Choosing the Right Food (Part 1)

Glycemic Index & Glycemic Load

The Glycemic Index (GI) is a relative ranking of carbohydrate foods on how much they affect blood glucose levels. After eating 50g of the food, blood glucose is measured every 15 minutes for 2 hours. Higher GI foods cause a greater increase in blood sugar after eating. As a standard, the GI of 50g glucose is 100. GI above 70 is considered high, between 56 - 69 is medium, and GI below 55 is low. The GI of steamed white rice is 70, whereas steamed barley is 35, and the GI of rice porridge is 93 [1]. This means rice porridge can increase blood sugar similarly to ingesting pure glucose.

As high GI foods increase blood sugar levels more, they also cause insulin levels to rise more [2,3]. High GI is associated with higher insulin resistance and metabolic syndrome [4,5], and lower GI-diets have been shown to recover insulin sensitivity [6,7]. In some people without diabetes, researchers have found that insulin causes increased hunger and overeating [8]. In addition, insulin blocks fat burning. These may contribute to obesity, another reason to avoid high insulin, blood sugar spikes and high GI food.

Glycemic Load (GL), like GI, measures the increase in blood sugar, but for a regular serving size of the food instead of 50g. In our daily lives, we may not consume 50g of sugar in a meal, but we may eat 45g of cereal. Because of this, GL is a more practical guideline for choosing carbohydrate foods. A GL of 20 or above is considered high, between 11 – 19 is medium, and 10 or below is low.

GI-GL.png

Choosing the right food

GI and GL are important factors to consider for diabetic-friendly diets. But blood sugar levels are also dependent on the content of other materials such as fiber, minerals and water, as well as the cooking method and eating habits.

Fruits with a lot of fiber and density that need to be chewed more, such as apples, generally cause a lower sugar spike than juicier fruits such as oranges and grapes. Even when they contain the same ingredient, liquid foods such as juices and soups cause a faster increase in blood sugar and are not favorable for blood sugar levels. Porridge is good for digestion, but they are quickly converted to sugars in the body. Eating more fibers has also been associated with lower prevalence of metabolic syndrome [9]. Some high-fiber foods include apple, onion, seaweed, barley, blueberry, chicory root and lentils.

Boiled potatoes and fried potatoes also have different effects on blood sugar. When potatoes are heated, the carbohydrates inside turn into simple sugars (maltose), and when roasted, the water evaporates from the potato, leaving a higher concentration of sugars inside so that its effect is similar to eating sugar cubes. Fried potatoes, on the other hand, mix oils with carbohydrates, making it more difficult to digest, hence causing a slower increase in blood sugar levels. However, it must be noted that fried potatoes have a much higher AGE content, which contributes to insulin resistance and weight gain. Therefore it is advisable to avoid potatoes, sweet potatoes and other high-carb ingredients altogether.

For grains, unprocessed and whole grains are recommended for blood glucose management [10,11]. Brown rice, which is a whole grain with the hull intact, is digested slower than refined white rice. Bread made with whole-wheat (whole meal) flour, that contains all parts of the grain, is also preferable to refined white flour. Whole grain diets also have high fiber contents, and have been shown to lower inflammation and body weight [12].

Summary​​

  • Use glycemic load (GL) to avoid foods that cause dramatic increases in blood sugar

  • Choose high-fiber, low-carb foods

  • Replace white carbs with whole grains

 

Sources:

  1. https://dx.doi.org/10.1017/S0007114518003446

  2. https://dx.doi.org/10.1093/ajcn/34.3.362

  3. https://dx.doi.org/10.1093/ajcn/76.1.5

  4. https://dx.doi.org/10.2337/diacare.27.2.538

  5. https://dx.doi.org/10.1079/BJN2002769

  6. https://dx.doi.org/10.1079/BJN2002789

  7. https://dx.doi.org/10.1016/s0026-0495(96)90129-8

  8. https://dx.doi.org/10.1037/0278-6133.4.1.1

  9. https://dx.doi.org/10.1371/journal.pmed.0040261

  10. https://dx.doi.org/10.1136/gutjnl-2017-314786

  11. https://dx.doi.org/10.1016/j.jada.2010.03.018

  12. https://dx.doi.org/10.1007/s11892-013-0453-1

  13. GL foods list: https://www.glycemicindex.com/