From the Guidelines
Increased protein intake generally does not directly cause increased A1c or fasting insulin levels in most people. Protein has minimal impact on blood glucose compared to carbohydrates, and moderate protein consumption is unlikely to worsen glycemic control 1. However, excessive protein intake, particularly animal protein consumed alongside high fat, can potentially contribute to insulin resistance over time in some individuals. This happens because when consumed in very large amounts, protein can be converted to glucose through gluconeogenesis, though this process is typically regulated and modest.
The quality of protein matters too - plant proteins generally have more favorable effects on insulin sensitivity than some animal proteins 1. For people with existing kidney disease, excessive protein intake requires caution as it may increase workload on the kidneys. If you're concerned about rising A1c or insulin levels, focus on overall dietary balance, emphasizing moderate protein intake (typically 0.8-1.2g per kg of body weight daily), quality carbohydrates, healthy fats, and regular physical activity rather than significantly restricting protein. Some key points to consider include:
- Individualized protein intake goals based on current eating patterns 1
- Successful management of type 2 diabetes with meal plans including slightly higher levels of protein (20–30%) 1
- Avoiding the use of carbohydrate sources high in protein to treat or prevent hypoglycemia due to the potential concurrent rise in endogenous insulin 1
- The benefits of higher plant protein intake and replacement of animal protein with plant protein, which is associated with lower risk of all-cause and cardiovascular mortality 1
From the Research
Increased Protein Intake and Its Effects on A1c and Fasting Insulin
- The relationship between high protein intake and its impact on A1c and fasting insulin levels is complex and has been studied in various contexts, including type 1 and type 2 diabetes 2, 3, 4, 5, 6.
- Some studies suggest that high protein intake can lead to increased insulin resistance and potentially higher A1c levels over time, particularly in the context of type 2 diabetes 2, 6.
- However, other research indicates that the effect of protein on blood glucose levels is minimal with adequate insulin, and the conversion of protein to glucose is slow, which may not significantly impact A1c or fasting insulin levels 5.
- A systematic review and meta-analysis found that a high-protein diet did not significantly improve glycemic control or blood pressure in type 2 diabetes patients but did lower insulin resistance and improve lipid profiles 6.
- In individuals with type 1 diabetes, protein ingestion can contribute to increased postprandial glucose levels due to the stimulation of glucagon secretion and increased endogenous glucose production 3.
- The study comparing high-protein and high-carbohydrate diets in patients with type 2 diabetes found that the high-carbohydrate group had decreased hemoglobin A1c and fasting plasma glucose, while the high-protein group had decreased systolic and diastolic blood pressures but no significant changes in A1c or fasting insulin 4.