Written by Chrystal Moulton, Science Writer. Researchers observed a significant increase in systolic BP in the control group (p=0.023) and a significant decrease in systolic BP in the treatment group (p<0.05) compared to baseline.
Individuals who work under extreme temperatures are susceptible to elevated blood pressure [BP] due to increased metabolic rate, water loss, along with antioxidant and salt imbalance1-3. Studies have shown that vitamin C and flavonoids are beneficial in improving blood pressure [BP]4,5, however, conflicting evidence is found regarding vitamin C preventing elevated blood pressure [BP]6,7. Salt water is generally provided to steel workers prevent elevate blood pressure [BP] as a result of high heat exposure.(7) In China, ice lollypops and dried hawthorn, which needs to be soaked in water, is provided to steelworkers7. Hawthorn naturally contains flavonoids that prevent oxidative damage. However, soaking dried hawthorn is an inconvenient solution for steel workers that need a rapid response to oxidative stress endemic to their profession. In this study, researchers investigated the effect of vitamin C supplementation and hawthorn beverage on preventing elevated BP and oxidative stress in steelworkers.
This study was designed as a randomized control trial. Participants in this trial were from a single steel company in North China. Between 40-50 workers on 4 different shifts were invited to participate in the trial. Workers had to be 22-55years old and working for the company for more than 1 year to participate. Participants were excluded if they were already taking anti-hypertensive drugs or supplements, had any pre-existing chronic conditions, planned vacations during the trial, or were participating in other trials. Upon inclusion, participants were randomly assigned to the treatment group or placebo in a 1:1 ratio. Blinding was not possible for this trial. The treatment included 2 cans of hawthorn drink (279mg flavonoids) and 1 vitamin C tablet (130mg) daily for 40 days. The placebo was as slightly carbonated salted water. At the beginning, all participants were given salt water for 8 days before testing began. Once testing began, each worker was given his assigned protocol daily. Workers in the treatment group were told to take the vitamin C tablet before the shift and drink the hawthorn beverage during their breaks. To ensure compliance, workers in the treatment were required to post an image of the tablet packets and empty cans to an online document. Furthermore, guidance was also provided via text every shift and workers were required to report any side effects. BP and urine samples (after fasting) were collected at baseline and day 41. Blood pressure alone was also recorded on day 17. Anthropometric, demographic and dietary data was collected at baseline. The primary outcome of the study was a change in BP from baseline to day 41 and the secondary outcome was the net change in a urine metabolite concentration (8-iso-PGF2α). Linear mixed models were used to assess the effect of the treatment on blood pressure and urine 8-iso-PGF2α concentration.
132 eligible steel workers were randomly assigned to the placebo [n=68] or treatment group [n=64]. All participants completed the trial with no adverse events reported and 93.6% overall compliance. No significant differences were observed between the treatment and placebo groups at baseline. The average age across both groups was roughly 40years old. No significant difference was observed in total energy intake and dietary intake of antioxidants and vitamin C in both groups at baseline. Researchers observed a significant increase in systolic BP in the control group (p=0.023) and a significant decrease in systolic BP in the treatment group (p<0.05) compared to baseline. The mean difference in BP between treatment and control group from baseline to day 41 was -7.41mmHg (p<0.001) for systolic BP and -7.93mmHg (p<0.001) for diastolic BP. Researchers also found that workers in the treatment group with high systolic and diastolic BP experienced significant reductions in both at day 17 and day 41 compared to control (p<0.001). Workers in the treatment group also had a significant decrease in 8-iso-PGF2α urine concentration compared to placebo (p<0.001).
Overall, this study demonstrated that providing vitamin C tablets and hawthorn drink was more effective at preventing elevated blood pressure and lowering oxidative stress in steelworkers while working in extreme conditions than carbonated salt water. This finding has implications for other professions with workers in high heat environments. Additional studies will be needed to verify these results.
Source: Du, Wei, Shuhan Zhang, Jiajia Yang, and Hongmin Fan. “Effect of vitamin C and hawthorn beverage formula on blood pressure and oxidative stress in heat-exposed workers: a cluster-randomized controlled trial.” Asia Pacific Journal of Clinical Nutrition 33, no. 4 (2024).
Click here to read the full text study.
Posted October 24, 2024.
Chrystal Moulton BA, PMP, is a 2008 graduate of the University of Illinois at Chicago. She graduated with a bachelor’s in psychology with a focus on premedical studies and is a licensed project manager. She currently resides in Indianapolis, IN.
References:
- Meng-ying X, Zhao-yang W, Hong-min F, et al. Relationship Between Occupational High temperature exposure years and prevalence of hypertension: Based on restricted cubic spline model. Journal of Environmental and Occupational Medicine. 2016;33(11):1031-1036.
- Tang YM, Wang DG, Li J, et al. Relationships between micronutrient losses in sweat and blood pressure among heat-exposed steelworkers. Ind Health. Jun 10 2016;54(3):215-23. doi:10.2486/indhealth.2014-0225
- Kaldur T, Unt E, Ööpik V, et al. The acute effects of passive heat exposure on arterial stiffness, oxidative stress, and inflammation. Medicina (Kaunas). 2016;52(4):211-216. doi:10.1016/j.medici.2016.06.001
- Ponce O, Benassi R, Cesar T. Orange juice associated with a balanced diet mitigated risk factors of metabolic syndrome: A randomized controlled trial. Journal of Nutrition & Intermediary Metabolism. 2019;17:100101.
- Annuzzi G, Bozzetto L, Costabile G, et al. Diets naturally rich in polyphenols improve fasting and postprandial dyslipidemia and reduce oxidative stress: a randomized controlled trial. Am J Clin Nutr. Mar 2014;99(3):463-71. doi:10.3945/ajcn.113.073445
- Du W, Fan HM, Zhang YX, Jiang XH, Li Y. Effect of Flavonoids in Hawthorn and Vitamin C Prevents Hypertension in Rats Induced by Heat Exposure. Molecules. Jan 27 2022;27(3)doi:10.3390/molecules27030866
- Du W, Zhang S, Yang J, Fan H. Effect of vitamin C and hawthorn beverage formula on blood pressure and oxidative stress in heat-exposed workers: a cluster-randomized controlled trial. Asia Pac J Clin Nutr. Dec 2024;33(4):503-514. doi:10.6133/apjcn.202412_33(4).0005
