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Glycemic Index and Glycemic Load

Glycemic Index and Glycemic Load

  • Not all carbohydrates are created equal! There are good carbohydrates (carbs), not so good carbs, and bad carbs. It also matters how much carb you take at a time, or a day. A high glycemic load precipitates and aggravates glucose intolerance, metabolic syndrome, and diabetes, particularly in India.1
  • The glycemic index is a scientific measure of how much a standard quantity of food raises blood glucose levels compared with a standard quantity of glucose or white bread. The glycemic index is obtained from published food tables.
  • The glycemic index is an extension of the fiber hypothesis and largely depends on the  rate of digestion and speed of absorption of carbohydrate, but physical form is also important.2, 3
  • Carbohydrate classified by glycemic index, in contrast to its traditional classification as either simple or complex, is a better coronary artery disease (CAD) predictor in epidemiological studies.4
  • Foods with high levels of soluble fiber such as rye, barley, and oats are digested at a lower rate and have lower glycemic index. Foods containing the same amount of carbohydrate (carbohydrate exchange) may have up to a 5-fold difference in glycemic impact, depending on the differences in the digestion and absorption.5
  • The hierarchy of the glycemic index begins with beans, lentils, rice, spaghetti, potatoes, white bread (with refined flour), and refined grain cereals.6  A high glycemic index indicates a lower quality of carbohydrate associated with low HDL levels and low rates of satiety.5
  • The glycemic index above 70 is considered high and below 55 is low while an index between 56 and 69 is considered medium.
  • Fruits, non-starchy vegetables, parboiled rice, and legumes have a low glycemic index.7 The glycemic index of potato is 102%, white bread is 100%, whereas apple is 55%, and broccoli is 13%.
  • Glycemia observed after consuming dried peas is only one-third that of an equivalent amount of potatoes. Since peas are also high in fiber, its consumption needs to be encouraged, especially in patients with diabetes and metabolic syndrome.5
  •  Prolonged cooking of vegetables, as is commonly practiced in India, virtually destroys every nutrient before it is consumed as well as increases the glycemic index.

Glycemic Load

  • The amount of carbohydrate in a food or overall diet varies considerably. The glycemic load is the product of  the glycemic index of a food item and the available carbohydrate content of that item. A high glycemic load raises the blood levels of triglycerides, blood sugar, and insulin while decreasing HDL, all of which contribute to increased risk of heart disease.
  • Carrot has a high glycemic index but a low glycemic load. The glycemic load is the product of the glycemic value of the food and its carbohydrate content (per serving) divided by 100. Each unit of dietary glycemic load represents the equivalent of 1g carbohydrate from glucose.
  • The overall daily dietary glycemic load is calculated by adding the glycemic loads of all different foods consumed in a given day. Accordingly, the glycemic load can be decreased by reducing the amount of carbohydrate intake and/or by consuming foods with low glycemic index.8
  • In addition to the quality and quantity of carbohydrates consumed, the glycemic load also represents diet-induced insulin demand.9, 10
  • Both glycemic index and glycemic load are inversely associated with HDL and directly associated with triglycerides.11
  • In the Nurses Health Study, high glycemic load was associated with double the risk of CAD among obese women.12
  • Asian Indians consume large quantities of carbohydrates in the form of rice and bread which predisposes them for atherogenic dyslipidemia. Carbohydrate source, nature, and amount have profound influence on post-prandial glycemia (blood sugar after a meal) , and  post-prandial  lipemia (triglycerides after a meal) which in turn are  directly associated with risk of CAD in patients with diabetes.5
  • The time has come to shift the diet-heart paradigm away from restricted fat intake towards reduced glycemic load.13

Glycemic load and diabetes

  • A high glycemic load diet increases insulin demand and may lead to pancreatic beta cell exhaustion in the long run leading to diabetes.14 Fructose from high fructose syrup also has similar effects.15
  • On the other hand, a diet high in whole grains, fruits and vegetables and low in sodium and saturated fat can prevent and control hypertension, diabetes and cardiovascular diseases (CVD).
  • Glycemic load promotes diabetes, especially in those with insulin resistance.4, 16-20  This is particularly true for refined carbohydrates, sweets, white bread, and potatoes. Thus, high glycemic load may be considered a risk factor of equal importance as high saturated fat diet in precipitating diabetes.
  • A low glycemic load can reduce insulin secretion in patients with type 2 diabetes, decrease insulin requirements in type 1 diabetes, and improve blood sugar control in both types of diabetes.
  • The incremental benefit from low glycemic load is similar to that offered by medicines that also target postprandial hyperglycemia (alpha-glycosidase inhibitors such as precose, glycet).5
  • The benefit of low glycemic load on the development of diabetes is similar to monounsaturated fat, polyunsaturated fat, whole grains, fiber, fruits, and vegetables.
  • A diet with high glycemic load, resulting in high triglycerides and low HDL levels is a major overlooked factor for atherogenic dyslipidemia, metabolic syndrome and diabetes  among asian indians.21
  • There appears to be a threshold for carbohydrate consumption with intake  >280 g/d often resulting in atherogenic dyslipidemia.22
  • Replacing high glycemic with low glycemic index  foods and reducing the glycemic load can reduce the risk of diabetes and CVD.20
  • Recent popularity of low carbohydrate diets may have helped to generate new awareness of the distinction between refined and complex carbohydrate foods. The former generally refers to sugar-dense foods whereas the latter is found in fruits, vegetables and whole grains, the very foods that are advocated to help control weight and reduce risk for cardiovascular and other chronic diseases.23

Sources

1. Enas EA. Indian diet and cardiovascular disease: An update. In: Chatterjee SS, ed. Update in Cardiology Hyderabad: Cardiology Society of India.; 2007.

2. Jenkins DJ, Wolever TM, Taylor RH, et al. Glycemic index of foods: a physiological basis for carbohydrate exchange. Am J Clin Nutr. 1981;34(3):362-366.

3. Jenkins  DJ, Kendall CW, Augustin LS, et al. Glycemic index: overview of implications in health and disease. Am J Clin Nutr. 2002;76(1):266S-273S.

4. Liu S, Willett WC, Stampfer MJ, et al. A prospective study of dietary glycemic load, carbohydrate intake, and risk of coronary heart disease in US women. Am J Clin Nutr. 2000;71(6):1455-1461.

5. Enas EA, Senthilkumar A, Chennikkara H, Bjurlin MA. Prudent diet and preventive nutrition from pediatrics to geriatrics: current knowledge and practical recommendations. Indian heart journal. Jul-Aug 2003;55(4):310-338.

6. Bornet FR, Costagliola D, Rizkalla SW, et al. Insulinemic and glycemic indexes of six starch-rich foods taken alone and in a mixed meal by type 2 diabetics. Am J Clin Nutr. Mar 1987;45(3):588-595.

7. Ludwig  DS. The glycemic index: physiological mechanisms relating to obesity, diabetes, and cardiovascular disease. Jama. 2002;287(18):2414-2423.

8. Wolever TM, Mehling C. Long-term effect of varying the source or amount of dietary carbohydrate on postprandial plasma glucose, insulin, triacylglycerol, and free fatty acid concentrations in subjects with impaired glucose tolerance. Am J Clin Nutr. 2003;77(3):612-621.

9. Wolever TM, Jenkins DJ, Jenkins AL, Josse RG. The glycemic index: methodology and clinical implications. Am J Clin Nutr. Nov 1991;54(5):846-854.

10. Stevens J, Ahn K, Juhaeri, Houston D, Steffan L, Couper D. Dietary fiber intake and glycemic index and incidence of diabetes in African-American and white adults: the ARIC study. Diabetes Care. 2002;25(10):1715-1721.

11. Beulens JW, de Bruijne LM, Stolk RP, et al. High dietary glycemic load and glycemic index increase risk of cardiovascular disease among middle-aged women: a population-based follow-up study. J Am Coll Cardiol. Jul 3 2007;50(1):14-21.

12. Flight I, Clifton P. Cereal grains and legumes in the prevention of coronary heart disease and stroke: a review of the literature. Eur J Clin Nutr. Oct 2006;60(10):1145-1159.

13. Hu FB. Diet and cardiovascular disease prevention the need for a paradigm shift. J Am Coll Cardiol. Jul 3 2007;50(1):22-24.

14. Hu FB, Willett WC. Optimal diets for prevention of coronary heart disease. Jama. Nov 27 2002;288(20):2569-2578.

15. Stanhope KL, Havel PJ. Fructose consumption: recent results and their potential implications. Ann N Y Acad Sci. Mar 2010;1190:15-24.

16. Jeppesen J, Schaaf P, Jones C, Zhou MY, Chen YD, Reaven GM. Effects of low-fat, high-carbohydrate diets on risk factors for ischemic heart disease in postmenopausal women. Am J Clin Nutr. Apr 1997;65(4):1027-1033.

17. Mann J. Diet and risk of coronary heart disease and type 2 diabetes. Lancet. 2002;360(9335):783.

18. Salmeron J, Ascherio A, Rimm EB, et al. Dietary fiber, glycemic load, and risk of NIDDM in men. Diabetes Care. 1997;20(4):545-550.

19. Salmeron J, Manson JE, Stampfer MJ, Colditz GA, Wing AL, Willett WC. Dietary fiber, glycemic load, and risk of non-insulin-dependent diabetes mellitus in women. Jama. Feb 12 1997;277(6):472-477.

20. Willett W, Manson J, Liu S. Glycemic index, glycemic load, and risk of type 2 diabetes. Am J Clin Nutr. 2002;76(1):274S-280S.

21. Abbasi F, McLaughlin T, Lamendola C, et al. High carbohydrate diets, triglyceride-rich lipoproteins, and coronary heart disease risk. Am J Cardiol. 2000;85(1):45-48.

22. Yagalla MV, Hoerr SL, Song WO, Enas E, Garg A. Relationship of diet, abdominal obesity, and physical activity to plasma lipoprotein levels in Asian Indian physicians residing in the United States. J Am Diet Assoc. 1996;96(3):257-261.

23. Lichtenstein AH, Appel LJ, Brands M, et al. Diet and lifestyle recommendations revision 2006: a scientific statement from the American Heart Association Nutrition Committee. Circulation. Jul 4 2006;114(1):82-96.

 

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