The statement that introduced the first lecture I received as a dietetic student in 1973 and that I have heard repeated at various intervals over the past 30 years, usually to support the current thinking about the most effective dietary approach for treatment of diabetes, is:
‘Diet is a cornerstone in the treatment of diabetes.’
Diet remains a contentious issue for a number of reasons, most importantly because the majority of dietary advice we give our patients is not underpinned by hard evidence. It has been shown that nutritional therapy is an integral part of effective management of diabetes and has a vital role in helping people with diabetes achieve and maintain optimal glycaemic control (UKPDS, 1990; Delahanty, 1998), but there is little evidence to support the ‘best’ diet.
UK nutritional recommendations
The recommendations for people with diabetes are similar to the recommendations made for the general population, commonly known as a healthy diet (see Table 1, Table 2, Table 3). This entails adopting a reduced sugar, reduced fat and reduced salt diet that is high in fibre and with plenty of fruit and vegetables. There have been some changes in emphasis since the last published recommendations in 1992 (BDA, 1992) and these are summarised below (McGough, 2003).
A greater emphasis on the benefits of regular physical activity and weight management
Regular daily physical activity (as opposed to sessions of formal exercise) is of benefit to people with diabetes, regardless of body weight. Physical activity aids weight control, improves insulin sensitivity and lipid levels and maintains muscle mass (Lean and Haa, 1998).
The so-called ‘obesity epidemic’ has contributed to rising levels of diabetes around the world (Costacou and Mayer- Davis, 2003) and has led to emphasis upon weight management, especially amongst the 80% of those with type 2 diabetes who are obese. It has been shown that relatively small reductions of bodyweight have large metabolic benefits in people with diabetes; intentional weight loss of 9–13 kg results in a 25% reduction in the relative risk of mortality (Aucott et al, 2004).
Weight management is recommended through a combination of diet and increased physical activity. A reduction in energy dense foods is advised, especially those containing large amounts of fat and sugar. There is, as yet, no scientific evidence to support the use of low carbohydrate diets (e.g. the Atkins diet) in diabetes.
More flexibility in the proportion of monounsaturated fat and carbohydrate in dietary intake
Previous recommendations have advised that the diet should provide 50–55% energy as carbohydrate. In practice it is difficult for people with diabetes to increase carbohydrate intake to this level (Toeller et al, 1996) and the traditional UK diet provides only 45% of energy as carbohydrate. As carbohydrates cause postprandial increases in blood glucose, it is now recommended that there should be more flexibility in the amount of monounsaturated fat and carbohydrate in the diet. It is important that fat intake is modified to reduce the risk of vascular disease and that saturated (animal) fat is reduced to less than 10% of energy intake. Monounsaturated (olive oil, rapeseed oil) should be substituted for saturated fat and together with carbohydrate foods should make up the bulk of the diet (60–70% of energy). Fat is an energy dense nutrient and a reduction in intake is recommended for those individuals who would benefit from weight loss.
Sucrose (table sugar) no longer restricted to a specific amount
There is widespread belief that simple sugars like sucrose are digested and absorbed quickly and should be avoided and that complex carbohydrates like bread and potatoes are digested more slowly and should form the basis of the diet. It has now been well-established that sugar does not increase blood glucose levels more than starchy foods containing the same amount of carbohydrate. The total amount of carbohydrate eaten will determine postprandial blood glucose levels regardless of whether it is sugar or starch.
Traditionally table sugar (sucrose) has been restricted for people with diabetes. However, research supports the recommendation that sucrose can provide up to 10% of total energy intake (Slama et al, 1984) without compromising glycaemic control. Including sugar-containing foods should not result in an increase in overall energy intake, which will cause weight gain. Foods that contain large amount of sugar are often high in fat, e.g. chocolate, biscuits, cakes and are therefore energy (calorie) dense. People with diabetes who are overweight and who would benefit from weight loss should be advised to reduce sucrose-containing foods and drinks.
A recommendation to choose foods that have a low glycaemic index
The term glycaemic index (GI) was first coined in 1981 by Jenkins and is used to give an indication of the effect of carbohydrate foods on blood glucose levels. Foods with a low GI are digested and absorbed more slowly than foods with a high GI. Low GI foodstuffs are recommended for people with diabetes. Short-term studies have shown beneficial effects on both glycaemia and lipid profiles in people with diabetes (Frost et al, 1994). Table 4 shows the GI of some common foods.
Table 1 shows that the theoretical nutritional recommendations are made in terms of nutrients and not foods, and the skill of the dietary practitioner lies in translating this theory into practice. The practical applications are shown in Table 3. Although these recommendations are based upon the available evidence, it is important to remember that they are not rigid targets that should be imposed on every individual with diabetes regardless of personal circumstances. Most people diagnosed with diabetes will never achieve the ideal diet and patterns of physical activity. They should be encouraged to make specific changes to their diet and activity that move towards the ideal recommendations. These changes must be negotiated for each individual and take into account factors like meal patterns, personal food preferences, culture, medication and lifestyle.
Delivering dietary advice
Ideally, dietary information should be delivered by a diabetes specialist dietitian (BDA, 1999). However, there are too few specialist dietitians to provide individual advice for all (Nelson et al, 2000) and the predicted increase in type 2 diabetes will exacerbate this. In practice, many people who are diagnosed with diabetes will receive dietary advice from the primary healthcare team and from specialist nurses. It is of paramount importance that all members of the diabetes team delivering dietary advice are updated on recent changes and that they deliver a consistent message to people with diabetes.
The focus of dietary counselling deserves consideration. The majority of dietary interventions still concentrate upon what should be done (reduce fat, increase fruit and vegetables, etc) rather than how dietary change may be achieved (counselling skills, empower patients, motivational interviews). Most people
make decisions about their food intake for reasons other than health or because they have diabetes and these reasons must be addressed for successful counselling. Dietary advice must consider the individual’s wishes and willingness to change and should address personal, cultural and religious preferences and take into account the individual’s beliefs and lifestyle. This is often referred to as the empowerment model and there is mounting evidence to support this approach to chronic disease management (Anderson, 2000).
Healthcare professionals are trained in the traditional concept of the acute medical model, and feel it is their responsibility to help their patients achieve tight glycaemic control to minimise the risks of complications. However, they have no control over the lifestyle behaviours that their patients choose to adopt and this leads to frustration, dissatisfaction and patient-blaming.
Application of the empowerment model aims to maximise the skills, knowledge and sense of personal autonomy to allow people to take charge of their own diabetes self-management. It is a collaborative process leading to informed decisions by the person with diabetes and does not rely on the traditional view of the healthcare professional as the expert. Empowerment means a more positive experience for the patient and healthcare professional alike and is more likely to result in meaningful behaviour change.
The recently published nutritional recommendations from Diabetes UK (2003) stress the importance of individual implementation of evidence-based dietary advice for people with diabetes. These recommendations are not based on a one- size fits all approach and should be interpreted in light of the wishes and needs of the person with diabetes. The focus of counselling the person with diabetes should include both the two domains of knowledge (what is said) and awareness of the patients needs (how it is said). Most people with diabetes choose similar health-related goals to healthcare professionals – improved glucose, lipid and blood pressure levels, weight loss and increased physical activity levels and as they become empowered are more likely to achieve these goals.