Glycemic index and grains

Glycemic index is very important for diabetics in managing blood sugar, or even those who have been told they are at risk for developing diabetes. Wheat, given its high use for many consumer products,has been and is the subject of many researches and studies in relation to its glycemic index. The glycemic index of a product made with wheat is related to, among other things:
the composition of the sugars of its starch
the degree of refinement of the flour used
the method of preparing the dough

Composition of wheat starch sugars
Wheat starch is composed of two sugars amylose and amylopctin. Amylose is more prevalent in quantity than amylopectin and is rapidly hydrolyzed by digestive enzymes resulting, therefore, more responsible for the “glycemic peak”. T. monococcum wheat (einkorn) is an exception because the amylose content (23.3-28.6% of the total starch) (Hidalgo et al .. 2014) is lower than durum wheat (30% ) and soft wheat (35-43
Degree of refinement of the flour
Wholemeal flour has a lower glycemic index than refined flour.
A large study examining almost 43000 people for up to 12 years found that a diet high in whole grains was inversely associated with type 2 diabetes risk [3].
Epidemiological studies have consistently shown a beneficial effect of fiber, especially wheat fiber, in reducing the risk of diabetes (1–2) and cardiovascular disease (3,4), and a recent report indicated that total dietary fiber intake was associated with reduced CHD risk factors in young people (5). Fung TT, Hu FB, Pereira MA, et al. Whole-grain intake and the risk of type 2 diabetes: a prospective study in men. American Journal of Clinical Nutrition. 2002;76(3):535–540. [PubMed] [Google Scholar]

Dough: Sourdough fermentation, the glycemic index (GI) and the glycemic load (GL).
The glycemic index (GI) is the number from 0 to 100 assigned to a food (pure glucose has been arbitrarily given the value of 100) which is indicative of the relative rise in blood glucose levels found 2h after the food has been consumed. The GI of a specific food depends primarily on the quantity and type of carbohydrate it contains, but it is also affected by numerous other factors including the amount of organic acids.
The glycemic load (GL) is a value indicating how quickly a given food portion elevates blood glucose levels. It takes into account both the amount of carbohydrates in the serving and how quickly it raises blood glucose levels (GL = GI × carbohydrate/100). A GL of 0–10 = low GL; 11–19 = medium GL; 20 and over = high GL). Sourdough fermentation of wheat flour dough significantly lowers the GI of bread by reducing the rate of starch digestion, mostly through the formation of organic acids that delay the absorption of starch [6]. Starch is absorbed more slowly in the presence of lactic acid due to the inhibition of amylolytic enzymes, and its bioavailability is reduced due to the interaction between starch and gluten [7]. Acetic acid delays the gastric empting rate [8]. The Mediterranean way: why elderly people should eat wholewheat sourdough bread—a little known component of the Mediterranean diet and healthy food for elderly adults. Antonio Capurso, Cristiano Capurso. 13 november 2019 springer

References
1 – Liu S, Manson JE, Stampfer MJ, Hu FB, Giovannucci E, Colditz GA, Hennekens CH, Willett WC: A prospective study of whole-grain intake and risk of type 2 diabetes mellitus in US women. Am J Public Health 90: 1409–1415, 2000 PubMedWeb of ScienceGoogle Scholar

2 – Salmeron J, Ascherio A, Rimm EB, Colditz GA, Spiegelman D, Jenkins DJ, Stampfer MJ, Wing AL, Willett WC: Dietary fiber, glycemic load, and risk of NIDDM in men. Diabetes Care 20:545–550, 1997.  Abstract/FREE Full TextGoogle Scholar

3 – Liu S, Stampfer MJ, Hu FB, Giovannucci E, Rimm E, Manson JE, Hennekens CH, Willett WC: Whole-grain consumption and risk of coronary heart disease: results from the Nurses’ Health Study. Am J Clin Nutr 70:412–419, 1999. Abstract/FREE Full TextGoogle Scholar

4 – Wolk A, Manson JE, Stampfer MJ, Colditz GA, Hu FB, Speizer FE, Hennekens CH, Willett WC: Long-term intake of dietary fiber and decreased risk of coronary heart disease among women. JAMA 281:1998–2004, 1999
CrossRefPubMedWeb of ScienceGoogle Scholar
5 – Ludwig DS, Pereira MA, Kroenke CH, Hilner JE, Van Horn L, Slattery ML, Jacobs DR Jr: Dietary fiber, weight gain, and cardiovascular disease risk factors in young adults. JAMA 282:1539–1546, 1999.  CrossRefPubMedWeb of ScienceGoogle Scholar
6 – Poutanen K, Flander L, Katina K (2009) Sourdough and cereal fermentation in a nutritional perspective. Food Microbiol 26:693–699
7 – Liljeberg H, Björck I (1998) Delayed gastric emptying rate may explain improved glycaemia in healthy subjects to a starchy meal with added vinegar. Eur J Clin Nutr 52:368–371
8 – Atkinson FS, Foster-Powell K, Brand-Miller JC (2008) International tables of glycemic index and glycemic load values: 2008. Diabetes Care 31:2281–2283

Note
“The glycemic index [GI] a system that ranks foods on a scale from 1 to 100 based on their effect on blood-sugar levels.”
The purpose of this scale is so that sensitive individuals can judge the impact a particular food will have on their blood sugar, and either eat or avoid it accordingly. This is very important for diabetics in managing blood sugar, or even those who have been told they are at risk for developing diabetes.
Now, that rank is from 1 to 100, but that means nothing without context.
• High GI foods are ranked at 70 or greater — like potatoes
• Medium GI foods are ranked at 56 to 69 — like sweet potatoes and corn; sweeter fruits like pineapple and apricots; and millet
• Low GI foods are ranked at 55 or lower — like carrots and other moderately sweet vegetables, most other fruits, most nuts/seeds; beans; dairy; and most grains
• Very Low GI foods are ranked below any of these because they have no impact on blood sugar or no established GI value — like non-starchy vegetables; spices; herbs; and meats and seafood
By the way, this information comes from The World’s Healthiest Foods.
The high GI foods cause a sudden and extreme spike in blood sugar levels, while medium/low GI foods produce a more gradual increase.

Kewords: glycemic index, glycemic load, einkorn, monococcum wheat, Wholemeal flour