Title: The importance of glycaemic control in the management of diabetes

Key words: diabetes, metabolic, glycaemic, pancreatic, islet cell, type 1, type 2, obesity, glucose, lipid, protein, microvascular, macrovascular, neurological, cardiovascular, lifestyle, glucose tolerance, visceral adiposity, weight control, hyperglycaemia, hypoglycaemia, dyslipidaemia, dysglycaemia, risk factors, free fatty acids, soluble fibre, insulin sensitivity, low saturated fat, diet, lipid profiles, cholesterol, triglycerides, monounsaturates, low density lipoproteins, olive oil, phytonutrient, antioxidants, sucrose, glycation,

Date: Sept 2006

Category: Specific conditions

Nutrimed Module:

Type: Article

Author: Morgan, G

 

The importance of glycaemic control in the management of diabetes

Diabetes is a metabolic disease associated with loss of normal glycaemic control, either due to pancreatic islet cell failure ( type 1 or insulin-dependent diabetes mellitus) or to peripheral insulin resistance (type 2 or non-insulin-dependent diabetes mellitus). Type 2 is now a major worldwide public health problem due to its associations with obesity which has nearly doubled in many countries over the last 10 years (WHO 1998). Though the metabolic disorder of diabetes affects both glucose, lipid and protein metabolism, diagnostically and prognostically it may be delineated by the level of its glycaemic control. A focus on this parameter remains central to its clinical management.

 

Large prospective studies have demonstrated the value of tighter glycaemic control in diabetes. These have shown a reduction in the risk of developing associated microvascular and neurological disease (Diabetes Control & Complications Trial 1993, Ohbuko 1995, UK Prospective Diabetes Study 1998), and indicated a benefit for macrovascular disease (UK Prospective Diabetes Study 1998).

 

Hyperglycaemia and diabetes have been shown to be independent risk factors for cardiovascular disease, accounting for some 65% of all deaths in diabetics (Wilson 1998, Grundy 1999), the risk for type 2 diabetes being able to be halved by early intensive dietary, lifestyle and drug treatment (Diabetes Prevention Program 1999). Early detection is imperative as only those in the top 2.5th percentile for impaired glucose tolerance carry an increased risk when followed up for 20 years (Balkau 1998)

 

Obesity, particularly visceral adiposity, is closely linked to the development of both cardiovascular disease and diabetes (Despres 2001). Though a WHO report (Chaturvedi 1995) was unable to link obesity and established diabetes with associated cardiovascular disease and overall mortality, weight reduction remains central to diabetic management as low calorie diets, regardless of their composition, have led to reductions in hyperglycaemia, insulin secretion and dyslipidaemia (Brown 1996, Heilbronn 1999, Foster 2003), reductions of 5% or more in weight loss reducing the associated cardiovascular risk factors (Franz 1994, Parillo 2004). Both excess fat, particularly as saturated or trans-fatty acids (Riccardi 2000), and carbohydrates (Garg 1994, Parillo 1996) have been linked to dysglycaemia and dyslipidaemia. Free fatty acids are known to impair insulin sensitivity and promote hyperglycaemia (Storlein 1996), low saturated fat diets being increasingly promoted in the treatment of diabetes (Mann 2002). The evidence on high carbohydrate diets is somewhat equivocal. Most studies have shown an aggravation of glycaemic control (Garg 1994, Parillo 1996, Riccardi 2000), whilst some studies have shown none or a beneficial effect (Komiyama 2002, Yang 2003). Such research variability may reflect differences in study design and food composition.

 

Specifically, carbohydrates with a low-glycaemic index are characterized by a high-fibre content (Jenkins 2002). Both have independently improved glycaemic control and lipid profiles (Giacco 2000, Chandalia 2000, Brand-Miller 2003). A recent 8 year prospective trial (Schulze 2004) has shown both to be inversely correlated with the development of type 2 diabetes. Soluble fibre, in particular, e.g. in foods such as pulses, has been linked to an improved metabolic profile, tighter weight control, and an improvement in the cardiovascular parameters associated with diabetes (Rizkalla 2002). The deleterious effects of high carbohydrate diets have been shown to be negated by increasing their low-glycaemic index and high-fibre components (Riccardi 2000).

 

The beneficial effects of low-glycaemic index/high-fibre diets need to be qualified. In a meta-analysis of 14 studies, Brand-Miller (Brand-Miller 2003) noted that the mean reduction in HbA1c levels between high- and low-glycaemic index diets was only 7.4%. Changes in fasting plasma glucose, total cholesterol, triglycerides and very low-density lipoproteins were of a similar order between high and low-fibre diets (Chandalia 2000). The direction of these changes is concordant with that of another dietary intervention, namely that of increasing the relative proportion of fatty acids as monounsaturates in the diet (Garg 1998, Vessby 2001). Such quantitative changes may appear not to parallel their associated cardiovascular benefits and have led some authors to posit related beneficial dietary effects. Both high-fibre and diets high in olive oil are rich in phytonutrient antioxidants that have been linked to reduced cardiovascular disease (Hjermann 1981, de Lorgeril 1994).

 

Sucrose, whilst not being associated with hyperglycaemia, is present in high amounts in high-carbohydrate diets and has been linked to advanced glycation end products and diabetes-associated cardiovascular disease (Howard 2002).

 

The loose concordance of the risk factors for diabetes and cardiovascular disease argue for an earlier interventionist approach and for treating both diseases independently. Tighter glycaemic control, through the use of drugs, above dietary measures and exercise, reduces the progress of the cardiovascular (Delahanty 1993, UK Prospective Diabetes Study 1998) as well as the microvascular and neurological complications of diabetes. That these protocols are not being pursued in a comprehensive manner is demonstrated by the fact that, in the US in recent years, there has been an increase in these complications (Koro 2004). Institution of these measures at an early stage to promote more adequate glycaemic control is therefore called for and illustrates the value of blood glucose measurement in diabetic management.

 

 

References

1. WHO (1998) Obesity: preventing and managing the global epidemic. Report of a WHO consultation on obesity. Geneva: World Health Organization

2. Diabetes Control and Complications Trial Research Group (1993) The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin dependent diabetes mellitus.  N Engl J Med  329: 977-86

3. Ohbuko Y, et al. (1998) Intensive insulin therapy prevents the progression of diabetic microvascular complications in Japanese patients with non-insulin-dependent diabetes mellitus: a randomized 6-year study. Diabetes Res Clin Pract 28: 103-117

4. UK Prospective Diabetes Study Group (1998) Intensive blood-glucose control with sulphonylureas or insulin compared to conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). Lancet 352: 837-53

5. Wilson PW (1998) Diabetes mellitus and coronary heart disease. Am J Kidney Dis 32: S89-S100

6. Grundy SM, et al. (1999) Diabetes and cardiovascular disease. A statement for healthcare professionals from the American Heart Association. Circulation 100: 1134-46

7. Diabetes Prevention Program (1999) Design and methods for a clinical trial in the prevention of type 2 diabetes. Diabetes Care 22: 623-34

8. Balkau B, et al. (1998) High blood glucose concentration is a risk factor for mortality in middle-aged nondiabetic men: 20-year follow up in the Whitehall Study, the Paris Prospective Study, and the Helsinki Policemen Study. Diabetes Care 21: 360-67

9. Despres JP, et al. (2001) Fat distribution and metabolism. Diabetes & Metabolism 27: 209-14 1

0. Chaturvedi N, Fuller JH (1995) Mortality risk by body weight and weight change in people with NIDDM. The WHO Multinational Study of Vascular Disease in Diabetes. Diabetes Care 18: 766-74

11. Brown AS,et al. (1996) Promoting weight loss in type II diabetes. Diabetes Care 19: 613-24

12. Heilbronn LK, Noakes M, Clifton PM (1999) Effect of energy restriction, weight loss, and diet composition on plasma lipids and glucose in patients with type 2 diabetes. Diabetes Care 22: 889-95

13. Foster GD, et al. (2003) A randomized trial of a low-carbohydrate diet for obesity. N Engl J Med 348: 2082-90

14. Franz MJ, et al. (1994) Nutrition principles for the management of diabetes and related complications. Diabetes Care 17: 490-518

15. Parillo M, Riccardi G (2004) Diet composition and the risk of type 2 diabetes: epidemiological and clinical evidence. Br J Nutr 92: 7-19

16. Riccardi G, Rivellese AA (2000) Dietary treatment of the metabolic syndrome - the optimal diet. Br J Nutr 83: S143-8

17. Garg A, et al. (1994) Effects of varying carbohydrate content of diet in patients with non-insulin-dependent diabetes mellitus. JAMA 271: 1421-8

18. Parillo M, Giacco R, Ciardullo AV, Rivellese AA, Riccardi (1996) Does a high-carbohydrate diet have different effects in NIDDM patients treated with diet alone or hypoglycemic drugs? Diabetes Care 19: 498-500

19. Storlein LH,et al. (1996) Dietary fats and insulin action. Diabetologia 39: 621-31

20. Mann JI (2002) Diet and risk of coronary heart disease and type 2 diabetes. Lancet 360: 783-89

21. Komiyama N, et al. (2002) The effect of high carbohydrate diet on glucose tolerance in patients with type 2 diabetes. Diabetes Research & Clinical Practice 57: 163-7

22. Yang EJ, et al. (2003) Carbohydrate intake and biomarkers of glycemic control among US adults: the third National Health and Nutrition Survey (NHANES III) Am J Clin Nutr 77: 1426-33

23. Jenkins DJ, et al. (2002) Glycemic index: overview of  complications in health and disease. Am J Clin Nutr 76: 266S-273S

24. Giacco R, et al. (2000) Long-term dietary treatment with increased amounts of 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: 1461-6

25. Chandalia M, et al. (2000) Beneficial effects of high dietary fiber intake in patients with type 2 diabetes mellitus. N Engl J Med 342: 1392-8

26. Brand-Miller J, Hayne S, Petocz P, Colagiuri S (2003) Low-glycemic index diets in the management of diabetes: a meta-anaysis of randomized controlled diets. Diabetes Care 26: 2261-7

27. Schulze MB, et al. (2004) Glycemic index, glycemic load, and dietary fiber intake and incidence of type 2 diabetes in younger and middle-aged women. Am J Clin Nutr 80: 348-356

28. Rizkalla SW, Bellisle F, Slama G (2002) Health benefits of low glycemic index foods, such as pulses, in diabetic patients and healthy individuals. Br J Nutr 88: S255-62

29. Garg A (1998) Dyslipoproteinemia and diabetes. Endocrinol Metab Clin N America  27:613-25

30. Vessby B, et al. (2001) Substituting dietary saturated for monounsaturated fat impairs insulin sensitivity in healthy men and women: the KANWU Study. Diabetologia 44: 312-9

31. Hjermann I, Holme I, Byre KV, Leren P (1981) Effect of diet and smoking intervention on the incidence of coronary heart disease. Lancet 1: 1305-10

32. de Lorgeril, et al. (1994) Mediterranean alpha-linolenic acid- rich diet in secondary prevention of coronary heart disease. Lancet 343: 1454-59

33. Howard BV, Wylie-Rosett J (2002) Sugar and cardiovascular disease: a statement for healthcare professionals from the Committee on Nutrition of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association. Circulation 106: 523-7

34. Delahanty LM, Halford BN (1993) The role of diet behaviors in achieving improved glycemic control in intensively treated patients in the Diabetes Control and Complications Trial. Diabetes Care 16: 1453-8

35. Koro CE, Bowlin SJ, Bourgeois N, Fedder DO (2004) Glycemic control from 1988 to 2000 among U.S. adults diabetes: a preliminary report. Diabetes Care 27: 17-20