Objective Nutrition therapy is an integral part of self-management education in patients with type 2 diabetes. Carbohydrates with a low glycemic index are recommended, but the ideal amount of carbohydrate in the diet is unclear. We performed a meta-analysis comparing diets containing low to moderate amounts of carbohydrate (LCD) (energy percentage below 45%) to diets containing high amounts of carbohydrate (HCD) in subjects with type 2 diabetes.
Research design and methods We systematically reviewed Cochrane library databases, EMBASE, and MEDLINE in the period 2004–2014 for guidelines, meta-analyses, and randomized trials assessing the outcomes HbA1c, BMI, weight, LDL cholesterol, quality of life (QoL), and attrition.
Results We identified 10 randomized trials comprising 1376 participants in total. In the first year of intervention, LCD was followed by a 0.34% lower HbA1c (3.7 mmol/mol) compared with HCD (95% CI 0.06 (0.7 mmol/mol), 0.63 (6.9 mmol/mol)). The greater the carbohydrate restriction, the greater the glucose-lowering effect (R=−0.85, p<0.01). At 1 year or later, however, HbA1c was similar in the 2 diet groups. The effect of the 2 types of diet on BMI/body weight, LDL cholesterol, QoL, and attrition rate was similar throughout interventions.
Limitations Glucose-lowering medication, the nutrition therapy, the amount of carbohydrate in the diet, glycemic index, fat and protein intake, baseline HbA1c, and adherence to the prescribed diets could all have affected the outcomes.
Conclusions Low to moderate carbohydrate diets have greater effect on glycemic control in type 2 diabetes compared with high-carbohydrate diets in the first year of intervention. The greater the carbohydrate restriction, the greater glucose lowering, a relationship that has not been demonstrated earlier. Apart from this lowering of HbA1c over the short term, there is no superiority of low-carbohydrate diets in terms of glycemic control, weight, or LDL cholesterol.
- Dietary Intervention
- Type 2 Diabetes
- Glycemic Control
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Contributors OS was the guarantor for conducting the study according to GRADE, data interpretation, producing tables and figures, and writing the manuscript. OS takes responsibility for the integrity of the data and the accuracy of the analysis. GMP assisted in the GRADE process and in the writing of the manuscript. HKA preformed the meta-analysis and assisted in the GRADE process and writing of the manuscript. AA contributed to the data analysis and the writing of the manuscript. All authors have reviewed and approved the revised manuscript.
Funding This research received no specific grant. OS received grant from the Danish Health Authority as the primary author of the Danish National Clinical Guideline for lifestyle intervention in type 2 diabetes.
Competing interests OS, GMP, and HKA report no competing interests. AA is a member of advisory boards/consultant for Lucozade Ribena Suntory, UK, McCain Foods Limited, USA, McDonald's, USA, Nestlé Research Center, Switzerland, Swedish Dairy, and Weight Watchers, USA. Outside the present paper, research conducted at his department is often funded by grants from interests in the food and beverage sector. Recipient of honoraria as Associate Editor, American Journal of Clinical Nutrition, and membership of the Editorial Boards of Annals of Nutrition and Metabolism, and of Annual Review of Nutrition. Recipient of travel expenses and/or modest honoraria (<$2000) for lectures given at national and international meetings, often with support from one or more corporate sponsors. Cofounder and co-owner of the University of Copenhagen spin-out companys Mobile Fitness A/S & Flaxslim ApS, Denmark. Recipient of royalties form a number of textbooks, and popular diet and cookery books. Coinventor of a number of patents owned by UCPH, in accordance with Danish law.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Supplementary data are available at the Danish Health Authority home page, PICO 4. (https://http://www.sst.dk/da/udgivelser/2015/nkr-type2diabetes).
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