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No ‘Bad’ Foods: Understanding the Glycemic Index and How to Use It

September 14, 2022

Back in the ’90s there was a lot of scare talk about “deadly whites:” sugar, white flour, rice, potatoes — you get the idea. Today, dietitians reject the notion that there are “good” and “bad” foods.

High-glycemic foods – those with a lot of carbs or sugar -- can be part of a balanced diet, although if you’re managing diabetes or heart disease, you might need a little more information about how to do that.

What Is Blood Sugar?

Blood sugar and blood glucose are interchangeable terms. When we eat a carbohydrate — cereal, pasta, fruit — our digestive system breaks that down to glucose, which travels through the blood stream, delivering the energy that allows us to function.

What Happens When Blood Sugar Jumps?

When blood sugar is elevated, it produces a hormonal effect, releasing the insulin that allows us to process that glucose. A lot of factors contribute to how high and how fast blood sugar can rise, including not just what we’re eating but how much, and in what combinations. Pairing carbs with fat, protein and fiber will slow down the process of digestion and the release of glucose.

What Is the Glycemic Index?

Developed to help people with diabetes make better food choices, the international glycemic index is maintained by Sydney University in Sydney, Australia. Index numbers are assigned based on how much a given food raises blood sugar compared to how much pure glucose does the same thing.

Glycemic Index vs. Glycemic Load

Glycemic index numbers aim to tell you how high a particular food will raise your blood glucose. But indexes don’t give any information on quantity or about the nutritional value of a food. For example, watermelon has a high GI of 80, but watermelon doesn’t have many carbs per serving — you would have to eat an awful lot of watermelon to raise your blood sugar quickly.

To help make the index more meaningful, researchers developed the idea of glycemic “load.” This takes into account not only the index number but typical serving sizes, so you can see that if you eat a reasonable amount of a particular food, the load might not be very high, even if the index number is. Considering the GI “load” makes the index more user-friendly and helps avoid eliminating healthy foods.

Using the Index to Help Manage Diabetes and Heart Disease

Diets heavy in high-glycemic foods generally do not keep us as satisfied as a balanced approach that includes protein, fat, carbs and fiber. If we’re eating even what we call a healthy food — say, a fruit — but we’re not having that combined with a fat or a protein, it’s going to be digested quickly. Insulin shoves the energy into our cells, but we’ll be hungry again very soon. When what we are eating doesn’t keep us full, overeating becomes a problem.

Chronic overeating, especially high carbohydrate foods, an inactive lifestyle and family history can increase our risk of insulin resistance. With insulin resistance, our cells don’t respond as well to the insulin that our body is producing, so blood sugar becomes elevated. This puts people at higher risk of developing diabetes and heart disease.

Is There an Easier Way to Think About This?

While the glycemic index offers a lot of useful information, it can be hard to use as a guide to daily food intake. A simpler way to achieve the same results is to make sure you are consuming a range of foods, if not at every meal then every day or over the course of a week. When you think about meal planning:

  • Choose something from each food group.
  • Choose foods in an array of colors, which tend to be high in the nutrients we need.
  • Use the “80/20 rule” — make 80 percent of your food choices something you like that also benefits the body. The other 20 percent? Choose foods you like the taste of and are excited about eating.

The easiest way to look at it is, consider your whole plate, not just one food. If you’re having a high-GI food like a banana, can you add a piece of whole grain bread? Perhaps with some peanut butter? Now you have a balanced plate, thereby lowering the overall GI impact of the meal or snack.

The Bottom Line

Focusing too closely on details like GI numbers can take the fun out of eating, which won’t help you maintain a healthy diet. It’s not realistic to think you can meet every macronutrient need in every meal. Instead look at the overall picture. Over a day, or a week, are you meeting your nutritional needs? Focusing less on rules and listening more to our bodies as we strive for balance is a better path to healthful, guilt-free choices.

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