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Eat Beans to Improve Your Health: Part 4

The following article is the last in a series of four papers on the health and nutritional value of dry beans. The papers, edited and researched by Maurice R. Bennink, Ph.D., and Elizabeth A. Rondini, MS, RD, of Michigan State University, were released earlier this year. To read the series in its entirety, visit www.michiganbean.org.

Introduction. In the first three parts of this series we reviewed the relationship between bean intake to cancer, obesity, and cardiovascular disease. The potential adverse consequences of hyperglycemia and hyperinsulinemia to regulation of food consumption as well as cancer risk were also discussed. In this review, evidence linking low glycemic index diets to improvements in diabetes management as well as diabetes risk will be addressed. As in previous sections, few studies have looked directly at bean consumption. However, because beans have a low glycemic index relative to other carbohydrate starches they will be discussed in this context.

Low glycemic index diets for diabetes management. It has long been recognized that components present in food, particularly soluble dietary fiber and the nature of the starch can influence the rate by which glucose is absorbed from the small intestine (reviewed in 1 & 2). In the mid-1970s, research began to focus on manipulating dietary fiber and carbohydrates to help individuals with diabetes manage their blood glucose. In several clinical trials, it was shown that incorporation of very high amounts of fiber in the diet improved parameters associated with hyperglycemia and even lowered exogenous insulin requirements in some diabetics (3-8). However, it is very difficult for most individuals to consume such a high level of dietary fiber on a regular basis. Around the same time, several groups began to focus their attention on glycemic and insulin responses to different carbohydrate sources (9-13). Jenkins et al. later introduced the concept of glycemic index to characterize these differences (11). The glycemic index, defined in a previous section, is the ability of different sources of carbohydrates to increase blood glucose over a period of time compared to either glucose or white bread. Legumes in particular were found to produce relatively low glycemic responses in both healthy individuals (11) and in diabetics (12-13).

Eating low glycemic index diets may be one mechanism to minimize the normal rise in blood glucose that occurs following meals and therefore aid in the management of diabetes. Diabetes is a chronic condition associated with many metabolic abnormalities including elevated blood glucose and triglycerides. Individuals are instructed to lower blood glucose levels to help reduce the potential for complications associated with the disease. Many of these complications, including vascular disease and death, are related to the long-term effects of hyperglycemia (14). Several feeding studies have shown improvements in glycemic control in both type 1 and type 2 diabetics when low compared to high glycemic index diets are consumed (summarized in 15-16; 17-26). In a recent study with type 1 diabetic children, dietary advice about how to consume a low glycemic index diet was reported to be more beneficial and less of a burden than utilization of the traditional carbohydrate exchange diet (18). In this study, improvements in glycosylated HbA1C and a reduced number of excessive hyperglycemic episodes were reported in children instructed to consume low glycemic index foods. Glycosylated proteins reflect blood glucose levels over long periods of time. Chronic elevations of blood glucose increase the amount of glycosylated blood proteins in blood and vice versa. In feeding studies with type 2 diabetics (adult-onset), lower fasting blood glucose (17), glycosylated proteins (17, 20-22, 25), insulin secretion (17, 22), and lipoproteins (14, 21, 22, 25) have been reported by lowering dietary glycemic index. Although still relatively few in number, these studies provide evidence that simply substituting low glycemic index carbohydrates such as beans for more processed starches can modestly improve glycemic control in diabetics. We acknowledge that some health scientists prefer to not use the concept of glycemic index, but instead emphasize high fiber foods with low caloric density. Regardless of the approach, beans are a highly desirable food since they have a low glycemic index and at the same time they are a high fiber, low caloric dense food.

High glycemic index diets and risk of type 2 diabetes. Consumption of complex carbohydrates and increasing soluble dietary fiber intake was originally advocated for individuals with diabetes and hyperlipidemia. However, two large epidemiological studies have now indicated that long-term consumption of high glycemic index, starchy foods may also increase the risk of developing type 2 diabetes (27-28). In these studies, individuals were followed for a period of time (6 years) and dietary comparisons were made between individuals diagnosed with diabetes and non-diabetics. In both studies, the researchers found a 37% increase in diabetes in individuals with the highest glycemic index intake compared to those having the lowest glycemic index intake after adjustment for known risk factors and cereal fiber. Foods most associated with diabetes risk included French fries, carbonated beverages, white bread, and white rice (27-28). The exact reason why consumption of high glycemic index foods leads to an increased risk for type 2 diabetes is not known but may be due to an increase in insulin demand (2, 15-16, 29). High glycemic index foods are known to cause rapid elevations in blood glucose and insulin following a meal. Chronic consumption of high glycemic index diets may in turn lead to down-regulation or desensitization of receptors for insulin, eventually contributing to insulin resistance (2). The body initially adjusts to higher circulating glucose by increasing insulin secretion from the pancreas. However, in susceptible individuals over time insulin resistance combined with exhaustion of insulin producing cells will eventually lead to type 2 diabetes (15-16). Current research (30-31) also suggests that hyperglycemia and hyperinsulinemia stimulate fat cells and possibly cells that line blood vessels (endothelial cells) to secrete pro-inflammatory cytokines called tumor necrosis factor alpha (TNF-a) and interleukin-6 (IL-6). These cytokines promote insulin resistance and other clinical and biochemical symptoms associated with type 2 diabetes. In addition, these cytokines are predictive of risk for cardiovascular disease.

In conclusion, eating a diet rich in low glycemic index foods may help prevent development of diabetes. For diabetics and individuals with impaired glucose tolerance, a low glycemic index diet is important to help control hyperglycemia and hyperinsulinemia and reduce complications of diabetes such as atherosclerosis and kidney failure.

References:

1. Jenkins DJA, Taylor RH, and Wolever TMS. (1982) The Diabetic Diet, Dietary Carbohydrate and Differences in Digestibility. Diabetologia 23 (6), 477-484

2. Jenkins DJA, Axelsen M, Kendall CWC, Augustin LSA, Vuksan V, and Smith U. (2000) Dietary fibre, lente carbohydrates and the insulin-resistant diseases. British Journal of Nutrition 83, S157-S163

3. Kiehm TG, Anderson JW, and Ward K. (1976) Beneficial Effects of a High Carbohydrate, High Fiber Diet on Hyperglycemic Diabetic Men. American Journal of Clinical Nutrition 29, 895-99

4. Anderson JW. (1978) Improved Glucose and Lipid-Metabolism in Diabetic Men Treated with High-Carbohydrate, High-Fiber Diets. Clinical Research 26(3), A526-A526

5. Anderson JW and Ward K. (1979) High-Carbohydrate, High-Fiber Diets for Insulin-Treated Men with Diabetes-Mellitus. American Journal of Clinical Nutrition 32 (11), 2312-2321

6. Anderson JW and Ratliff P. (1987) High-Carbohydrate, High-Fiber Diets Decrease Insulin Requirements of Type-I Diabetic Individuals. Clinical Research 35 (6), A898-A898

7. Anderson JW, Zeigler JA, Deakins DA, Floore TL, Dillon DW, Wood CL, Oeltgen PR, and Whitley RJ. (1991) Metabolic Effects of High-Carbohydrate, High-Fiber Diets for Insulin-Dependent Diabetic Individuals. American Journal of Clinical Nutrition 54 (5), 936-943

8. Simpson HCR, Lousley S, Geekie M, Simpson RW, Carter RD, Hockaday TDR, and Mann JI. (1981) A High-Carbohydrate Leguminous Fiber Diet Improves All Aspects of Diabetic Control. Lancet 1 (8210), 1-4

9. Crapo PA, Kolterman OG, Waldeck N, Reaven GM, and Olefsky JM. (1980) Postprandial hormonal responses to different types of complex carbohydrate in individuals with impaired glucose tolerance. American Journal of Clinical Nutrition 33, 1723-28

10. Coulston A, Greenfield M, Kraemer F, Tobey T, and Reaven G. (1980) Effect of Source of Dietary Carbohydrate on Plasma-Glucose and Insulin Responses to Test Meals in Normal Subjects. American Journal of Clinical Nutrition 33 (6), 1279-1282

11. Jenkins DJA, Wolever TMS, Taylor RH, Barker H, Fielden H, Baldwin JM, Bowling AC, Newman HC, Jenkins AL, and Goff DV. (1981) Glycemic index of foods: a physiological basis for carbohydrate exchange. American Journal of Clinical Nutrition 34, 362-66

12. Jenkins DJA, Wolever TMS, Jenkins AL, Thorne MJ, Lee R, Kalmusky J, Reichert R, and Wong GS. (1983) The Glycemic Index of Foods Tested in Diabetic-Patients - a New Basis for Carbohydrate Exchange Favoring the Use of Legumes. Diabetologia 24 (4), 257-264

13. Viswanathan M, Ramachandran A, Indira P, John S, Snehalatha C, Mohan V, and Kymal PK. (1989) Responses to Legumes in NIDDM Subjects - Lower Plasma-Glucose and Higher Insulin Levels. Nutrition Reports International 40 (4), 803-812

14. Stratton IM, Adler AI, Neil HAW, Matthews DR, Manley SE, Cull CA, Hadden D, Turner RC, and Holman RR. (2000) Association of glycaemia with macrovascular and microvascular complications of type 2 diabetes (UKPDS 35): prospective observational study. British Medical Journal 321 (7258), 405-412

15. Ludwig DDS. (2002) The glycemic index - Physiological mechanisms relating to obesity, diabetes, and cardiovascular disease. Journal of the American Medical Association 287 (18), 2414-2423

16. Augustin LS, Franceschi S, Jenkins DJA, Kendall CWC, and La Vecchia C. (2002) Glycemic index in chronic disease: a review. European Journal of Clinical Nutrition 56 (11), 1049-1071

17. Jenkins DJA, Wolever TMS, Buckley G, Lam KY, Giudici S, Kalmusky J, Jenkins AL, Patten RL, Bird J, Wong GS, and Josse RG. (1988) Low-Glycemic-Index Starchy Foods in the Diabetic Diet. American Journal of Clinical Nutrition 48 (2), 248-254

18. Gilbertson HR, Brand-Miller JC, Thorburn AW, Evans S, Chondros P, and Werther GA. (2001) The effect of flexible low glycemic index dietary advice versus measured carbohydrate exchange diets on glycemic control in children with type 1 diabetes. Diabetes Care 24 (7), 1137-1143

19. Buyken AE, Toeller M, Heitkamp G, Karamanos B, Rottiers R, Muggeo M, and Fuller JH. (2001) Glycemic index in the diet of European outpatients with type 1 diabetes: relations to glycated hemoglobin and serum lipids. American Journal of Clinical Nutrition 73 (3), 574-581

20. Brand JC, Colagiuri S, Crossman S, Allen A, Roberts DCK, and Truswell AS. (1991) Low-Glycemic Index Foods Improve Long-Term Glycemic Control in NIDDM. Diabetes Care 14 (2), 95-101

21. Wolever TMS, Jenkins DJA, Vuksan V, Jenkins AL, Wong GS, and Josse RG. (1992) Beneficial Effect of Low-Glycemic Index Diet in Overweight NIDDM Subjects. Diabetes Care 15 (4), 562-564

22. Wolever TMS, Jenkins DJA, Vuksan V, Jenkins AL, Buckley GC, Wong GS, and Josse RG. (1992) Beneficial effect of a low glycemic index diet in type 2 diabetes. Diabetes Medicine 9, 451-58

23. Fontvieille AM, Rizkalla SW, Penfornis A, Acosta M, Bornet FRJ, and Slama G. (1992) The Use of Low Glycemic Index Foods Improves Metabolic Control of Diabetic-Patients over 5 Weeks. Diabetic Medicine 9 (5), 444-450

24. Miller JCB. (1994) Importance of Glycemic Index in Diabetes. American Journal of Clinical Nutrition 59 (3), S747-S752

25. Jarvi AE, Karlstrom BE, Granfeldt YE, Bjorck IE, Asp NGL, and Vessby BOH. (1999) Improved glycemic control and lipid profile and normalized fibrinolytic activity on a low-glycemic index diet in type 2 diabetic patients. Diabetes Care 22 (1), 10-18

26. Giacco R, Parillo M, Rivellese AA, Lasorella G, Giacco A, D'Episcopo L, and Riccardi G. (2000) Long-term dietary treatment with increased amounts at fiber-rich low-glycemic index natural foods improves blood glucose control and reduces the number of hypoglycemic events in type 1 diabetic patients. Diabetes Care 23 (10), 1461-1466

27. Salmeron J, Ascherio A, Rimm EB, Colditz GA, Spiegelman D, Jenkins DJ, Stampfer MJ, Wing AL, and Willett WC. (1997) Dietary fiber, glycemic load, and risk of NIDDM in men. Diabetes Care 20 (4), 545-550

28. Salmeron J, Manson JE, Stampfer MJ, Colditz GA, Wing AL, and Willett WC. (1997) Dietary fiber, glycemic load, and risk of non-insulin-dependent diabetes mellitus in women. Journal of the American Medical Association 277 (6), 472-477

29. Jenkins DJA, Wolever TMS, Collier GR, Ocana A, Rao AV, Buckley G, Lam Y, Mayer A, and Thompson LU. (1987) Metabolic effects of a low-glycemic index diet. American Journal of Clinical Nutrition 46, 968-75

30. Esposito K, Nappo F, Marfella R, Giugliano G, Giugliano F, Ciotola M, Quagliaro L, Ceriello A, and Giugliano D. (2002) Inflammatory cytokine concentrations are acutely increased by hyperglycemia in humans - Role of oxidative stress. Circulation 106 (16), 2067-2072

31. Soop M, Duxbury H, Agwunobi AO, Gibson JM, Hopkins SJ, Childs C, Cooper RG, Maycock P, Little RA, and Carlson GL. (2002) Euglycemic hyperinsulinemia augments the cytokine and endocrine responses to endotoxin in humans. American Journal of Physiology-Endocrinology and Metabolism 282 (6): E1276-E1285.