Effects of Carbs, Protein and Fats on Glucose Levels

Understanding Food’s Impact on Glucose Levels

“How do I know if a meal or snack is going to spike up my glucose levels?”

“Why does it seem like every time I eat a carbohydrate (carbs), foods my glucose levels skyrocket?”

“Why is it that some foods make my glucose levels high and other foods don't?”

These are just a few examples of questions that many persons with diabetes ask themselves daily, and it can be extremely frustrating when there appears to be a lack of consistency in terms of what foods that we eat affect glucose levels.

When thinking about how to better understand a food’s impact on our glucose levels, it's best to start from the beginning. Let's talk about macronutrients: carbohydrates, protein, and fat. All foods are made up of one of or a combination of these three nutrients. It's important to understand how each one can impact glucose levels in order to make smart and educated choices when planning meals and snacks.

Carbohydrates supply the body's primary fuel or energy source, glucose. Think of glucose like the gas we put in our cars - it's what our bodies prefer to use for fuel! The two basic types of “carbs” are sugar and starches. Fiber is the third and will be discussed in more detail. (see How does Fiber Affect Glucose Levels?).

Most carbohydrate foods from 1-2 hours to be digested. Some carbs are digested quickly so that glucose can be used by the brain for energy. Carbs with more fiber are digested slower than carbs that do not contain adequate fiber. Choose foods with a high fiber content such as whole-grain cereals, bread and crackers; grains such as oats, barley, bulgur, and buckwheat; acorn and butternut squash; cooked peas, beans, and lentils; berries; and dried fruit and nuts.

Protein supplies the body with something called amino acids. Amino acids are building blocks to help build and repair body tissue. Your muscles, organs, bones, skin and many of the hormones in the body are made from protein. As a secondary role protein can also provide energy for your body if “carbs” are not available for fuel. However, proteins do not generally provide glucose when digested, so they have minimal impact on your glucose levels. Protein foods such as chicken, fish, eggs, cheese, nuts, nut butter, pumpkin seeds, can take anywhere from 3-4 hours to be digested- much slower than carbs.

Fat is the third group of foods that your body needs. That’s right – your body needs fat! Not all fat is bad. It is only when we eat too much fat or the wrong kind that it becomes a problem. Similar to protein, fat does not break down into glucose. Foods rich in dietary fat such as avocado, nuts, seeds like flaxseed or chia seed; Oils such as olive, canola, soybean, sunflower and peanut oils are all heart health. Fat slows down the digestive process resulting in a “delayed” rise in glucose levels as it takes a longer time to digest. Fat when eaten in modest amounts has a minimal impact on glucose levels, however eating too much fat can cause insulin resistance, which may lead to prolonged high glucose levels

So why am I outlining all of this? Because the combination of fiber-rich carbs + lean protein + heart-healthy fats can promote more stable glucose levels. Fiber, protein and fats help to slow down the digestion of carbs and delay their absorption into the blood. This helps to prevent spikes in glucose levels after eating.

Eating balanced meals and snacks can also help to give us a steady supply of glucose, our fuel source, throughout the day helping us feel more energized and more satisfied.

The Glycemic Response of Foods

Have you ever noticed that even though you carefully measure your “carb” servings or count your carbohydrate grams, you still cannot always explain your glucose level(s) after a meal?

The term we use to describe how quickly a “carb” breaks down and gets into the blood or the effect of the meal or snack you have had to eat is called the "glycemic response" of food, meal or snack.

A High glycemic response means that the glucose from the food or meal you have eaten enters the bloodstream rapidly. A low glycemic response means that the glucose enters the bloodstream slowly and steadily.

The following are a few examples of low glycemic meals and snacks:

• a slice of sprouted grain toast with 1/3 mashed avocado mashed and a fried egg
• a cup of blueberries on top of 6oz low-fat greek yogurt and a handful of nuts (almonds, cashews, walnuts)
• 4-5ozs. of lean protein (chicken, fish) with a cup of cooked barley, farro grain, quinoa, or beans and a side of non-starchy vegetables such as broccoli, cauliflower, salad with cucumber and tomato.

Choose high fiber carbs and pair them with lean protein foods and heart-healthy fats and see how your glucose levels respond!

To see your “glycemic response” of the food or meal you have eaten, monitor your glucose levels 2 hours after you eat and you will be able to see how your glucose levels respond!

Although this content is reviewed by Joslin Diabetes Center healthcare professionals, it is not intended to replace the medical advice of your doctor or healthcare provider. Please consult your healthcare provider for advice about a specific medical condition.