Effect of vitamin C and hawthorn beverage formula on blood pressure and oxidative stress in heat-exposed workers: a cluster-randomized controlled trial

Background and Objectives: There is no evidence on antioxidant-rich diets in preventing hypertension in heat- exposed workers. We aimed to evaluate the effects of formula supplemented with vitamin C (Vit C) and hawthorn beverage on reducing blood pressure (BP) and oxidative stress levels in heat-exposed workers. Methods and Study Design: In the 40-day cluster-randomized controlled trial, four heat-exposed shift-teams were enrolled and randomly assigned to the intervention and control groups. The intervention group was given one Vit C tablet (130 mg) and a 500 mL hawthorn beverage containing 278.7 mg flavonoids daily whereas the control group was given 500 mL of slightly salted water daily; both groups were provided education on a healthy diet. BP and creatinine-corrected urinary 8-isoprostane- prostaglandin F2 alpha (8-iso-PGF2 alpha/Cr)-iso- PGF2 alpha/Cr) concentrations were assessed at baseline, Day 17 (only BP) and Day 41, respectively. Results: Compared with the control group, the systolic BP (SBP), diastolic BP (DBP), and log10-transformed 8-iso- PGF2 alpha/Cr in the intervention group decreased by 7.41 mmHg, 7.93 mmHg and 0.232, respectively, from baseline to day 41 (all p <0.05). When comparing BP levels at baseline, DBP in the intervention group was reduced by 5.46 mmHg when compared to control (p<0.05) p <0.05) among participants with lower baseline BP; SBP and DBP experienced reductions of 9.74 and 9.22 mmHg among participants with higher baseline BP (both p <0.05). Conclusions: Supplementation of Vit C and flavonoids rich hawthorn beverage to heat-exposed workers prevented elevated BP caused by heat exposure which may be attributed to its oxidative stress inhibition effects.