The glycemic index (GI) is a way to measure the impact specific types of food have on blood sugar. People are interested in understanding the glycemic index (and the glycemic load) of food so they can construct a healthier diet. Blood sugar affects many aspects of health, including the risk of getting cancer, cardiovascular disease, and diabetes, so watching the GI of foods in your diet can improve your overall health prospects.
GI values range from zero to one hundred. Food with a high GI value will make blood sugar levels rise (and fall) quickly, food with a low GI value will have a more slow and steady effect.
A GI value under 55 is low; foods that have a low GI value include beans, cruciferous vegetables, grapefruit, and tomatoes. A GI value between 56-69 is moderate; examples include pasta, green peas, sweet potatoes, orange juice, and blueberries. A GI value over 70 is high; examples include refined sugar, potatoes, white bread, dried fruit, carrots, and watermelon.
Why Are Glycemic Values Important?
Persons with diabetes struggle with maintaining balanced blood sugar. It’s a disease that’s reached epidemic proportions. Over 29 million Americans have diabetes, almost 90 million more are prediabetic. A diet centered around foods with a low GI value can help keep blood sugar under control.
You don’t have to suffer from diabetes to experience the benefits of regular, balanced blood sugar. Studies suggest consuming low GI food may help prevent cardiovascular disease and cancer; and that barely scratches the surface when considering the revelations uncovered by research into the effects of a low GI diet:
- A low GI diet may reduce the risk of type 2 diabetes.
- A high GI diet is associated with an increased risk of cardiovascular diseases.[6, 7]
- A study published in the American Journal of Clinical Nutrition in January 2016 suggests that following a high GI diet increases the risk of depression.
The Relationship Between Blood Sugar and Carbohydrates
Simple carbohydrates, also known as monosaccharides or disaccharides, are digested quickly and have an immediate effect on blood sugar. Common examples include refined sugar or high fructose corn syrup, as found in soft drinks. In general, foods high in simple carbohydrates have a high GI value.
Complex carbohydrates, also known as oligosaccharides and polysaccharides, are metabolized more slowly and do not have a dramatic effect on blood sugar. Foods high in complex carbohydrates include whole grain bread, vegetables, and legumes. Complex carbohydrates usually have a low GI value and, additionally, accompany other nutrients (such as fiber, vitamins, and minerals) that further reduce digestion time.
The Best Low Glycemic Index Foods
Below is a list of various foods and their GI value, as well as their glycemic load value–something we’ll cover shortly.
|Food||Glycemic Index (glucose = 100)||Total Serving Size (grams)||Glycemic Load Per Serving|
What Is Glycemic Load?
For example, carrots have a high GI value but a typical serving of carrots only contains about 6 grams of carbohydrates; probably not anywhere near enough to upset the blood sugar of the average person.
This is where glycemic load enters the picture. The glycemic load provides a more thorough consideration of the impact food has on blood sugar because it takes into account the GI value as well as the grams of carbohydrates (fat and protein are not considered as they do not affect blood sugar) in a serving.
Calculating Glycemic Load
Glycemic load is calculated by multiplying the GI value by the grams of carbohydrates in a serving and dividing by 100. A glycemic load value of 10 or less is low; 20 or above is high.
Watermelon, for example, has a GI value of 72 although a typical serving of watermelon only provides 6 grams of carbohydrates; a quick calculation reveals a glycemic load of less than 5.
A can of soda, on the other hand, may have a GI value of 65 but if a single can provides 40 grams of carbohydrates that means the glycemic load is 26, which is very high.
Is it any wonder that steady, daily consumption of soda and other sugary beverages contributes to so many health problems?
Factors That Affect Glycemic Index Values
Keep in mind that the GI value is just a starting point and can be affected by a number of factors. Processing and refining, for example, will result in a higher GI value. A whole baked potato has a lower GI value than instant mashed potatoes; processed orange juice has a higher GI value than fresh squeezed.
Eating different foods together can affect GI values. Research has shown that the negative effects of a high-carbohydrate diet are lessened when consumed with fiber. (Just to ensure there’s no confusion — no, eating a pound of lettuce won’t cancel out eating a pound of sugar.) The more ripe a fruit or vegetable, the higher its GI value. And, individual physiology–age, metabolism, health conditions–affect the way blood sugar is influenced.
Incorporating a Glycemic Diet Into Your Life
When constructing your diet, glycemic index and glycemic load values are great tools for guidance. Eating low-GI foods (and particularly those with low glycemic loads) is ideal for pregnant women, nursing mothers, diabetics, overweight individuals, and all people looking to improve their health, as long as you also use fundamentally sound principles of nutrition:
- Eat a variety of real, whole, organic food.
- Avoid junk food, refined sugar, and empty calories.
- If you splurge, do so in moderation.
- Quench your thirst with purified water.
Have you made a concerted effort to consume more low GI value foods and fewer high GI value foods? What tips can you share for designing a meal plan? What benefits have you noticed? Leave a comment below and share your thoughts with us.
- Brouns F, et al. “Glycaemic index methodology.” Nutr Res Rev. 2005;18(1),145-7.
- “Glycemic Index and Glycemic Load.” Oregon State University Micronutrient Center, Linus Pauling Institute. Oregonstate.edu. Accessed 17 Jul. 2018.
- “Glycemic Index and Diabetes.” American Diabetes Association. Accessed 17 Jul. 2018.
- Riccardi G, Rivellese AA. “Effects of dietary fiber and carbohydrate on glucose and lipoprotein metabolism in diabetic patients.” Diabetes Care. 1991;14(12):1115-25.
- Fletcher JA, et al. “The Second Meal Effect and Its Influence on Glycemia.” J Nutr Disord Ther. 1012;2:108.
- “Glycemic index and glycemic load for 100+ foods.” Harvard Health Publications. Harvard Medical School. 14 Mar. 2018. Accessed 17 Jul. 2018.
- “International Glycemic Index Database..” The University of Sydney. Updated 2 May 2017. Accessed 17 Jul. 2018.
- “International Glycemic Index Frequently Asked Questions (FAQs).” The University of Sydney. Updated 2 May 2017. Accessed 17 Jul. 2018.
- Jenkins DJA et al. “Glycemic index: overview of implications in health and disease.” Am J Clin Nutr, 2002;76:1(1),266S–273S.
- “New CDC report: More than 100 million Americans have diabetes or prediabetes [press release].” U.S. Centers for Disease Control and Prevention. 18 Jul. 2017.
- Livesey G, Taylor R, Livesey H, Liu S. “Is there a dose-response relation of dietary glycemic load to risk of type 2 diabetes? Meta-analysis of prospective cohort studies.” Am J Clin Nutr. 2013 Mar;97(3):584-96.
- Ma XY, et al. “Glycemic load, glycemic index and risk of cardiovascular diseases: meta-analyses of prospective studies.” Atherosclerosis. 2012;223(2),491-496.
- Dong JY, et al. “Meta-analysis of dietary glycemic load and glycemic index in relation to risk of coronary heart disease.” Am J Cardiol. 2012;109(11),1608-1613.
- Haghighatdoost F, et al. “Glycemic index, glycemic load, and common psychological disorders.” Am J Clin Nutr. 2016;103(1),201-209.