Nutrition management is fundamental for the prevention of type 2 diabetes and effective management of type 1 and type 2 diabetes. The aim is for people with diabetes to obtain the knowledge, skills and confidence to make appropriate food choices to reduce risk, improve glycaemic control and quality of life.
With new diagnostic criteria anticipated to increase the number of people diagnosed with diabetes in the UK by a third, structured evidence-based dietary education will be an effective way to save on medical costs for prescription drugs.1
Nutrition therapy has led to reductions in HbA1c of 1-2 per cent in people with newly diagnosed and existing type 2 diabetes.2 Dietary interventions can improve glycaemic control whilst also halting and even reversing progression of beta-cell failure and insulin resistance, thus reducing medication use in type 2 diabetes.3-5 Nutrition therapy can result in reduced health service utilisation and costs, and the savings may actually exceed the cost of providing the service.1,6
Intensive nutrition therapy has resulted in weight loss and improved glycaemic control at six months,5 12 months3 and four years.7 When insulin resistance dominates, weight loss is an effective strategy that increases insulin sensitivity, improving glycaemic control.8
Carbohydrate and fibre
Carbohydrate is the only nutrient that has a direct effect on blood glucose levels. Following a meal, blood glucose is determined by its rate of absorption and clearance.9 Quantity of carbohydrate is the key factor for optimal glycaemic control and emerging research supports carbohydrate-restricted diets in the management of type 2 diabetes but robust RCTs are required to assess the long-term effect.10
Quality (type) of carbohydrate may have an additional benefit on glycaemia over that observed when total carbohydrate is considered alone. Starchy carbohydrates can affect blood glucose more rapidly than fructose, sucrose or lactose, and sucrose intakes of 10-35 per cent of total energy do not negatively affect blood glucose when substituted for isocaloric amounts of starch.8
Dietary fibre may attenuate the insulin response to a meal by delaying glucose uptake. Viscous fibres (e.g. guar gum, beta-glucan, pectins) appear to significantly reduce the glucose response to a meal.11Consumption of whole grain foods lowers postprandial plasma glucose and insulin response; higher intake of whole grains is also associated with decreased insulin resistance.12 However, there is limited evidence that diets providing 30-50g fibre per day consistently lower blood glucose.8
Protein and fat
Dietary protein has no direct effect on glycaemia; however, it acutely stimulates insulin secretion and improves insulin sensitivity.13 The results with regard to the action of protein on glycaemia are conflicting and further research is required.
Dietary fat slows glucose absorption, delaying peak glycaemic response to the consumption of carbohydrate. However, the glucose area under the curve remains the same.10,14
There is some evidence that if monounsaturated and polyunsaturated fat replace saturated fat (SFA) then pancreatic beta-cell function, insulin sensitivity and glucose uptake are promoted; whereas higher intakes of SFA and trans-fatty acids impair glucose metabolism and increase insulin resistance.13,14
There is strong evidence that reducing SFA is beneficial to health but the optimal strategy to replace energy from SFA is unclear. Further good quality clinical trials are required.
- People with diabetes should receive personalised nutritional education from an appropriately trained healthcare professional, as a series of one-to-one consultations or as part of a structured educational programme.15
- Weight loss is recommended for all overweight or obese individuals who have diabetes.16,17 Although the optimal dietary approach to weight loss has yet to be identified, a realistic target is to aim for a weight loss of 5-10 per cent of body weight.8,18
- Monitoring carbohydrate is a key strategy in achieving glycaemic control; use of the glycaemic index may provide modest additional benefits for blood glucose control. Sucrose-containing foods can be substituted for other carbohydrates. Carbohydrate intake should be consistently distributed through the day in people receiving lifestyle advice alone or taking oral hypoglycaemics. Those on basal bolus insulin may adjust mealtime insulin doses to match carbohydrate intake.8,16
- The UK recommended daily intake for fibre is 24g.19
- The UK recommended daily intake for protein is 45g for an adult woman and 55g for an adult man (constituting 8-9 per cent of total calories).19 However, usual intake (75-100g for an adult woman and 94-125g for an adult man, or 15-20 per cent of daily total calories) should not be discouraged in those with normal renal function.
- SFA should be reduced and replaced with unsaturated fat, preferably monounsaturated fats.8,16 UK recommended daily intake is 20g SFA and 70g total fat for women based on a 2,000 calorie diet and 30g SFA and 95g total fat for men based on a 2,500 calorie diet.19
Dr Deakin is a consultant diabetes dietitian for the charity X-PERT Health
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