Glycemic Index and Diabetes

Glycemic Index and Diabetes

What Is Glycemic Index? 

The glycemic index (GI) ranks a carbohydrate containing food based on how much it raises postprandial blood glucose levels in comparison with reference food (ie, white bread or pure glucose).1,2 The GI is on a scale of 1 to 100: low GI is <55, moderate GI is 56-69, and high GI is >69. Foods with slower absorption and digestion have a low GI while foods with rapid absorption and digestion have high GI.3 Various factors such as macronutrients consumed in conjunction and cooking methods can affect the GI of a food.4


What Is Glycemic Load? The glycemic load (GL) of a food multiplies the GI by the total available carbohydrate content (g) in the serving divided by 100.1,4 This measurement is used to assess a food’s overall effect on blood glucose and insulin levels.


What Are Low & High Glycemic Index Foods?

 Examples of low-GI foods include:1,4,5

  • Whole grains
  • Nuts
  • Legumes (eg, chickpeas, kidney beans, lentils)
  • Fruits (eg, apples, oranges, peaches)
  • Non-starchy vegetables (eg, broccoli, cucumber, celery, carrots)


Examples of high-GI foods include:

  • Sugary foods (eg, soft drinks, candies, cookies)
  • White bread
  • White rice
  • Potato


What Are the Benefits of Low Glycemic Index on Diabetes?

Current guidelines heavily emphasize the importance of intensive lifestyle management as a fundamental aspect of diabetes care.6,7 Lifestyle management of diabetes includes healthy eating patterns that can facilitate glycemic control and healthy weight loss. Studies are showing that a low glycemic load dietary pattern may have beneficial effects in achieving glycemic control in individuals with diabetes by improving their carbohydrate quality and quantity.1

As individuals with prediabetes, type 1 diabetes mellitus (T1DM), and type 2 diabetes mellitus (T2DM) have diminished or no ability to control postprandial blood glucose levels without medical care, low-GI diets that have lower postprandial blood glucose excursions have shown to improve glucose control in diabetic individuals.8

Several recent systematic reviews and meta-analyses have demonstrated that low-GI diets are effective in improving various parameters of diabetes.1,8–10 A 2018 review of 6 randomized controlled trials (RCTs) studying the effect of dietary GI in adults with T2DM found that low-GI diets were more effective in improving hemoglobin (Hb) A1c and fasting blood glucose levels than high-GI diets.10 Similarly, a 2019 review of 54 RCTs on low-GI diets in adults and children with T1DM or T2DM concluded that low-GI diets effectively lowered HbA1c and fasting glucose levels, with reduction in their levels being inversely correlated with body weight.8 The study also found improvements in body mass index (BMI), low-density lipoprotein (LDL) cholesterol, and total cholesterol levels. Most recently, a 2021 review of 29 RCTs on the effects of low-GI diets on cardiometabolic factors in adults with type 1 or 2 diabetes found small but significant improvements in HbA1c, fasting glucose, LDL cholesterol, triglycerides, BMI, and systolic blood pressure.1

Despite none of these studies finding improvements in blood insulin or insulin resistance, the favorable outcomes in HbA1c, fasting glucose, and BMI show that low-GI diets may be useful for diabetes management.1,8,10 Some of these outcomes show very modest improvements, but even small improvements in these numbers can result in clinically significant benefits. For instance, studies have shown that a 1% and 0.67% reduction in HbA1c levels resulted in a respective 37% and 21% reduction in diabetes-related microvascular complications.11,12 The US Food and Drug Administration has also recognized a 0.3-0.4% reduction in HbA1c as clinically significant for pharmaceutical treatments for diabetes.13 As such, even small improvements in HbA1c levels and potentially other parameters from low-GI diets may result in clinical value in diabetes management.


1. Chiavaroli L, Lee D, Ahmed A, et al. Effect of Low Glycaemic Index or Load Dietary Patterns on Glycaemic Control and Cardiometabolic Risk Factors in Diabetes: Systematic Review and Meta-Analysis of Randomised Controlled Trials. BMJ. 2021;374:n1651. doi:10.1136/bmj.n1651
2. Esfahani A, Wong JMW, Mirrahimi A, Srichaikul K, Jenkins DJA, Kendall CWC. The Glycemic Index: Physiological Significance. J Am Coll Nutr. 2009;28(sup4):439S-445S. doi:10.1080/07315724.2009.10718109
3. Dominiczak M, Logue J. Nutrients and Diets, Chapter 32. In: Baynes J, ed. Medical Biochemistry. Elsevier; 2022:471-487.
4. Gray A, Threlkeld RJ. Nutritional Recommendations for Individuals with Diabetes. In: Feingold KR, Anawalt B, Blackman MR, et al., eds. Endotext., Inc.; 2000. Accessed February 15, 2023.
5. Atkinson FS, Foster-Powell K, Brand-Miller JC. International Tables of Glycemic Index and Glycemic Load Values: 2008. Diabetes Care. 2008;31(12):2281-2283. doi:10.2337/dc08-1239
6. American Diabetes Association. Standards of Medical Care in Diabetes—2022 Abridged for Primary Care Providers. Clinical Diabetes. 2022;40(1):10-38. doi:10.2337/cd22-as01
7. American Diabetes Association. 5. Lifestyle Management: Standards of Medical Care in Diabetes—2019. Diabetes Care. 2018;42(Supplement_1):S46-S60. doi:10.2337/dc19-S005
8. Zafar MI, Mills KE, Zheng J, et al. Low-Glycemic Index Diets as an Intervention for Diabetes: A Systematic Review and Meta-Analysis. Am J Clin Nutr. 2019;110(4):891-902. doi:10.1093/ajcn/nqz149
9. Jenkins DJA, Kendall CWC, McKeown-Eyssen G, et al. Effect of a Low–Glycemic Index or a High–Cereal Fiber Diet on Type 2 Diabetes: A Randomized Trial. JAMA. 2008;300(23):2742-2753. doi:10.1001/jama.2008.808
10. Ojo O, Ojo OO, Adebowale F, Wang XH. The Effect of Dietary Glycaemic Index on Glycaemia in Patients with Type 2 Diabetes: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Nutrients. 2018;10(3):373. doi:10.3390/nu10030373
11. UK Prospective Diabetes Study (UKPDS) Group. Intensive Blood-Glucose Control With Sulphonylureas or Insulin Compared With Conventional Treatment and Risk of Complications in Patients With Type 2 Diabetes (UKPDS 33). Lancet. 1998;352(9131):837-853.
12. ADVANCE Collaborative Group, Patel A, MacMahon S, et al. Intensive Blood Glucose Control and Vascular Outcomes in Patients with Type 2 Diabetes. N Engl J Med. 2008;358(24):2560-2572. doi:10.1056/NEJMoa0802987
13. US Food and Drug Administration. Guidance for Industry: Diabetes Mellitus: Developing Drugs and Therapeutic Biologics for Treatment and Prevention. Released February 13, 2008. Accessed February 21, 2023.



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