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You most likely have heard about the glycemic index, but may be wondering what it means or how to use it to improve your own health.

The glycemic index (GI) is a number describing a specific food’s ability to raise blood sugars for every 50 grams of carbohydrate consumed in relation to ingestion of 50 grams of straight glucose. It may seem like the glycemic index would be a simple tool to aid in blood sugar control, but interpreting a GI is a lot more complex than just shooting for a low score, like in a game of golf. There are many other factors that affect your blood sugar response.

First and foremost, it is important to note that the glycemic index is based off of 50 grams of carbohydrate from a specific food — not 50 grams of that food itself.

candy barFor example, if you have heard that whole grain bread has a higher glycemic index than a candy bar—it is often overlooked that it takes about 4 oz of whole grain bread (two of our big half inch slice breads) to get 50 grams of carbohydrate whereas it only takes a 2.5 oz Mars candy bar to get those 50 grams. Clearly, it takes a lot more bread to elicit a blood sugar response that is higher than the candy bar. The actual portion size makes a huge difference on the effect a food has on blood sugar. A high glycemic index food can still be healthy if eaten as a normal or smaller portion size.

Fat and protein are two more factors that impact blood sugar response, or the glycemic index. Fat hinders the enzymes that break down carbohydrates causing a delay in digestion and thus absorption of sugars. Protein also delays digestion. This ultimately results in a more gradual increase in blood sugars as opposed to a large spike. Again, another reason why candy bars or potato chips with high fat content can  have a lower glycemic index. This makes it quite evident that low glycemic index ignores the nutrient content of the foods themselves. Low glycemic foods don’t always translate into healthy foods.

It is also important to note that foods are seldom eaten alone, and again pairing a source of fat, protein, or even fiber can reduce the impact the carbohydrate has on blood sugar spikes. For example, a single piece of toast smeared with almond butter, or a roll with roasted turkey and a steamed vegetable will have a much lower glycemic index and effect on blood sugar than a candy bar would.

Other factors that can affect the glycemic response of a food are:

  • the ripeness of a food
  • how long it was cooked
  • the time of day the food was consumed
  • processing or preparation methods
  • plant varieties.

So how should you eat to control blood sugars if the glycemic index isn’t the best tool?

  1. Stick to whole foods (such as whole grains, nuts, seeds, legumes, fresh fruits and veggies) and limit refined foods with added sugars. Whole foods maintain their natural fiber content and will aid in delayed digestion, preventing spikes in blood sugar, all the while offering a wide array of nutrients.

    whole wheat bread
  2. Evenly space out your carbohydrate intake throughout the day by eating about every four hours in controlled portion sizes.
  3. Pair your carbohydrate with lean protein or healthy fats such as those that are from nuts, seeds, or oils that are liquid at room temperature which will slow the release of sugars into the blood stream.

Finally, remember everyone is a unique individual and body weight, blood volume, metabolism, and even medications among other things can affect your blood sugar as well, so carefully monitor and regulate how certain foods cause your blood sugar to react.


Interested in learning more from Melissa about whole grains? You can download her most recent nutrition guide here:


Download our eBook on Managing Your Diabetic Diet


Candy bar photo credit:  TheFoodJunk via photopincc


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Hi, I am Melissa! I’m a Registered, Licensed Dietitian and I have been the Nutrition Specialist for Great Harvest since December of 2010. I got my start in nutrition at Colorado State University where I graduated with a Bachelor of Science in Nutrition and Food Science with a focus in Dietetics. I went on to graduate from the Dietetic Internship Program at the Baptist Health System in San Antonio and then work as a Medical Nutrition Specialist in Houston. My love of the outdoors and the opportunity to work at one of Outside Magazine’s Top 100 Best Places to Work brought me to Montana and Great Harvest. My favorite part of my job is being able to work with an amazing group of fun and intellectual individuals who are passionate about making healthy eating a delicious experience while giving back to communities across the country.