Low Carbohydrate Diets for Diabetes: A Review of the Clinical Effectiveness and Guidelines

Key Message

Ten systematic reviews (SRs) with eligibility criteria broader than this report were identified and network meta-analyses (NMAs) were included in three of them. Four evidence-based guidelines were identified. There were no direct comparisons between low-carbohydrate and standard diets in the primary studies in the SRs. Indirect comparisons between low-carbohydrate and standard diets were available in three NMAs with different scopes. One NMA found that low carbohydrate diets were significantly more effective in reducing triglyceride levels compared with the control diets, but insignificant for low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol levels. Another NMA included fewer primary studies in the NMA and concluded that low-carbohydrate diets were not significantly effective to reduce the levels of glycated hemoglobin (HbA1c), total cholesterol, and BMI, and increasing HDL cholesterol levels. The other NMA found low-carbohydrate diets significantly more effective in reducing HbA1c and fasting glucose levels.The American Diabetes Association (ADA) guideline provides a recommendation that there is no single ideal dietary distribution of calories and individualized plans should be made. In the other recommendation, various diets are acceptable for the management of type 2 diabetes and low-carbohydrate diets are mentioned in the evidence review.The Diabetes Canada guideline recommends that carbohydrate intake should be maintained to 45% to 60% of total energy.The guideline by the Department of Veterans Affairs and the Department of Defense recommends 14% to 45% of energy from carbohydrate and/or foods with lower glycemic index in patients with type 2 diabetes who do not use the Mediterranean diet.In the SIGN guideline, reducing dietary carbohydrate is recommended as one of the dietary options to lose weight and improve glycemic control in patients with type 2 diabetes.The results were limited by the various definitions and classifications of dietary interventions and the lack of direct comparisons between low-carbohydrate and standard diets.Due to the limitations, further research in the comparative effectiveness of low-carbohydrate diets in Canadian contexts may help reduce uncertainty in clinical decision making.