Practice Consideration
Glycemic Index
The glycemic index (GI) is a way of describing the rate at which a carbohydrate raises blood sugar levels in comparison to a reference standard.(1) High-GI foods raise blood glucose levels quickly, whereas those with a low GI break down more slowly, keeping blood glucose levels more stable.
For more information about the glycemic values of foods, visit the American Diabetes Association at www.diabetes.org and Sydney University’s online Glycemic Index database at www.glycemicindex.com. The current understanding of GI and glycemic control is that it is not necessary for people with diabetes to avoid all simple or added sugars. Many sugary foods have a moderate GI and do not adversely affect blood glucose levels. Simple sugars are found in many healthy foods such as fruit, milk, and yogurt and are, in fact, part of a balanced diet.(1,2)
Relationship Between Glycemic Index and Metabolic Outcomes
Both the Academy of Nutrition and Dietetics (2014) and the American Diabetes Association (2017) conducted systematic reviews on the use of GI in planning dietary intake to improve glycemic control. The results were equivocal.(3,4,5)
The 2014 study undertaken by the Academy of Nutrition and Dietetics reviewed research to characterize the relationship between GI and metabolic outcomes in people with type 1 and type 2 diabetes. In its 2015 Guideline the Academy confirmed its support for the statement that the results for the value of GI in dietary planning were equivocal.(6)
The three enquiries regarding GI (impact of differing GI on glycemia, insulin and CVD risk factors, impact on insulin levels, and relationship between GI and glycemia, insulin and CVD risk factors) were each assigned a “Grade II” level of support, indicating a finding of “fair” evidence to support the conclusion of an absence of effect on CVD risk factors, AIC, and of mixed evidence for an effect on insulin levels.(7) For the purposes of practitioners, their interpretation of the science is:
“If glycemic index or glycemic load is proposed as a glycemia-lowering strategy, the registered dietitian nutritionist (RDN) can advise adults with diabetes that lowering glycemic index or glycemic load may or may not have a significant effect on glycemic control. Studies longer than 12 weeks report no significant impact of glycemic index or glycemic load, independent of weight loss, on A1C. However, mixed results were reported regarding fasting glucose levels and endogenous insulin levels.”(4)
This recommendation for practitioners was listed as “conditional”, meaning that the dietitian must use their clinical judgment to determine whether using GI as a meal-planning tool is appropriate for the patient. The recommendation is not an “imperative” one for all patients.(8)
The American Diabetes Association reviewed the research and published a statement in January 2017, expressing concern that the research is not straightforward and that using GI and GL may or may not be of benefit:
“The literature concerning glycemic index and glycemic load in individuals with diabetes is complex, though in some studies lowering the glycemic load of consumed carbohydrates has demonstrated A1C reductions of 0.2 to 0.5% …” (5)
Overall Impact of Medical Nutrition Therapy
To put the potential use of GI dietary planning in context, the Academy of Nutrition and Dietetics evaluated the overall impact of medical nutrition therapy using a variety of approaches and reported that:
“Studies evaluating the effectiveness of Diabetes Medical Nutrition Therapy at three to six months reported reductions in HbA1c ranging from 0.25 percent to 2.9 percent.”
This is compared with the reported improvement attributed to using GI modification of 0.2 percent to 0.5 percent.(9)
The Canadian Diabetes Association Clinical Practice guideline includes a recommendation with “Grade B Level 2” evidence, for dietary advice emphasizing low-GI foods to help with glycemic control.(50,51) The guideline includes a second recommendation that alternative dietary patterns to that end include a Mediterranean-style, vegetarian or vegan dietary pattern, incorporating dietary pulses or DASH dietary pattern.(10)
References
1. Brand-Miller J, Foster-Powel K, Colaguiri S. The GI factor. Australia: Hodder & Stroughton; 1996.
2. Wheeler ML, Dunbar SA, Jaacks LM, Karmally W, Mayer-Davis EJ, Wylie-Rosett J, Yancy WS. Macronutrients, Food Groups, and Eating Patterns in the Management of Diabetes: A systematic review of the literature, 2010. Diabetes Care. 2012; 35: 434-445.
3. Academy of Nutrition and Dietetics. Diabetes Mellitus: Major Recommendations (2015); Accessed 11 August 2017. Available from: https://www.andeal.org/topic.cfm?menu=5305&cat=5597.
4. Academy of Nutrition and Dietetics. Diabetes Mellitus. Glycemic Index and Glycemic Load Recommendations Summary 2014.
Accessed 11 August 2017. Available from: https://www.andeal.org/template.cfm?template=guide_summary&key=4348.
5. American Diabetes Association. Lifestyle Management Diabetes Care. 2017; 40 (Suppl 1): S33-S43.
6. Academy of Nutrition and Dietetics. Recommendations Summary, Diabetes (DM) Type 1 and 2: Executive summary of recommendations. Accessed 11 August 2017. Available from: http://www.andeal.org/topic.cfm?cat=3252.
7. Academy of Nutrition and Dietetics. Diabetes Mellitus: Glycemic (2014); Accessed 02 August 2017.
Available from:www.andeal.org/topic.cfm?menu=5305&pcat=5488&cat=5025
8. Academy of Nutrition and Dietetics. Recommendations Summary, Diabetes (DM) Type 1 and 2: Executive summary of recommendations. Accessed 11 August 2017. Available from: http://www.andeal.org/topic.cfm?cat=3252.
9. Academy of Nutrition and Dietetics. Recommendations Summary, Diabetes (DM) Type 1 and 2: Medical Nutrition Therapy. 2017.
10. Dworatzek P, Arcudi K, Gougeon R. Canadian Diabetes Association. 2013 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada: Nutrition therapy. Can J Diabetes. 2013; 37: S61-S68.
| Classification | Glycemic Index Ranking |
| High | 70 or more |
| Moderate | 56 to 69 |
| Low | 0 to 55 |
For more information about the glycemic values of foods, visit the American Diabetes Association at www.diabetes.org and Sydney University’s online Glycemic Index database at www.glycemicindex.com. The current understanding of GI and glycemic control is that it is not necessary for people with diabetes to avoid all simple or added sugars. Many sugary foods have a moderate GI and do not adversely affect blood glucose levels. Simple sugars are found in many healthy foods such as fruit, milk, and yogurt and are, in fact, part of a balanced diet.(1,2)
Relationship Between Glycemic Index and Metabolic Outcomes
Both the Academy of Nutrition and Dietetics (2014) and the American Diabetes Association (2017) conducted systematic reviews on the use of GI in planning dietary intake to improve glycemic control. The results were equivocal.(3,4,5)
The 2014 study undertaken by the Academy of Nutrition and Dietetics reviewed research to characterize the relationship between GI and metabolic outcomes in people with type 1 and type 2 diabetes. In its 2015 Guideline the Academy confirmed its support for the statement that the results for the value of GI in dietary planning were equivocal.(6)
The three enquiries regarding GI (impact of differing GI on glycemia, insulin and CVD risk factors, impact on insulin levels, and relationship between GI and glycemia, insulin and CVD risk factors) were each assigned a “Grade II” level of support, indicating a finding of “fair” evidence to support the conclusion of an absence of effect on CVD risk factors, AIC, and of mixed evidence for an effect on insulin levels.(7) For the purposes of practitioners, their interpretation of the science is:
“If glycemic index or glycemic load is proposed as a glycemia-lowering strategy, the registered dietitian nutritionist (RDN) can advise adults with diabetes that lowering glycemic index or glycemic load may or may not have a significant effect on glycemic control. Studies longer than 12 weeks report no significant impact of glycemic index or glycemic load, independent of weight loss, on A1C. However, mixed results were reported regarding fasting glucose levels and endogenous insulin levels.”(4)
This recommendation for practitioners was listed as “conditional”, meaning that the dietitian must use their clinical judgment to determine whether using GI as a meal-planning tool is appropriate for the patient. The recommendation is not an “imperative” one for all patients.(8)
The American Diabetes Association reviewed the research and published a statement in January 2017, expressing concern that the research is not straightforward and that using GI and GL may or may not be of benefit:
“The literature concerning glycemic index and glycemic load in individuals with diabetes is complex, though in some studies lowering the glycemic load of consumed carbohydrates has demonstrated A1C reductions of 0.2 to 0.5% …” (5)
Overall Impact of Medical Nutrition Therapy
To put the potential use of GI dietary planning in context, the Academy of Nutrition and Dietetics evaluated the overall impact of medical nutrition therapy using a variety of approaches and reported that:
“Studies evaluating the effectiveness of Diabetes Medical Nutrition Therapy at three to six months reported reductions in HbA1c ranging from 0.25 percent to 2.9 percent.”
This is compared with the reported improvement attributed to using GI modification of 0.2 percent to 0.5 percent.(9)
The Canadian Diabetes Association Clinical Practice guideline includes a recommendation with “Grade B Level 2” evidence, for dietary advice emphasizing low-GI foods to help with glycemic control.(50,51) The guideline includes a second recommendation that alternative dietary patterns to that end include a Mediterranean-style, vegetarian or vegan dietary pattern, incorporating dietary pulses or DASH dietary pattern.(10)
References
1. Brand-Miller J, Foster-Powel K, Colaguiri S. The GI factor. Australia: Hodder & Stroughton; 1996.
2. Wheeler ML, Dunbar SA, Jaacks LM, Karmally W, Mayer-Davis EJ, Wylie-Rosett J, Yancy WS. Macronutrients, Food Groups, and Eating Patterns in the Management of Diabetes: A systematic review of the literature, 2010. Diabetes Care. 2012; 35: 434-445.
3. Academy of Nutrition and Dietetics. Diabetes Mellitus: Major Recommendations (2015); Accessed 11 August 2017. Available from: https://www.andeal.org/topic.cfm?menu=5305&cat=5597.
4. Academy of Nutrition and Dietetics. Diabetes Mellitus. Glycemic Index and Glycemic Load Recommendations Summary 2014.
Accessed 11 August 2017. Available from: https://www.andeal.org/template.cfm?template=guide_summary&key=4348.
5. American Diabetes Association. Lifestyle Management Diabetes Care. 2017; 40 (Suppl 1): S33-S43.
6. Academy of Nutrition and Dietetics. Recommendations Summary, Diabetes (DM) Type 1 and 2: Executive summary of recommendations. Accessed 11 August 2017. Available from: http://www.andeal.org/topic.cfm?cat=3252.
7. Academy of Nutrition and Dietetics. Diabetes Mellitus: Glycemic (2014); Accessed 02 August 2017.
Available from:www.andeal.org/topic.cfm?menu=5305&pcat=5488&cat=5025
8. Academy of Nutrition and Dietetics. Recommendations Summary, Diabetes (DM) Type 1 and 2: Executive summary of recommendations. Accessed 11 August 2017. Available from: http://www.andeal.org/topic.cfm?cat=3252.
9. Academy of Nutrition and Dietetics. Recommendations Summary, Diabetes (DM) Type 1 and 2: Medical Nutrition Therapy. 2017.
10. Dworatzek P, Arcudi K, Gougeon R. Canadian Diabetes Association. 2013 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada: Nutrition therapy. Can J Diabetes. 2013; 37: S61-S68.
Updated October 04, 2017