Glycemic index

The glycemic index of a food is defined as the incremental area under the two-hour blood glucose response curve (AUC) following a 12-hour fast and ingestion of a food with a certain quantity of available carbohydrate (usually 50 g). The AUC of the test food is divided by the AUC of the standard (either glucose or white bread, giving two different definitions) and multiplied by 100. The average GI value is calculated from data collected in 10 human subjects. Both the standard and test food must contain an equal amount of available carbohydrate. The result gives a relative ranking for each tested food.{{cite journal |vauthors=Brouns F, Bjorck I, Frayn KN, etal |title=Glycaemic index methodology |journal=Nutr Res Rev |volume=18 |issue=1 |pages=145–71 |date=June 2005 |pmid=19079901 |doi=10.1079/NRR2005100 |doi-access=free }}

Foods with carbohydrates that break down quickly during digestion and release glucose rapidly into the bloodstream tend to have a high GI; foods with carbohydrates that break down more slowly, releasing glucose more gradually into the bloodstream, tend to have a low GI.

A lower glycemic index suggests slower rates of digestion and absorption of the foods' carbohydrates and can also indicate greater extraction from the liver and periphery of the products of carbohydrate digestion.{{citation needed|date=May 2022}}

The current validated methods use glucose as the reference food, giving it a glycemic index value of 100 by definition. This has the advantages of being universal and producing maximum GI values of approximately 100. White bread can also be used as a reference food, giving a different set of GI values (if white bread = 100, then glucose ≈ 140). For people whose staple carbohydrate source is white bread, this has the advantage of conveying directly whether replacement of the dietary staple with a different food would result in faster or slower blood glucose response. A disadvantage with using white bread as a reference food is that it is not a well-defined reference: there is no universal standard for the carbohydrate content of white bread.{{cn|date=January 2025}}

Glycemic index charts often give only one value per food, but variations are possible due to:

• Ripeness — riper fruits contain more sugars, increasing GI
• Cooking methods — the more cooked, or overcooked, a food, the more its cellular structure is broken, with a tendency for it to digest quickly and raise blood glucose more
• Processing — e.g., flour has a higher GI than the whole grain from which it is ground as grinding breaks the grain's protective layers and the length of storage. Potatoes are a notable example, ranging from moderate to very high GI even within the same variety.{{cite web|url=http://ziag4.mmb.usyd.edu.au/FMPro?-db=gidb2.fp5&-format=resultsv4a.htm&-lay=tableview&-sortfield=none&-sortorder=descend&FoodName=potato&-max=20&-skip=20&-find= |title=GI Database |access-date=2012-08-01 |url-status=dead |archive-url=https://web.archive.org/web/20090215175517/http://ziag4.mmb.usyd.edu.au/FMPro?-db=gidb2.fp5&-format=resultsv4a.htm&-lay=tableview&-sortfield=none&-sortorder=descend&FoodName=potato&-max=20&-skip=20&-find= |archive-date=February 15, 2009 }}
• Consumption order — changing the order that foods are eaten was demonstrated to affect blood glucose levels, where eating starches or sugars first resulted in faster increases than when eaten after the rest of the meal{{cite journal |last1=Shukla |first1=Alpana P. |last2=Iliescu |first2=Radu G. |last3=Thomas |first3=Catherine E. |last4=Aronne |first4=Louis J. |title=Food Order Has a Significant Impact on Postprandial Glucose and Insulin Levels |journal=Diabetes Care |date=1 July 2015 |volume=38 |issue=7 |pages=e98–9 |doi=10.2337/dc15-0429 |pmid=26106234 |pmc=4876745 }}

More importantly, the glycemic response is different from one person to another, and also in the same person from day to day, depending on blood glucose levels, insulin resistance, and other factors.{{cite journal|last=Freeman|first=Janine|title=The Glycemic Index debate: Does the type of carbohydrate really matter?|url=http://www.diabetes.org/glycemic-index.jsp |archive-url=https://web.archive.org/web/20070214135006/http://www.diabetes.org/glycemic-index.jsp|archive-date=February 14, 2007|date=September 2005|journal=Diabetes Forecast}}

The glycemic index only indicates the impact on glucose level two hours after eating the food. People with diabetes have elevated levels for four hours or longer after eating certain foods.

GI values can be interpreted intuitively as percentages on an absolute scale and are commonly interpreted as follows:

A low-GI food will cause blood glucose levels to increase more slowly and steadily, which leads to lower postprandial (after meal) blood glucose readings. A high-GI food causes a more rapid rise in blood glucose level and is suitable for energy recovery after exercise or for a person experiencing hypoglycemia.{{cn|date=January 2025}}

The glycemic effect of foods depends on various factors, such as the type of starch (amylose versus amylopectin), physical entrapment of the starch molecules within the food, fat and protein content of the food and organic acids or their salts in the meal.{{cite journal|last1=Kirpitch|first1=A. R.|last2=Maryniuk|first2=M. D.|title=The 3 R's of Glycemic Index: Recommendations, Research, and the Real World|journal=Clinical Diabetes|volume=29|issue=4|year=2011|pages=155–59|issn=0891-8929|doi=10.2337/diaclin.29.4.155|url=http://clinical.diabetesjournals.org/content/29/4/155.full|doi-access=free|access-date=2015-12-14|archive-date=2015-12-22|archive-url=https://web.archive.org/web/20151222100556/http://clinical.diabetesjournals.org/content/29/4/155.full|url-status=live|url-access=subscription}} The presence of fat or soluble dietary fiber can slow the gastric emptying rate, thus lowering the GI. In general, coarse, grainy breads with higher amounts of fiber have a lower GI value than white breads.{{cite book |title=Glycemic Index: From Research to Nutrition Recommendations? |publisher=Nordic Council of Ministers |location=Copenhagen |year=2005 |isbn=978-92-893-1256-1 |url=http://www.norden.org/en/publications/publikationer/2005-589 |id=TemaNord2005:589 |access-date=2012-08-01 |archive-url=https://web.archive.org/web/20131227112656/http://www.norden.org/en/publications/publikationer/2005-589 |archive-date=2013-12-27 |url-status=dead }}{{cite journal |vauthors=Atkinson FS, Foster-Powell K, Brand-Miller JC |title=International tables of glycemic index and glycemic load values: 2008 |journal=Diabetes Care |volume=31 |issue=12 |pages=2281–83 |date=December 2008 |pmid=18835944 |pmc=2584181 |doi=10.2337/dc08-1239 }}

Many modern diets rely on the glycemic index, including the South Beach Diet, Transitions by Market America and NutriSystem Nourish Diet.{{cite web|url=http://www.nutrisystem.com/nourishprogram/gichart.cfm |title=Nutrisystem |date=2008-03-06 |access-date=2012-08-01 |url-status=dead |archive-url=https://web.archive.org/web/20080506203813/http://www.nutrisystem.com/nourishprogram/gichart.cfm |archive-date=May 6, 2008 }} However, others have pointed out that foods generally considered to be unhealthy can have a low glycemic index, for instance, chocolate cake (GI 38), ice cream (37), or pure fructose (19), whereas foods like potatoes and rice have GIs around 100 but are commonly eaten in some countries with low rates of diabetes.{{cite journal |vauthors=Foster-Powell K, Holt SH, Brand-Miller JC |title=International table of glycemic index and glycemic load values: 2002 |journal=Am. J. Clin. Nutr. |volume=76 |issue=1 |pages=5–56 |date=July 2002 |pmid=12081815 |doi=10.1093/ajcn/76.1.5 |doi-access=free }}

Dietary replacement of saturated fats by carbohydrates with a low glycemic index may be beneficial for weight control, whereas substitution with refined, high glycemic index carbohydrates is not.{{cite journal |vauthors=Brand-Miller J, Buyken AE |title=The glycemic index issue |journal=Curr. Opin. Lipidol. |volume=23 |issue=1 |pages=62–67 |year=2012 |pmid=22157060 |doi=10.1097/MOL.0b013e32834ec705 |s2cid=205829601 |url=https://zenodo.org/record/895683 |access-date=2019-06-27 |archive-date=2020-09-25 |archive-url=https://web.archive.org/web/20200925042210/https://zenodo.org/record/895683 |url-status=live }} However, a 2023 Cochrane review did not find that adoption of low glycemic index (or load) diets by people who are overweight or obese leads to more weight loss (and better fat control) than use of diets involving higher glycemic index/load or other strategies.{{Cite journal |title=Do low glycaemic index or low glycaemic load diets help people with overweight or obesity to lose weight? |url=https://www.cochrane.org/CD005105/ENDOC_do-low-glycaemic-index-or-low-glycaemic-load-diets-help-people-overweight-or-obesity-lose-weight |access-date=2023-06-23 |website=www.cochrane.org |doi=10.1002/14651858.CD005105.pub3 |pmid=37345841 |language=en|pmc=10313499 }}

In clinical management of obesity, diets based on a low glycemic index/load appear to provide better glycemic and inflammatory control than ones based on a high glycemic index/load (and therefore could potentially be more effective in preventing obesity-related diseases).{{cite journal |vauthors=Schwingshackl L, Hoffmann G |title=Long-term effects of low glycemic index/load vs. high glycemic index/load diets on parameters of obesity and obesity-associated risks: a systematic review and meta-analysis |journal=Nutr Metab Cardiovasc Dis |volume=23 |issue=8 |pages=699–706 |year=2013 |pmid=23786819 |doi=10.1016/j.numecd.2013.04.008 |url=https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0059731/ |access-date=2017-05-30 |archive-date=2018-10-11 |archive-url=https://web.archive.org/web/20181011043251/https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0059731/ |url-status=live }} In overweight and obese children, adoption of low glycemic index/load diets may not lead to weight loss but might potentially provide other benefits.{{cite journal |vauthors=Schwingshackl L, Hobl LP, Hoffmann G |title=Effects of low glycaemic index/low glycaemic load vs. high glycaemic index/ high glycaemic load diets on overweight/obesity and associated risk factors in children and adolescents: a systematic review and meta-analysis |journal=Nutr J |volume=14 |page=87 |year=2015 |pmid=26489667 |pmc=4618749 |doi=10.1186/s12937-015-0077-1 |doi-access=free }}

Depending on quantities, the number of grams of carbohydrate in a food can have a bigger impact on blood sugar levels than the glycemic index does. Consuming less dietary energy, losing weight, and carbohydrate counting can be better for lowering the blood sugar level. Carbohydrates impact glucose levels most profoundly, and two foods with the same carbohydrate content are, in general, comparable in their effects on blood sugar. A food with a low glycemic index can have a high carbohydrate content or vice versa; this can be accounted for with the glycemic load (GL) where {{math|GL {{=}} GI% × grams of carbohydrate per serving}}.{{cn|date=January 2025}}

While the glycemic index of foods is used as a guide to the rise in blood glucose that should follow meals containing those foods, actual increases in blood glucose show considerable variability from person to person, even after consumption of identical meals. This is in part because glycemic index does not take into account other factors besides glycemic response, such as insulin response, which is measured by the insulin index and can be more appropriate in representing the effects from some food contents other than carbohydrates.{{cite web |url=http://mendosa.com/insulin_index.htm |title=David Mendosa. Insulin Index. July 13, 2003 |publisher=Mendosa.com |access-date=2012-08-01 |archive-date=2010-09-04 |archive-url=https://web.archive.org/web/20100904082116/http://www.mendosa.com/insulin_index.htm |url-status=live }} In particular, since it is based on the area under the curve of the glucose response over time from ingesting a subject food, the shape of the curve has no bearing on the corresponding GI value. The glucose response can rise to a high level and fall quickly, or rise less high but remain there for a longer time, and have the same area under the curve.{{cn|date=January 2025}}

• David Ludwig (physician)
• Diabetic diet
• Disposition index
• Glycemic efficacy
• Low glycemic index diet
• Montignac diet
• Overall nutritional quality index
• Retrogradation (starch)

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• {{cite web |author1=Human Nutrition Unit |author2=School of Molecular Bioscience |title=Glycemic Index |work=International GI database |publisher=University of Sydney |url=http://www.glycemicindex.com/foodSearch.php |ref={{harvid|Glycemic Index}}}} – Searchable database of over 2600 foods with their glycemic index and load values.
• [http://www.the-gi-diet.org/lowgifoods/ List of low GI foods]
• [https://web.archive.org/web/20060623033820/http://www.menialtools.com/GI_calculator.php Glycemic Index and Glycemic Load calculator] Total values for any combinations of foods and any number of servings are computed according to [http://www.fao.org/docrep/w8079e/w8079e0a.htm FAO/WHO specifications]).
• [https://www.diabetes.org.uk/guide-to-diabetes/enjoy-food/carbohydrates-and-diabetes/glycaemic-index-and-diabetes Diabetes UK: Glycaemic Index and Diabetes]

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Category:Diabetes

Category:Endocrinology

Category:Nutritional physiology