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Glycemic Index and Glycemic Load

Prevention is better than cure

Photo by Mali Maeder from Pexels
Photo by Mali Maeder from Pexels

The Glycemic Index (GI) and Glycemic Load (GL) are tools developed by nutrition scientists to help us make healthy food choices.

They rank foods according to their carbohydrate content and how quickly those carbs raise our blood sugar levels. This is important because foods causing sudden blood-sugar spikes increase our risk of serious illness and premature death.

Both GI and GL are useful to those suffering from diabetes and obesity, but also to healthy individuals who want to maintain their health. 

Just keep in mind that these rankings are based on carbohydrate content only and give no information about other valuable nutrients like fats, protein, or vitamins.  

 

Carbohydrates and health

Carbohydrates are vital nutrients that provide us with energy to survive and function. Without them, it isn’t possible to move, think, or even breathe.

But they are not all made equal.

There are two types of carbs in food: simple and complex.

Simple carbs are unhealthy because we can digest them easily to obtain energy. They release fast loads of glucose and cause sudden spikes in our blood sugar levels.

These bad carbs are generally present in highly-processed foods

Research has shown that the excessive intake of simple carbs increases the risk of:

  • Type 2 diabetes [1]
  • Heart disease, including stroke and heart attack [2]
  • Weight gain and obesity [3]
  • Colorectal cancer [4]

On the other hand, complex carbs are extremely healthy. They release sugars in a controlled way, regulate the speed of digestion, and normalize our bowel movements.

These good carbs are abundant in unprocessed foods like fruits, veggies, and whole grains.

 

Glycemic Index

The glycemic index (GI) is a measure of how quickly a food raises the blood levels of glucose. 

  • Pure glucose is used as a reference and assigned a value of 100. Other foods are ranked on a scale from 1 to 100 in relation to pure glucose. 
  • The lower the GI of a food, the slower the sugar release into the bloodstream. In other words, the lower the GI, the healthier the food.

Here’s the GI of some common foods. For good carbs, we should aim for low and medium GI [5].

Low GI (below 55)

  • Milk
  • Soy milk
  • Non-flavored yogurt
  • Dark chocolate
  • Whole grains: oats, barley, wild rice
  • Legumes: peanuts, beans, peas
  • Seeds: sunflower, pumpkin, sesame
  • Nuts: almonds, cashews
  • Non-starchy vegetables
  • Most fruits

Medium GI (56-69)

  • White sugar (sucrose)
  • Honey
  • Ice cream
  • Whole-grain bread
  • Sweet potato
  • Raisins
  • Pineapple
  • Watermelon
  • Mango
  • Banana

High GI (70-100)

  • White rice
  • Corn flakes
  • White bread
  • Congee
  • Instant mashed potato
  • Instant oat porridge
  • Rice milk
  • Soft drinks
  • Any foods containing high-glucose or high-fructose corn syrup
  • Most processed foods

→ Note 1: the GI values change when you mix foods. If you eat something high-GI, combine it with low GI foods to regulate your blood sugar levels.

→ Note 2: Keep in mind that riper fruits will have higher GI values.

 

Glycemic Load

One limitation to the GI ranking is that it doesn’t tell us how quickly A PORTION of food raises our blood sugar levels. It just ranks the food as a whole.

But it certainly should matter if we eat one cookie or the whole bag, right?

That’s when the Glycemic Load (GL) comes in handy. It was developed to take into account both the GI and the portion size with this simple formula: 

Glycemic Load = GI x grams of carbs per portion ÷ 100

  • The lower the GL, the better.

This means that the carbs load in that portion will have a lighter impact on your blood sugar.

This means that food with a high GI (bad GI score) becomes healthier by just reducing the portion size [6].

  • Aim for low to medium GL for good health.

Low GL score: below 10.
Medium GL score:  11 to 19.
High GL score: 20 or above
[6]

Here are some examples of why portion size matters:

FoodGlycemic Index (GI) [7]Portion sizeGlycemic Load (GL)
Apple36 (low)1 unit, medium size7 (low)
2 units, medium size14 (medium)
Watermelon76 (high)100 g6 (low)
200 g 12 (medium)
Banana56 (medium)1 unit, large15 (medium)
½  unit, large7 (low)
White rice, boiled73 (high)200 g39 (high)
100 g18 (medium)
White bread75 (high)1 slice (30 g)11 (medium)
2 slices (60 g)22 (high)
Ice cream58 (medium)1 scoop (65 g)10 (medium)
2 scoops (130 g)20 (high)
Coca-cola62 (medium)1 bottle (500 mL)33 (high)
1 can (355 mL)24 (high)
Cornflakes81 (high)1 cup (30 g)20 (high)
½ cup (15 g)10 (low)
Oreos64 (medium)1 cookie (11 g)5 (low)
4-cookie pack20 (high)

 

The bottom line

The Glycemic Index and Glycemic Load are useful tools to help us make healthy food choices

However, unless you need to undergo a very strict diet for the management of diabetes or any other illness, you shouldn’t focus so much on the numbers as on the quality of your food. 

  • Wholesome, unprocessed foods that are rich in fiber, are the healthiest for our blood sugar levels. You should, therefore, include more fruits, vegetables, whole grains, nuts, seeds, and legumes in your meals. 
  • Watch the portions. Remember that the impact of many foods on your blood sugar levels depends on how much you’re eating.
  • Don’t forget to consider other nutrients (fats, protein, vitamins) to decide if a food is good for you. GI and GL values refer only to the carbohydrate content of food.

Low-glycemic recommendations for you

  1. de Munter JSL, Hu FB, Spiegelman D, Franz M, van Dam RM. Whole grain, bran, and germ intake and risk of type 2 diabetes: a prospective cohort study and systematic review. PLoS Med. 2007;4: e261.
  2. Halton TL, Willett WC, Liu S, Manson JE, Albert CM, Rexrode K, et al. Low-carbohydrate-diet score and the risk of coronary heart disease in women. N Engl J Med. 2006;355: 1991–2002.
  3. Maki KC, Rains TM, Kaden VN, Raneri KR, Davidson MH. Effects of a reduced-glycemic-load diet on body weight, body composition, and cardiovascular disease risk markers in overweight and obese adults. Am J Clin Nutr. 2007 Mar; 85(3):724-34.
  4. Higginbotham S, Zhang Z-F, Lee I-M, Cook NR, Giovannucci E, Buring JE, et al. Dietary glycemic load and risk of colorectal cancer in the Women’s Health Study. J Natl Cancer Inst. 2004;96: 229–233.
  5. Wikipedia. https://en.wikipedia.org/wiki/Glycemic_index
  6. Harvard Health Publishing. Carbohydrates and Blood Sugar. https://www.hsph.harvard.edu/nutritionsource/carbohydrates/carbohydrates-and-blood-sugar/
  7. Harvard Health Publishing. Glycemic index for 60+ foods. https://www.health.harvard.edu/diseases-and-conditions/glycemic-index-and-glycemic-load-for-100-foods/

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