Type 2 Diabetes and Glycemic Index – Importance of a healthy diet in Diabetes

Type 2 diabetes usually develops gradually over several years, beginning when muscle and other cells stop responding to insulin. This condition, which is known as insulin resistance, causes sugar and insulin levels to remain high for longer periods after a meal.(1)
Over time, the increasing demands made on the insulin producing cells in the pancreas wears them out, and insulin production eventually stops.(1) So, foods that increase blood sugar levels by a large amount in a short span of time puts more stress on the body’s insulin production and can be detrimental in people with diabetes.
The glycemic index (GI) is a rating system for foods containing carbohydrates. It shows how quickly each food affects your blood sugar (glucose) level when that food is eaten on its own. The rating ranges from 0 to 100, with 100 representing the blood sugar rise when pure glucose is consumed.(2,3)

Low, medium & high GI

Foods can be classified into low glycemic index, medium glycemic index and high glycemic index in the following manner:(1)

  • Low-GI foods: Glycemic index < 55
  • Medium-GI foods: Glycemic index is 56-69
  • High -GI foods: Glycemic index is 70-100


A low glycemic index food will cause a slow, gradual increase in blood sugar levels and will maintain increased energy levels for a longer duration. A high glycemic index food will cause a quick upsurge in blood sugar levels, thus providing large amounts of energy for a short period of time. Foods with a high glycemic index, like white bread, are rapidly digested and cause substantial fluctuations in blood sugar. Foods with a low glycemic index, like whole oats, are digested more slowly, prompting a more gradual rise in blood sugar.(1,3)

Risks of a high glycemic index diet

A diet rich in high GI food can lead to increased risk for:

  • Type2 diabetes(4–8)
  • Heart disease(9–12)
  • Obesity/Overweight(8,12,13)


Some studies also show an increased risk for ovulatory infertility in women(14) and increased cancer risk (at several sites including colorectum, esophagus, lung, bladder, endometrium etc)(7,15,16).
A low dietary glycemic index diet also showed a decreased risk for clinical depression.(17)

Factors affecting the glycemic index

Many factors can affect a food’s glycemic index, including the following:

• Processing:

  • Milling and refining of grains – removing the bran and the germ – increases the glycemic index.(1)

• Physical form:

  • Finely ground grain is more quickly digested than coarsely ground grain.(1)
  • Eating whole grains like brown rice or oats is healthier than eating highly processed whole grain flour bread.(1)

• Cooking time:

  • Longer cooking times can lead to increase in GI.
  • For example, one study showed that regular rice which had a GI of 58 when cooked for 5 minutes, showed an increase to a GI of 83 when cooked for 15 minutes.(18)
  • A similar effect is seen with the cooking of kidney beans.(19)

• Fibre content:

  • High-fibre foods don’t contain as much digestible carbohydrate, so it slows the rate of digestion and causes a more gradual and lower rise in blood sugar.(1,20)

• Ripeness:

  • Ripe fruits and vegetables tend to have a higher glycemic index than un-ripened fruit.(1)

Recommendations on glycemic index for diabetics

So, how can glycemic index help diabetics and others lead a healthier lifestyle? The following are the findings and recommendations by the International Scientific Consensus Summit from the International Carbohydrate Quality Consortium (ICQC):

  • Having low GI foods will help reduce your post-meal (postprandial blood sugar)(21)
  • In general, having a low GI diet helps control your blood sugar in both Type 1 and Type 2 Diabetes.(21)
  • In diabetics, having a low GI diet will reduce the risk of heart disease, help weight management as well as decrease the risk of obesity, and help reduce generalized inflammation.(21)


How can you find the glycemic index of a food item?

If you want to know the Glycemic Index of a food item, the University of Sydney maintains a free, easily searchable database, where you can search for the glycemic index of 1000s of foods. The website can be accessed by clicking HERE.


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  4. Salmeron J, Ascherio A, Rimm EB, Colditz GA, Spiegelman D, Jenkins DJ, et al. Dietary Fiber, Glycemic Load, and Risk of NIDDM in Men. Diabetes Care. 1997 Apr 1;20(4):545–50.
  5. Krishnan S, Rosenberg L, Singer M, Hu FB, Djoussé L, Cupples LA, et al. Glycemic Index, Glycemic Load, and Cereal Fiber Intake and Risk of Type 2 Diabetes in US Black Women. Arch Intern Med. 2007 Nov 26;167(21):2304.
  6. Villegas R, Liu S, Gao Y-T, Yang G, Li H, Zheng W, et al. Prospective Study of Dietary Carbohydrates, Glycemic Index, Glycemic Load, and Incidence of Type 2 Diabetes Mellitus in Middle-aged Chinese Women. Arch Intern Med. 2007 Nov 26;167(21):2310.
  7. Sluijs I, van der Schouw YT, van der A DL, Spijkerman AM, Hu FB, Grobbee DE, et al. Carbohydrate quantity and quality and risk of type 2 diabetes in the European Prospective Investigation into Cancer and Nutrition–Netherlands (EPIC-NL) study. Am J Clin Nutr. 2010 Oct 1;92(4):905–11.
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  9. Beulens JWJ, de Bruijne LM, Stolk RP, Peeters PHM, Bots ML, Grobbee DE, et al. High Dietary Glycemic Load and Glycemic Index Increase Risk of Cardiovascular Disease Among Middle-Aged Women. J Am Coll Cardiol. 2007 Jul;50(1):14–21.
  10. Halton TL, Willett WC, Liu S, Manson JE, Albert CM, Rexrode K, et al. Low-Carbohydrate-Diet Score and the Risk of Coronary Heart Disease in Women. N Engl J Med. 2006 Nov 9;355(19):1991–2002.
  11. Evans CE, Greenwood DC, Threapleton DE, Gale CP, Cleghorn CL, Burley VJ. Glycemic index, glycemic load, and blood pressure: a systematic review and meta-analysis of randomized controlled trials. Am J Clin Nutr. 2017 May;105(5):1176–90.
  12. Maki KC, Rains TM, Kaden VN, Raneri KR, Davidson MH. Effects of a reduced-glycemic-load diet on body weight, body composition, and cardiovascular disease risk markers in overweight and obese adults. Am J Clin Nutr. 2007 Mar;85(3):724–34.
  13. Ebbeling CB, Leidig MM, Feldman HA, Lovesky MM, Ludwig DS. Effects of a Low–Glycemic Load vs Low-Fat Diet in Obese Young Adults: A Randomized Trial. JAMA. 2007 May 16;297(19):2092.
  14. Chavarro JE, Rich-Edwards JW, Rosner BA, Willett WC. A prospective study of dietary carbohydrate quantity and quality in relation to risk of ovulatory infertility. Eur J Clin Nutr. 2009 Jan;63(1):78–86.
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  16. Sieri S, Agnoli C, Pala V, Grioni S, Brighenti F, Pellegrini N, et al. Dietary glycemic index, glycemic load, and cancer risk: results from the EPIC-Italy study. Sci Rep. 2017 Dec;7(1):9757.
  17. Rahimlou M, Morshedzadeh N, Karimi S, Jafarirad S. Association between dietary glycemic index and glycemic load with depression: a systematic review. Eur J Nutr. 2018 Oct;57(7):2333–40.
  18. Kaur B, Ranawana V, Henry J. The Glycemic Index of Rice and Rice Products: A Review, and Table of GI Values. Crit Rev Food Sci Nutr. 2016 Jan 25;56(2):215–36.
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