Although the nutritional recommendations for people with Type 1 and Type 2 diabetes are in essence the same, there may be a difference in emphasis.
Cardiovascular disease is the main cause of mortality in both Type 1 and Type 2 diabetes, so restriction of saturated fat is a prime aim for all people with diabetes.
However, there should be greater emphasis on modification of fat intake for people with Type 2 diabetes where lipid abnormalities are more common.
People with diabetes who are overweight or obese have a wide range of complications of their obesity: more symptoms can be related to BMI (body mass index) than can be related to blood glucose, so weight management is a fundamental aspect of treatment in Type 2 diabetes.
For Type 1 diabetes greater emphasis should be placed on attempts to modify the progression of microvascular disease, especially nephropathy, by restricting protein intake.
The ultimate goals of management depend on the priorities relevant to the individual person with diabetes.
ENERGY BALANCE AND BODY WEIGHT
Obesity is recognised as a leading cause of insulin resistance (21).
It therefore contributes to the development of Type 2 diabetes.
This is particularly true for a central distribution of body fat, associated with a range of metabolic disturbances.
Weight management is crucial in controlling blood glucose levels in people with Type 2 diabetes, although from UKPDS there is evidence that to normalise glucose tolerance usually requires major weight loss.
Studies suggest that at least 80% of newly diagnosed patients with Type 2 diabetes are overweight and weight loss in people with Type 2 diabetes who are overweight increases life expectancy.
Obesity is an additional risk factor for coronary heart disease and stroke.
All cardiac risk factors (glycaemia, hypertension, lipids) are improved with weight management (22).
This is true for individuals with Type 1 diabetes as well as Type 2 diabetes.
However, it is also important to make sure that energy requirements are adequate in children and adolescents with Type 1 diabetes.
Dietary strategies for weight management should be based on realistic target weights.
Assessment of target weights and the appropriate level of energy
6 NUTRITIONAL MANAGEMENT OF DIABETES MELLITUS
Table 1.1
Age range (yr) BMR (kcal/day) Activity level 24-h Energy expenditure (kcal/day)
Men 10, 18 17.5W+651 Inactive BMR1.30 18, 30 15.3W+679 Light BMR1.55 30, 60 11.6W+879 Moderate BMR1.78 4 60 13.5W+487 Heavy BMR2.10
Women 10, 18 12.2W+746 Inactive BMR1.30 18, 30 14.7W+496 Light BMR1.56 30, 60 8.7W+829 Moderate BMR1.64 4 60 10.5W+596 Heavy BMR1.82 W ¼ weight (kg).
restriction is not a precise science.
Equations are available for estimating basal metabolic rate and daily energy expenditure from body weight in kilograms and activity level, when prescribing calorie-controlled diets (23), see Table 1.1.
In general, long-term lifestyle changes and strategies are more likely to result in sustained weight loss.
Realistic calorie deficits of 500 kcal/day usually produce better end results than very restrictive diets (24).
Strategies to support individuals trying to lose weight may range from individual counselling to group therapy.
The use of very low calorie diets (VLCDs) in people with diabetes has however been shown to have positive effects on plasma lipids, lowering triglyceride levels and raising HDL cholesterol (25).
Most of the benefits relate to energy restriction not weight loss (26).
Although more weight is lost over a 3, 6 month period than using conventional diets there is no evidence that in the long term (1, 2 years) the continued benefit of using VLCDs is maintained.
VLCDs should only be used in a specialist setting as complications of VLCD therapy can include alterations in body composition including bone loss and possibly loss of cardiac muscle (27).
As a generalisation the use of anti-obesity drugs should be restricted to specialist medical centres in the absence of large-scale studies of their application in diabetes.
The Royal College of Physicians (28) produced guidelines for the use of anti-obesity drugs for obesity treatment.
Individuals who are overweight should have the necessary advice and support to reduce their calorie intake and to increase their energy expenditure in order to shift their energy balance and weight in the direction of a more ideal BMI.
Sustained weight loss and prevention of weight regain are important goals which are preferable to more rapid weight loss which usually results in excessive loss of lean body mass.
Even modest weight loss confers benefits to health (29).
Whenever possible those people who are overweight should be
NUTRITIONAL RECOMMENDATIONS IN DIABETES MANAGEMENT 7
offered a multi-disciplinary structured approach to weight management.
Dietary advice should take into account an increase in physical activity, which may also facilitate weight loss and help to maintain muscle mass.
Normally, people’s appetites increase with exercise automatically.
However, for those with Type 1 diabetes adequate or additional carbohydrate before, during and after exercise as well as insulin adjustment needs to be anticipated, see Chapter 2.
For those people with Type 2 diabetes on oral hypoglycaemic therapy, adjustment of medication is usually not necessary unless on sulphonylureas where hypoglycaemia may be a risk with sustained exercise.
The level of activity will depend on age and degree of fitness but moderate activity (walking) for at least 20, 30 min a day will be beneficial.
Adjustment of medication for both Type 1 and Type 2 may be necessary if weight loss occurs and is maintained in the long term.
MACRONUTRIENT COMPOSITION OF THE DIET
The main dietary components of the diet for an individual with diabetes should be carbohydrate-containing foods with a low glycaemic index and cis- monounsaturated fat.
Although it is important to give people with diabetes advice to modify their dietary intakes so that they shift the balance of their nutritional intake in the direction of the recommendations, the relative proportions of macronutrients may vary depending on the markers of diabetes control for the individual.
A combination of carbohydrate and cis-monounsaturated fatty acids should provide 60, 70% total daily energy intake.
Total fat intake should be restricted to 35% total energy.
Cis-monounsaturated fatty acids should provide between 10 and 20% total energy.
Saturated and trans-fatty acids should provide under 10% total energy.
Polyunsaturated fatty acids should not exceed 10% total energy.
Protein intake should range between 10 and 20% total energy.
Protein intake should not go below 0.6 g/kg normal body weight/day but should be at the lower end of the range (0.8 g/kg body weight/day) in cases of nephropathy or where abnormal microalbuminuria has been identified.
The relative proportions of macronutrients recommended in diabetes
Protein (10, 20%) Carbohydrate (45, 60%) Cis-monounsaturated fat (10, 20%) Polyunsaturated fat (5 10%) Saturated/trans fat (5 10%)
8 NUTRITIONAL MANAGEMENT OF DIABETES MELLITUS
CARBOHYDRATE
The proportion of energy derived from carbohydrate is related to the level of fat intake.
Recommendations in the past have tended to be narrow and precise with regard to fat and carbohydrate intake.
Although good diabetes control can be achieved with a range of carbohydrate intake (45, 60%), it can be difficult to maintain a high-carbohydrate/low-fat balance in practical terms.
The current emphasis is on a more flexible approach dependent upon the individual’s lifestyle, habits and diabetes management.
To minimise the risk of hypertriglyceridaemia and an associated increased risk for cardiovascular disease, high-carbohydrate diets for people with diabetes should incorporate a high intake of soluble fibre and resistant starch (30).
In cases where a lower carbohydrate intake is optimal for control and lifestyle, intake of energy from monounsaturated fat can be increased, as long as calorie control is monitored.
GLYCAEMIC INDEX
The glycaemic index (GI), see Chapter 11, was proposed as a method to guide food selection in the early 1980s by Jenkins and colleagues.
It is based on the assessment of carbohydrate foods in terms of glycaemic response compared to the same amount of a standard carbohydrate-containing food (usually bread or glucose) (31).
The GI of a food is determined by a number of factors, including the rate of digestion and absorption.
The soluble fibre content as well as the structure of the food and other meals and foods consumed as part of the overall diet are all significant influences on the glycaemic index of a particular food (32).
FIBRE
Dietary fibre or non-starch polysaccharides may broadly be classed as soluble fibre (gums, gels and pectins) and insoluble fibre (cellulose and lignin). There is epidemiological evidence that low intakes of insoluble fibre are associated with an increased risk of Type 2 diabetes (33). In general, the benefits of insoluble fibre are limited to promoting healthy gut functioning. The intake of soluble fibre is however beneficial to glycaemic and lipid control (34).
NUTRITIONAL RECOMMENDATIONS IN DIABETES MANAGEMENT 9
SUGAR AND SWEETENERS
SUCROSE The diabetic diet has in the past been referred to as the sugar-free diet but many studies have shown that consuming iso-caloric amounts of other carbohydrates can raise blood glucose levels and aggravate hyperglycaemia more than sucrose itself (35,36). The consensus view is that sucrose may be consumed in the diet of people with diabetes at the same level, 10% of total calories, as that recommended for the general population.
FRUCTOSE Fructose has been shown to invoke a lower glucose and insulin response compared to other carbohydrates (37).
However, dietary fructose in amounts comparable to those of sugars in Western diets (7.5, 20% daily energy) can result in raised fasting triglycerides and LDL concentrations.
There may also be a greater risk of gastrointestinal disturbances with large doses (38).
There is no reason to believe that fructose either confers special benefits for people with diabetes or that it is detrimental to health in the amounts found in everyday foods.
NUTRITIVE SWEETENERS Polyols or sugar alcohols like sorbitol, xylitol, mannitol and isomalt are bulk or nutritive sweeteners which contain calories and raise blood glucose levels.
They must still be accounted for in meal planning.
They have a slightly lower glycaemic response than sucrose and a slightly lower calorie value (2.4 kcal/g) because they are not completely digested and absorbed.
Polyols may therefore cause diarrhoea, particularly if consumed in large amounts (4 25 g).
Although they have a lower cardiogenic effect compared to sucrose, polyols offer no special benefit to people with diabetes.