Background
Diabetes UK has been formulating and publishing dietary guidelines regarding diabetes for the past 36 years, with revisions and updates at roughly 10-year intervals. Each revision has attempted to reflect current practice and evidence, although the move from expert consensus and opinion to evidence-based guidelines was not made until 2011, reflecting the increase in the amount and quality of dietary intervention studies in people with diabetes over the past 15 years.
The latest guidelines, launched at the Diabetes UK Professional Conference in March 2018 and published simultaneously [1, 2], are evidence based and, although they are based upon previous guidelines, they differ in a few key areas.
- The new guidelines stress the importance of tailoring dietary advice to individuals.
- The guidelines are based on food rather than on nutrients, designed to support both delivery and understanding of dietary recommendations.
- Sections have been added or enlarged to reflect current practice and guidance, including subjects such as education in ethnic minority groups, pregnancy, and the prevention of type 2 diabetes.
The guidelines were formulated using evidence from both randomized controlled trials and prospective cohort studies and the Grading of Recommendations Assessment, Development and Evaluation system was used to assess individual recommendations [3].
Relevance of the new guidelines to primary care
The new guidelines cover all dietary aspects of diabetes prevention and management, although certain areas, such as the nutritional management of cystic fibrosis-related diabetes and enteral feeding, are not relevant to primary care and will not be discussed further here.
The key features for primary care are diabetes education, type 2 diabetes prevention, management of type 1 and type 2 diabetes, and cardiovascular risk reduction.
… it appears that the type of fat, rather than the total amount, is a key feature.
Diabetes education
Structured education programs have demonstrated efficacy and cost-effectiveness for people with type 1 and type 2 diabetes, and in diabetes prevention. Both Diabetes UK and the National Institute for Health and Care Excellence (NICE) recommend referral to structured education programs for all people with diabetes and for those at risk of type 2 diabetes. It is recommended that all education programs comply with NICE criteria [4], and a voluntary accreditation program has been introduced to ensure standards are maintained [5].
Type 2 diabetes prevention: What the data tell us
There is now strong evidence that multicomponent behavioral lifestyle programs can reduce the risk of type 2 diabetes by approximately 50% in those with prediabetes. The most dominant predictor of diabetes prevention is weight loss, and this is usually achieved through a combination of diet and increased physical activity. Most studies have used a healthy eating strategy, including portion control to induce weight loss, moderate fat intake (<35% total energy intake), reduced saturated fat intake (<10% total energy intake) increased dietary fiber (>15 g/1000 kcal), and increased moderate or vigorous physical activity aiming for 150 minutes per week. In England, referral to the National Health Service Diabetes Prevention Program is recommended for those at risk of diabetes, and a recent audit reported that over 43,000 referrals were received between June 2016 and March 2017, although only 49% of the referred patients attended the initial assessment [6]. Early results report that mean weight loss in the 2277 people who have completed the program to date was 3.7 kg [7].
Management of type 1 diabetes: Glycemic control
Carbohydrate is the key nutritional consideration for those with type 1 diabetes, and it is recommended that structured education is offered to support carbohydrate-counting and insulin adjustment in individuals using multiple daily injection or pump therapy. For those on fixed insulin injection therapies, a consistent amount of carbohydrate on a day-to-day basis is recommended.
Management of type 2 diabetes: Weight reduction
Weight reduction is emphasized as the key component of management in the 90% of people with type 2 diabetes who are overweight or obese. A new recommendation about diabetes remission is based on evidence from the DiRECT study, which reported that 47% of people diagnosed with diabetes for less than 6 years experienced diabetes remission at 12 months' follow-up [8]. The participants in the intervention group received at least 12 weeks of total diet replacement (liquid formula diet providing approximately 800 kcal/day) followed by a structured food introduction and weight maintenance program. Further analysis showed that diabetes remission was directly related to the amount of weight lost, resulting in a recommendation that ≥15 kg weight loss should be achieved to maximize the chance of remission.
For those with established diabetes, where remission is less likely, weight loss of at least 5% is recommended to improve glycemic control and reduce cardiovascular risk. There is little or no evidence to suggest that there is an ideal strategy for weight loss in people with type 2 diabetes as most studies have shown a positive effect of intervention whatever dietary approach is applied. For this reason, the new guidelines recommend tailoring advice to the individual and offering a choice of dietary strategies for weight loss, incorporating portion control and including low-fat diets, low-carbohydrate diets, Mediterranean-style diets, low-calorie diets, meal-replacement plans, and commercial providers, preferably as part of a multicomponent behavioral lifestyle program. The latest evidence suggests that the degree of adherence is a greater prediction of successful weight loss than the type of diet [9], and it is certainly intuitive that an individual is more likely to adhere to a diet that suits their lifestyle and includes food they enjoy.
Although weight loss is recommended as a primary strategy for those who are overweight and obese, carbohydrate management is also advised to improve glycemic control. There is no evidence for an optimum amount of carbohydrate in the diet, and recommendations should be made on an individual basis. There are various tools and resources available to quantify carbohydrate intake, including food models, food plates, and handy guides to portion size, and these are usually incorporated into structured education programs. The new guidelines also recommend that a reduction in carbohydrate may be considered to improve glycemic control, but there is no evidence to support low-carbohydrate diets as first-line therapy for those with type 2 diabetes [10].
Cardiovascular risk reduction
Studies have indicated little benefit of low-fat diets for cardiovascular disease risk reduction in people with diabetes, and it appears that the type of fat, rather than the total amount, is a key feature. The new guidelines continue to recommend reducing saturated fat and replacing it with unsaturated fat (either polyunsaturated or monounsaturated), as there is strong evidence of efficacy for cardiovascular risk reduction [11]. Dietary patterns that are associated with reduced risk include Mediterranean-style diets, “healthy eating” diets, and the “dietary approaches to stop hypertension” diet [12], all of which can be recommended. Specific foods that are associated with reduced risk include oily fish, olive oil, fruit and vegetables, and wholegrain foods.
Summary
The new Diabetes UK guidelines support the prevention and management of diabetes by recommending healthful dietary patterns and specific foods. Diabetes education is a key component of the recommendations, and the emphasis for prevention, remission, and management of type 2 diabetes is weight loss.