608-P: Carbohydrate Intake, Glycemic Control, and Cardiometabolic Risk Factors in Type 1 Diabetes—A Systematic Review and Meta-regression

Summary: Carbs and Type 1 Diabetes—What This Review Found

This systematic review and meta‑regression looked at how much carbohydrate people with type 1 diabetes eat and how that relates to blood sugar control, insulin needs, and blood lipids. It analyzed 101 studies with 45,972 participants across carbohydrate intakes from very‑low to high.

Key Findings

• Lower carbohydrate intake was linked to better blood sugar control (HbA1c) and lower insulin needs—up to an average intake of 225 g/day. Below this point, every additional 50 g of carbs/day was associated with higher HbA1c (+0.52%) and higher insulin dose (+0.12 IU/kg/day).
• Above 225 g/day, more carbs weren’t tied to higher HbA1c or insulin dose, but were linked to more glucose variability (+11.6 mg/dL standard deviation per 50 g), meaning blood sugars swung more.
• No link was found between carb intake and LDL‑C, HDL‑C, or triglycerides.
• The ADA HbA1c target (<7%) was achieved in: - 10% of high‑carb studies (≥45% calories), - 24% of moderate (26–44%), - 78% of low (10–25%), - 100% of very‑low (<10%) carb studies.
• The authors conclude: reducing dietary carbs is associated with improved glycemic control without changes in blood lipids, suggesting carb reduction may help lower cardiometabolic risk in T1D. These are observational findings.

Practical Relevance for People with Type 1 Diabetes

• If your HbA1c is above target, reducing daily carbs may be associated with lower HbA1c and less insulin needed.
• Very‑low and low‑carb approaches, in the studies reviewed, were more likely to meet <7% HbA1c, without observed changes in common lipid markers.
• High‑carb intakes were linked to greater glucose variability, which can make day‑to‑day management harder.
• These results are observational—they point to a pattern, not proof of cause. Individual responses vary, and insulin management strategies differ.