Pre‐Exercise Galactose or Lactose Reduces Glycaemic Excursions During Exercise in Adults With Type 1 Diabetes: A Randomised, Double‐Blind, Crossover Trial

AIMS: To test whether pre-exercise galactose and lactose reduce glycaemic excursions during exercise compared with dextrose while maintaining protection against hypoglycaemia compared with placebo in adults with Type 1 diabetes METHODS: In a randomised, double-blind, 4-condition crossover trial, 14 adults with Type 1 diabetes completed four 60-min cycling sessions. Thirty minutes before exercise, participants consumed 20 g of dextrose, lactose, galactose, or placebo. The primary outcome was time to hypoglycaemia. Secondary outcomes included time in, below, and above range and glucose excursions. RESULTS: Seven hypoglycaemic events occurred (none after dextrose, two after lactose, one after galactose, and four after placebo; p = 0.42), with no difference in time to hypoglycaemia. Time in range was lower for dextrose (48% [95% CI 40-57]) compared with lactose (70% [95% CI 62-78]), galactose (71% [95% CI 63-79]), and placebo (86% [95% CI 80-91]) (all p ≤ 0.01). Time below range was lower for dextrose (0% [95% CI 0-3]), lactose (1% [95% CI 0-5]), and galactose (1% [95% CI 0-5]) compared with placebo (8% [95% CI 4-14]) (all p < 0.05). Time above range was higher for DEX (52% [95% CI 44-60]), LAC (29% [95% CI 21-37]), and GAL (28% [95% CI 21-36]) compared with PLA (7% [95% CI 3-12], all p < 0.01). CONCLUSIONS: Pre-exercise galactose and lactose provide more stable glycaemic responses than dextrose and reduce time below range compared with placebo. These findings support their use as effective pre-exercise nutritional strategies in individuals with Type 1 diabetes. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT05557227.