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Diabetes and sugary foods

Key learning points:

 - Sugar reduction alone should not be the primary focus of dietary advice for type 2 diabetes

 - Weight management is the key to improving blood glucose control

 - Dietary approaches to reduce cardiovascular risk are effective and important

Dietary advice for type 2 diabetes in primary care often focuses on reducing obvious sources of sugar in the diet. Although this is appropriate for those patients who are consuming excessive quantities of foods or drinks high in sugar, it fails to provide patients with a more complete explanation for the fluctuations in blood glucose that may result from their dietary choices. This article aims to give readers a brief overview of dietary approaches in type 2 diabetes, concentrating on the management of blood glucose. 

The importance of diet in the management of type 2 diabetes cannot be underestimated. Nutrition interventions in diabetes have demonstrated reductions in HbA1c of between 0.5% and 2.3%,1 which rival the reductions seen with some anti-hyperglycaemic drug treatments. However, there are a range of different dietary approaches which may be effective in controlling blood glucose, including low fat, low carbohydrate, low glycaemic index, high protein and Mediterranean diets.2 

The current quality and outcomes framework (QOF)3 incentivises referral to structured education programmes (DM014) and dietary review by a “suitably competent professional” (DM013). Diabetes UK and The British Dietetic Association jointly issued a briefing document in May 2013 which outlines the competencies required for DM013.4

Why weight? 

Studies suggest that 60-90% of type 2 diabetes is related to obesity5,6 and that simple lifestyle measures including modest weight loss (about 5-7% of body weight) can lead to a reduction in progression to type 2 diabetes of 58%.7 More recently, temporary reversal of diabetes has been seen with the use of very low energy diets (VLEDs), consisting of about 600kcal per day.8 In research studies comparing different dietary approaches, the common denominator in producing successful outcomes is weight loss. Reducing insulin resistance is one of the mechanisms through which weight loss is thought to be effective. Current evidence for controlling blood glucose in type 2 diabetes suggests reducing calorie intake and losing weight should be the priority.9 It is important that patients understand why there is so much focus on weight loss, and that losing weight can have a dramatic effect on their blood glucose control. 

Which nutrients affect blood glucose?

Although weight loss is the primary focus for blood glucose management, food choices themselves can have a significant impact. Most foods consist of a combination of the three major nutrients: fat, protein and carbohydrate. Fat and protein have no direct or immediate effect on blood glucose, but should be considered as part of a healthy, balanced diet. Carbohydrate, however, is the key nutrient affecting blood glucose and there is much confusion over this aspect of the diet. It's helpful for patients to be able to recognise sources of this nutrient from familiar foods, and to understand that the total quantity of carbohydrate-containing foods eaten will have the greatest impact on the blood glucose. A 'healthy' diet that does not consider the quantities of carbohydrate will be unlikely to benefit patients' blood glucose control. 

What is Carbohydrate?

Carbohydrate-containing foods include all 'starchy' foods and all 'sugary' foods (both naturally-occurring and added sugars). Both starchy and sugary carbohydrate foods have the same potential to raise blood glucose, and the quantity eaten will determine by how much. So these foods need to be considered both as part of a healthy, balanced diet, and for their effect on blood glucose. 

How much carbohydrate?

The ideal quantity of carbohydrate for people with diabetes is the subject of debate and controversy. Decades ago carbohydrate was restricted in diabetes and, until recently, some organisations were advocating 'plenty of starchy carbohydrate'. There is in fact no consensus in the research literature and studies show benefits for a wide range of quantities of carbohydrate in the diet for type 2 diabetes.10-15.There is evidence that reduced-carbohydrate diets may be of benefit for weight loss in type 2 diabetes.12 Due to the importance of weight management, the limited evidence for the optimum quantity of carbohydrate, and the fact that most people with type 2 diabetes struggle with losing weight, portion size in general is probably the key. Secondary to the quantity is the type of carbohydrate. In other words, different carbohydrate-containing foods will cause the blood glucose to rise at different rates. This is known as the 'glycaemic index' (GI). 

Glycaemic Index

Choosing slower-acting carbohydrate (low GI) foods can offer an additional benefit in controlling blood glucose; an estimated 0.5-0.8% reduction in HbA1c.16,17 The term 'glycaemic load' (GL) refers to the combined impact of both the quantity of carbohydrate and rate at which the food will cause the blood glucose to rise (GI). 

Glycaemic index is a potentially complex and confusing concept for patients and professionals alike, as the GI of a food is not necessarily related to whether it is starchy or sugary, and gone are the terms 'simple' and 'complex' carbohydrates as they do not accurately reflect the nature of GI. For example, the GI of a chocolate bar is lower than the GI of white bread. This doesn't mean we should be advising our patients to avoid white bread and eat chocolate instead, but it does illustrate the counter-intuitive nature of GI when it is taken out of context. It may be helpful to simply refer to 'slower-acting' foods that can help to control blood glucose, when discussing this concept with patients. There are a number of higher GI foods that can be replaced by slower-acting alternatives that also have other health benefits, as shown in the examples in Table 1. 

The GI is of particular relevance in the treatment of hypoglycaemia, the aim of which is to raise blood glucose as quickly as possible. As such, high-GI foods (eg. jelly sweets, non-diet carbonated drinks, glucose tablets) are recommended as hypo treatments and lower-GI foods, such as chocolate and biscuits, are not suitable. 

Artificial sweeteners

Research evidence for the impact of artificial sweeteners on HbA1c is limited, however there is evidence that they may contribute to a reduction in calorie intake and as such be of use to those wishing to lose weight.18 A simple switch from sugar-sweetened beverages to artificially-sweetened drinks will likely bring the greatest benefit. Drinks labelled 'diet' or 'zero' are typically sugar-free. 

Heart health

Achieving control of blood glucose will of course improve risks for all diabetes complications; however there are a number of dietary measures that can be taken to help reduce cardiovascular risk. More details can be found in the UK Evidence-Based Nutrition Guidelines for the Prevention and Management of Diabetes.9

This article aimed to stimulate some thoughtful reflection with respect to the advice offered to patients with type 2 diabetes. A more comprehensive understanding of the relationship between food choices, body weight and blood glucose would be of benefit to this patient group. 

Resources

The British Dietetic Association

Diabetes Management & Education Group of The BDA

Nutrition & Dietetic Resources (UK)

Diabetes UK

 

References

 1. Franz MJ, Powers MA, Leontos C, Holzmeister LA, Kulkarni K, Monk A, et al. The evidence for medical nutrition therapy for type 1 and type 2 diabetes in adults. J Am Diet Assoc 2010;110(12):1852-89. 

 2. Ajala O, English P, Pinkney J. Systematic review and meta-analysis of different dietary approaches to the management of type 2 diabetes. The American journal of clinical nutrition 2013;97(3):505-16. 

 3. NHS Commissioning Board. Quality and Outcomes Framework guidance for GMS contract 2013/14. London: NHS Commissioning Board; 2013.

 4. Diabetes Management Group (DMEG) of the BDA. Nutrition and Physical Activity Diabetes Competencies briefing document. London: 2013.

 5. Anderson JW, Kendall CW, Jenkins DJ. Importance of weight management in type 2 diabetes: review with meta-analysis of clinical studies. J Am Coll Nutr 2003;22(5):331-9. 

 6. Chan JM, Rimm EB, Colditz GA, Stampfer MJ, Willett WC. Obesity, fat distribution, and weight gain as risk factors for clinical diabetes in men. Diabetes Care 1994;17(9):961-9. 

 7. Walker KZ, O'Dea K, Gomez M, Girgis S, Colagiuri R. Diet and exercise in the prevention of diabetes. Journal of human nutrition and dietetics: the official journal of the British Dietetic Association 2010;23(4):344-52. 

 8. Lim EL, Hollingsworth KG, Aribisala BS, Chen MJ, Mathers JC, Taylor R. Reversal of type 2 diabetes: normalisation of beta cell function in association with decreased pancreas and liver triacylglycerol. Diabetologia 2011;54(10):2506-14. 

 9. Dyson PA, Kelly T, Deakin T, Duncan A, Frost G, Harrison Z, et al. Diabetes UK evidence-based nutrition guidelines for the prevention and management of diabetes. Diabet Med 2011;28(11):1282-8. 

 10. Kirk JK, Graves DE, Craven TE, Lipkin EW, Austin M, Margolis KL. Restricted-carbohydrate diets in patients with type 2 diabetes: a meta-analysis. J Am Diet Assoc. 2008;108(1):91-100.

 11. Kodama S, Saito K, Tanaka S, Maki M, Yachi Y, Sato M, et al. 

Influence of fat and carbohydrate proportions on the metabolic profile in patients with type 2 diabetes: a meta-analysis. Diabetes Care 2009;32(5):959-65. 

 12. Nield L, Moore H, Hooper L, Cruickshank K, Vyas A, Whittaker V, et al. Dietary advice for treatment of type 2 diabetes mellitus in adults. Cochrane Database of Systematic Reviews [Internet]. 2007; (3). Available at: http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD004097.pub4/abstract.

 13. Wheeler ML, Dunbar SA, Jaacks LM, Karmally W, Mayer-Davis EJ, Wylie-Rosett J, et al. Macronutrients, Food Groups, and Eating Patterns in the Management of Diabetes. Diabetes Care 2010;35:

434-45.

 14. Nisak M, Talib R, Norimah AK, Gilbertson H, Azmi K. Improvement in Dietary Quality with the Aid of a Low Glycaemic Index Diet in Asian Patients with Type 2 Diabetes Mellitus. American Journal of Clinical Nutrition 2011;29(3):161-70.

 15. Larsen RN, Mann NJ, Maclean E, Shaw JE. The effect of high-protein, low-carbohydrate diets in the treatment of type 2 diabetes: a 12 month randomised controlled trial. Diabetologia 2011;54(4):731-40. 

 16. Brand-Miller J, Hayne S, Petocz P, Colagiuri S. Low-glycemic index diets in the management of diabetes: a meta-analysis of randomized controlled trials. Diabetes Care 2003;26(8):2261-7. 

 17. Fabricatore AN, Wadden TA, Ebbeling CB, Thomas JG, Stallings VA, Schwartz S, et al. Targeting dietary fat or glycemic load in the treatment of obesity and type 2 diabetes: a randomized controlled trial. Diabetes Res Clin Pract. 2011;92(1):37-45. 

 18. Fitch C, Keim KS. Position of the Academy of Nutrition and Dietetics: Use of Nutritive and Nonnutritive Sweeteners. Journal of the Academy of Nutrition & Dietetics 2012;112(5):739-58.