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.




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