When healthy young men were given insulin without changing their blood sugar, their body’s stress response system kicked in more — their heart beat faster and blood pressure rose, likely because insulin triggered their nerves to release more adrenaline.
Scientific Claim
In nonobese young men, insulin infusion at 2 mU/kg/min for 2 hours during euglycemic glucose clamp is associated with a 50% increase in plasma norepinephrine levels from a basal mean of 240 ± 34 pg/ml to 360 ± 41 pg/ml at 150 minutes, along with increases in pulse rate, pulse pressure, and pulse rate-systolic blood pressure product, indicating elevated sympathetic nervous system activity.
Original Statement
“In response to both insulin infusions, plasma NE rose progressively over the course of the study, increasing 50% with the 2-mU infusion (from mean basal value of 240 ± 34 pg/ml to 360 ± 41 at 150 min, P < 0.001 for changes over time by analysis of variance)... Associated with the elevations in plasma NE in the 2-mU insulin infusion were increases in pulse rate (P < 0.05), pulse pressure (P < 0.005), and pulse rate - systolic blood pressure product (P < 0.01).”
Evidence Quality Assessment
Claim Status
overstated
Study Design Support
Design cannot support claim
Appropriate Language Strength
association
Can only show association/correlation
Assessment Explanation
The abstract implies causation ('insulin infusion increases') but the study design lacks confirmed randomization or control for all confounders; thus, only association can be claimed. The verb 'increases' is too strong.
Evidence from Studies
Supporting (1)
Effect of Insulin and Glucose Infusions on Sympathetic Nervous System Activity in Normal Man
This study found that giving insulin to healthy young men, without changing their blood sugar, made their body’s stress system more active—shown by higher levels of a stress hormone and faster heart rate, which matches exactly what the claim says.