Glycemic Load - by Maelán Fontes and Pedro Bastos
Greetings,
I took the course Dr. Cordain gave to optometrists in Calgary, AB in 2009 on nutrition and quite enjoyed it, and found the discussion about glycemic load of special interest. He said that dairy products and fructose especially had a high glycemic load rating yet in the chart produced by Dr. Jenny Brand-Miller of the U. of Sydney, in Australia, her chart shows the opposite for those two items. Where does Dr. Cordain get his information, and where do I go from here? Thanks.
Dr. H. T. Warner
Vernon, BC Canada
Dear Dr. Warner,
Thanks for following our work. I think there might be some kind of misinterpretation of Dr. Cordain’s slides or words, since his slides do not show that dairy products and fructose have high glycemic loads, and his scientific work demonstrates otherwise1-3. While I am sure you are familiar with the glycemic index (GI) and glycemic load (GL) concepts, however, I’ll briefly explain them.
The glycemic index (GI) was created in 1981 and it is as measure of how quickly food containing 25 or 50 grams of carbohydrates raise blood sugar levels4. Because the carbohydrate content of foods varies enormously from food to food and from serving to serving, Harvard researchers created the glycemic load (GL), which takes into account the GI and the amount of carbohydrates in a given serving of a food4 which provides a more useful measure1. To calculate the GL, we simply multiply the GI by the amount of carbohydrates in a given portion size and divide by 100 (GL=GI x amount of carbohydrate in a given serving/100)4.
It has been established that in most carbohydrate-containing foods blood insulin response is closely linked to the food’s GL2.
As such, a high GL food (such as white bread, which is many time used as a reference, because of its very high GI/GL4), by rapidly increasing blood sugar levels, stimulates the pancreas to produce more insulin than a low GL food (such as an apple1, 4). This is why people who consume these foods (sugar containing foods, potatoes and many grain based products1) present5 higher 24-hour plasma insulin levels than individuals who follow a low GL diet, such as The Paleo Diet. The Paleo Diet’s main sources of carbohydrates are fruits, vegetables and nuts, which present a much lower GL than most cereal grains (even whole grains)1,4.
As I’m sure you are aware, a chronic state of hyperinsulinemia may lead to insulin resistance (IR)6-9 (the primary metabolic defect underlying The Metabolic Syndrome, which greatly increases the risk for cardiovascular disease and mortality1). Insulin resistance can also be a driving force in obesity10-12 and can cause a hormonal cascade that ultimately results in certain epithelial cell cancers, Polycystic Ovarian Syndrome, Male Vertex Balding, Acne and Juvenile Myopia, among other diseases1, 13.
Regarding the GL of fructose, if you review at Dr. Cordain’s scientific paper1 entitled "Hyperinsulinemic diseases of civilization: more than just Syndrome X," you will see in Table 1 that the GL of fructose (per 100 g portion) is low (22.9). Nevertheless, despite having a low GL, fructose may lead to IR through different mechanisms (e.g. increasing triglycerides and uric acid)1, 14, and play an important role in all the diseases associated with IR1, 14.
Concerning the GL of Milk, if you review his papers (Hoyt G, Hickey MS and Cordain L. "Dissociation of the glycaemic and insulinaemic responses to whole and skimmed milk." British Journal of Nutrition 2005; 93: 175–177, and Cordain et al. "Origins and evolution of the Western diet: health implications for the 21st century." Am J Clin Nutr 2005;81:341–54), you will see that whole milk and skim milk both have a low GL, but unexpectedly, they elicit a very high insulin response similar to that of glucose2.
This is explained by the presence of whey in milk, since whey proteins induces high insulin production, perhaps by increasing GLP-1 and GIP2, 13.
Taken together, the common use of high GL foods, fructose (including high-fructose corn syrup), and dairy products in the Western diet1 may contribute to the high prevalence of Western diseases named above. These types of foods were rarely, if ever, consumed by our hunter-gatherers ancestors3.
References:
1. Cordain L, Eades MR and Eades MD. Hyperinsulinemic diseases of civilization: more than just Syndrome X. Comparative Biochemistry and Physiology Part A 136 (2003) 95–112.
2. Hoyt G, Hickey MS and Cordain L. Dissociation of the glycaemic and insulinaemic responses to whole and skimmed milk. British Journal of Nutrition (2005), 93, 175–177.
3. Cordain et al. Origins and evolution of the Western diet: health implications for the 21st century. Am J Clin Nutr 2005;81:341–54.
4. Foster-Powell K, Holt SHA, and Brand-Miller. JC. International table of glycemic index and glycemic load values: 2002. Am J Clin Nutr 2002;76:5–56.
5. Kiens B, Richter EA. Types of carbohydrate in an ordinary diet affect insulin action and muscle substrates in humans. Am J Clin Nutr. 1996 Jan;63(1):47-53.
6. Rizza RA, Mandarino LJ, Genest J, Baker BA, Gerich JE. Production of insulin resistance by hyperinsulinaemia in man. Diabetologia. 1985 Feb;28(2):70-5.
7. Treadway JL, Whittaker J, Pessin JE. Regulation of the insulin receptor kinase by hyperinsulinism. J Biol Chem 1989;264:15136–15143.
8. DelPrato S, Leonetti F, Simonson DC, et al. Effect of sustained physiologic hyperinsulinaemia and hyperglycaemia on insulin secretion and insulin sensitivity in man. Diabetologia 1994;37:1025-1035.
9. Flores-Riveros JR, McLenithan JC, Ezaki O, Lane MD. Insulin down-regulates expression of the insulin-responsive glucose transporter (GLUT4) gene: effects on transcription and mRNA turnover. Proc Natl Acad Sci 1993;90:512–6.
10. Thomas DE, Elliott EJ, Baur L. Low glycaemic index or low glycaemic load diets for overweight and obesity. Cochrane Database Syst Rev. 2007 Jul 18;(3):CD005105.
11. de Rougemont A, Normand S, Nazare JA, Skilton MR, Sothier M, Vinoy S, Laville M. Beneficial effects of a 5-week low-glycaemic index regimen on weight control and cardiovascular risk factors in overweight non-diabetic subjects. Br J Nutr. 2007 Dec;98(6):1288-98. Epub 2007 Jul 9.
12. Nishino N, Tamori Y, Kasuga M. Insulin efficiently stores triglycerides in adipocytes by inhibiting lipolysis and repressing PGC-1alpha induction. Kobe J Med Sci. 2007;53(3):99-106.
13. Melnik BC. Permanent impairment of insulin resistance from pregnancy to adulthood: The primary basic risk factor of chronic Western diseases. Medical Hypotheses 73 (2009) 670–681.
14. Segal MS, Gollub E and Johnson RJ. Is the fructose index more relevant with regards to cardiovascular disease than the glycemic index? Eur J Nutr (2007) 46:406–417.
