±3Lentils32 ±5
Yogurt, fruit41 ±2Soya beans16 ±1
Soy milk34 ±4
Rice milk86 ±7
Snack productsSugars
Food NameGlycemic indexFood NameGlycemic index
Chocolate40 ±3Fructose15 ±4
Popcorn65 ±5Sucrose65 ±4
Potato crisps56 ±3Glucose103 ±3
Soft drink/soda59 ±3Honey61 ±3
Rice crackers/crisps87 ±2
( ± ) represents Standard Deviation

the Gist

Glycemic Index (GI) is a measure that tells us the potential of a particular food to raise blood sugar levels. GI indicates the quality of carbohydrates. Low GI foods are high-quality carbohydrates whereas high GI foods are low-quality carbohydrates. 

Glycemic Load (GL) combines GI with the quantity of carbohydrates. 

Research indicates potential health benefits of low GI foods however the studies are not consistent. Therefore, GI or GL alone should not be considered when making food choices.