It's become part of popular nutrition advice that people should avoid foods that "spike" their blood sugar, with the belief that sharp rises and drops in blood sugar over time cause insulin insensitivity, pancreatic beta cell fatigue, or other metabolic harm. I mostly see this in discussions of the glycemic index or "slow carb" diets. A few examples: Glycemic Index foundation, Medical News Today, Healthline, United Healthcare
I understand that chronically elevated blood sugar can cause these problems, but what is the evidence that temporary high blood sugar is harmful in this way? I would be interested in long-term glucose monitoring studies, short-term biomarker studies, or even theoretical arguments.
To clarify some things:
- Some people find that blood sugar spikes are followed by negative effects on mood, satiety, or cognition. I'm asking whether blood sugar spikes contribute to metabolic issues separately from that (ie, not because the person responds to a spike by eating sugary foods that lead to other health issues)
- Extreme high levels of blood sugar can be unhealthy in other ways; I'm asking about sudden changes within a normal range (say, a rapid postprandial rise from 90 to 140, followed by a rapid drop), in people who do not have diabetes
- I'm familiar with reasons for believing that prolonged high blood sugar leads to insulin insensitivity; I'm specifically asking about sudden, brief elevations.
- High blood sugar variability can be caused by poor insulin sensitivity; I'm asking about the opposite direction