The dietitian’s role is to equip and assist people living with diabetes with the knowledge and confidence to make appropriate choices on the type and quantity of food they eat, thereby improving glycaemic control and overall quality of life. In addition, any dietary issues pertaining to comorbidities, such as coeliac disease and cystic fibrosis-related diabetes, are also addressed.

Dietary management of type 2 diabetes

The primary management strategy for people with type 2 diabetes who are overweight – between 80-90% of people with type 2 diabetes – or obese, is weight loss. Weight gain is positively associated with insulin resistance, therefore weight loss improves insulin sensitivity¹ and features of the metabolic syndrome, and lowers triglycerides. Intensification of therapy is often associated with weight gain depending on the drug of choice. Sulphonylureas are associated with a mean weight gain of 3kg and insulin initiation with 5kg.²

Newer medications such as the incretin-based therapies, exenatide and liraglutide, have been helpful in aiding weight loss causing increased satiety and having a known side-effect of nausea. Everyone with diabetes should ideally receive individual, ongoing nutritional advice or be offered structured education at the time of diagnosis with annual follow-up.³ Regular follow-up is essential to evaluate the effectiveness of change, help motivation and provide support, especially during times of relapse. Education is centred on the core areas of reducing total energy intake, monitoring total carbohydrate intake to achieve glycaemic targets and advising of the need for daily physical activity.

The largest amount of evidence in the literature is focused on the use of low-fat diets, the strategy most commonly utilised to induce weight loss. A recent trial in the US has shown that lifestyle interventions, including a low-fat diet, significantly reduced body weight, HbA1c and cardiovascular (CV) risk factors. The trial also showed that these changes could be maintained over a four-year period.⁴

Low glycaemic index diets have also shown small improvements in HbA1c of up to 0.5% and patients are therefore encouraged to eat carbohydrates of a low glycaemic index. Aerobic exercise improves glycaemia and lowers low-density lipoprotein (LDL) cholesterol by 5%,⁵ and resistance training has effects on both glycaemia and CV risk factors. For patients commencing insulin therapy, much emphasis is placed on maintaining current weight and preventing weight gain while glycaemic control improves.

Dietary management of type 1 diabetes

The main consideration for individuals with type 1 diabetes in terms of glycaemic control is the amount and type of carbohydrate consumed, which affects postprandial blood glucose. For individuals treated by multiple daily injections or continuous subcutaneous insulin infusion (insulin pump therapy), matching insulin dose to the quantity of carbohydrate consumed (carbohydrate counting and insulin dose adjustment) is a very effective strategy for improving and maintaining good glycaemic control. Randomised controlled trials have shown carbohydrate counting to be effective in improving glycaemia control, quality of life and general well-being⁶ without increasing severe hypoglycaemia, body weight or lipids.⁷

Patients can be taught carbohydrate counting and insulin dose adjustment on an individual basis or as a structured education programme over a number of days (Accu-Chek type 1 intensive insulin therapy, three-day course or dose adjustment for normal eating [DAFNE] five-day programme). 

For individuals on biphasic insulin regimes, consistency in the quantity of carbohydrate and glycaemic index on a day-to-day basis are all beneficial and have been positively associated with improved HbA1c levels. Sucrose does not affect glycaemic control of diabetes differently from other types of carbohydrates, and non-nutritive sweeteners are safe when consumed within the daily intake levels. 

Cardiovascular disease

Individuals with diabetes have a three to fourfold increase in CVD risk compared to those without diabetes.⁸ Daily consumption of foods fortified with plant stanols (2-3g/d) significantly improves total and LDL cholesterol for people with diabetes, irrespective of statin treatment.³ Consumption of oily fish, rich in n-3 unsaturated fats, is recommended at least twice per week and is associated with reduced incidence of, and deaths from, coronary heart disease.⁹

Current advice is to consume no more than 6g salt per day. A reduced salt intake in combination with the dietary approaches to stop hypertension (DASH) or Mediterranean-style diets can lower blood pressure.¹⁰ Weight loss (4.5kg or more) and exercise will also result in improvements to blood pressure and therefore patients must be encouraged to do both.

Management of hypoglycaemia

In individuals taking insulin or insulin secretagogues, changes in food intake, physical activity levels or medication, in addition to alcohol consumption, contribute to hypoglycaemia.

It is important for patients to learn to manage their diabetes to prevent hypoglycaemia. Therefore patients need to learn to adjust their insulin or carbohydrate intake where appropriate. The goal of treatment is to relieve hypoglycaemic symptoms while avoiding over-treating, which occurs all too frequently. Glucose is the preferred treatment, with a 10g and 20g dose of oral glucose increasing blood glucose levels by approximately 2mmol/l and 5mmol/l, respectively. 

In practice, patients are advised to consume 15g glucose and if blood glucose levels have not risen above 4mmol/l after 10-15 minutes to consume additional 15g glucose. A snack of 15-20g of carbohydrate may be necessary depending on individual circumstances. To take into consideration is how much active insulin is on board, what activity levels they have planned and when they are next likely to eat. Proactive steps need to be taken by the individual to minimise the risk of hypoglycaemia.

Additional considerations

Coeliac disease

Coeliac disease is more common in people who have an additional autoimmune condition such as type 1 diabetes. Individuals will require dietary advice with regard to a strict gluten-free diet in combination with their diet for diabetes.

Cystic fibrosis-related diabetes 

The prevalence of cystic fibrosis-related diabetes (CFRD) rises as the age of survival of CF patients increases and has features of both type 1 and type 2 diabetes. The onset is insidious, and glycaemic status varies as it is influenced by the clinical state of the person. The development of CFRD is associated with worse lung function and poorer nutritional status when compared to non-diabetic patients with cystic fibrosis. The diet should be high in energy, fat and with the planned use of refined carbohydrate. Conflicts between diet therapy for cystic fibrosis and diabetes should be resolved in favour of CF and insulin regimen adjusted to diet rather than diet to insulin. Therefore carbohydrate counting and insulin adjustment are useful tools to use for this patient group.

Pre-conception care

Women with type 1 or type 2 diabetes who are contemplating pregnancy should attend a specialist service. Strict glycaemic control is required prior to conception and women are recommended to take 5mg folic acid based upon the higher incidence of neural tube defects in infants of women with diabetes. The dietitian will play a role in achieving the required HbA1c while also ensuring the quality of the diet is one that will support a developing baby.

Chronic kidney disease

Diabetes is the single leading cause of end-stage renal disease worldwide. The role of the dietitian is to help to maintain optimal metabolic outcomes including glycaemic control, lipid profile, blood pressure, ideal body weight and biochemical parameters for potassium and phosphate, while also ensuring a nutritionally balanced diet.

Summary

Day-to-day dietetic practice within diabetes is varied, as outlined above, and is a rewarding area to practise in. Diet can be a source of bewilderment at times for individuals with diabetes. Therefore all individuals newly diagnosed with diabetes, where possible, should have early access to a dietitian with expertise in the area. 

References

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