What does a post-meal glucose spike actually do to my arteries?

Each sharp glucose rise stresses the endothelium, the single-cell inner lining of your arteries, through a mechanism that is specific and measurable. Elevated postprandial glucose triggers reactive oxygen species production, which reduces nitric oxide bioavailability in endothelial cells, which impairs their ability to regulate vascular tone and resist inflammatory signals. The endothelium is your arteries' first line of defense against plaque formation. Every spike erodes that defense transiently.

This is not theoretical. Flow-mediated dilation, the standard measure of endothelial function, decreases measurably in healthy subjects after a glucose load that pushes them above 140 mg/dL. The effect is dose-dependent and cumulative. The man who spikes to 165 mg/dL after his morning oatmeal three hundred and sixty-five times a year is running a daily vascular stress load that his annual physical cannot see. (Ceriello et al., Circulation, 2008)

Cardiologist's calibrated position, Promising (2). The endothelial stress mechanism is well-established in short-term studies. The translation to long-term cardiovascular outcomes in non-diabetic men who never develop diabetes is suggestive but not yet established in prospective RCTs. The mechanism is real. The magnitude of contribution to lifetime cardiac risk, independent of all other factors, is not yet quantified.

What to do: A 10-minute walk after meals consistently blunts post-meal glucose peaks more effectively than most dietary interventions, by approximately 25–30%. Protein consumed before carbohydrates at the same meal reduces peak glucose by 15–20%. These are cheap, zero-risk interventions regardless of their cardiac benefit.

For the full picture, read The CGM on Your Arm Doesn't Know Your Arteries.