A clinical trial comparing the effects of cinnamon, cardamom, saffron and ginger decocted with black tea on endothelial function and blood pressure in type II diabetes.
In this article, we discuss the “Effect of cinnamon, cardamom, saffron and ginger consumption on blood pressure and a marker of endothelial function in patients with type 2 diabetes mellitus: A randomized controlled clinical trial“ (1).
Aim of study
To compare the effects of cinnamon, cardamom, saffron and ginger consumption on markers of endothelial function and blood pressure (BP) in diabetic patients.
Study method
Parallel, randomized, single-blind placebo-controlled clinical trial.
Male and female patients with diabetes were selected if they were aged ≥ 30 years, had been diagnosed with type 2 diabetes mellitus (T2DM), were overweight [body mass index (BMI) ≥ 25 kg/m2] and were not on insulin therapy. Patients were randomised to one of five groups outlined below.
Measures included: endothelial function via serum sICAM-1 (an endothelial adhesion molecule involved in inflammation), blood pressure and anthropometrics — weight and waist circumference.
The study was carried out in Iran.
Herbal preparation
All patients consumed three glasses of black tea a day as a vehicle. Groups included control (no herbs), 3 g cinnamon, 3 g cardamom, 1 g saffron or 3 g ginger. The herbs were raw, dried powders mixed in the tea. The teas with herbs were brewed in a traditional manner by boiling in a kettle for 10 minutes. Teas were consumed at three separate times throughout the day. The herbs were consumed for eight weeks.
Sample size
In total, n=204: cinnamon (n=40), cardamom (n=42), saffron (n=42), ginger (n=41), control (n=39). There was a significant difference in age and weight across some of the groups despite randomisation, with saffron being both the oldest and heaviest. The statistical tests accounted for this.
Results of study
There were no significant differences between the herbal groups with regards to serum sICAM-1 levels, BP or anthropometric measures compared to the control group.
For individual herbs, saffron and ginger consumption reduced sICAM-1 levels from the baseline to the end of the study (although actual values are marginal). Ginger also significantly reduced systolic blood pressure (again values were marginal). Other data presented was not significant.
Discussion
After eight weeks of consuming black tea boiled for 10 minutes with herbs, the patients with diabetes in the study showed no significant differences between the four individual herbs consumed and the control group for any measures. Herbs were consumed in weights comparable with other studies. The patients kept diet and activity diaries, and their habits did not alter during the course of the study.
Looking at individual herbs, saffron and ginger significantly reduced sICAM-1 concentrations, and ginger intake reduced systolic blood pressure over the study period. Although the results were significant, the value improvements were only marginal.
In diabetes, endothelial dysfunction may contribute to the vascular complications often seen, and there can be loss of vasodilation that may result from persistent higher blood glucose, oxidative stress and inflammation. Therefore, reductions in slCAM-1 are meaningful in diabetes, although other tests of endothelial function and blood flow would confirm these findings.
The study took place in Iran where the tea was brewed traditionally. It might be that the boiling of the herbs for 10 minutes (rather than steeping and making a herbal tea) damaged some of the constituents, such as essential oils.
Also, it might be that the high levels of black tea consumption in this population might be already providing protective effects on their diabetic biomarkers. There have been several meta-analyses on the potential antidiabetic actions of black tea (and other herbal teas), for example, one summarising 19 clinical studies showing that black tea regulated glycaemic control, lipid profiles and blood pressure, although not affecting total cholesterol or waist circumference (2).
A 2024 article presents UK Biobank data and an analysis of 212,146 people over time from being healthy to developing diabetes and then diabetic complications. The study looked for associations between tea and coffee intake and metabolomic signatures during the progression of diabetes. For both tea and coffee, there was an inverse association with metabolomic signatures at five disease transition points. This study highlights the benefits of tea (and coffee) in reducing the risk of occurrence and then progression of type 2 diabetes (3).
Conclusion
To recap on the herb study, the consumption of cinnamon, cardamom, saffron or ginger did not significantly alter endothelial function, blood pressure or other risk factors for cardiovascular disease seen in diabetes.
Further research comparing a group of non-tea drinkers consuming herbs as powders taken in un-boiled water would offer an interesting comparative insight.
References
- Azimi, P., Ghiasvand, R., Feizi, A., Hosseinzadeh, J., Bahreynian, M., Hariri, M., & Khosravi-Boroujeni, H. (2016). Effect of cinnamon, cardamom, saffron and ginger consumption on blood pressure and a marker of endothelial function in patients with type 2 diabetes mellitus: A randomized controlled clinical trial. Blood pressure, 25(3), 133–140. https://www.tandfonline.com/doi/full/10.3109/08037051.2015.1111020#abstract
- Wang, P., Ma, X. M., Geng, K., Jiang, Z. Z., Yan, P. Y., & Xu, Y. (2022). Effects of Camellia tea and herbal tea on cardiometabolic risk in patients with type 2 diabetes mellitus: a systematic review and meta‐analysis of randomized controlled trials. Phytotherapy Research, 36(11), 4051–4062.
- Zheng, G., Ran, S., Zhang, J., Qian, Z., Tian, F., Shi, H., … & Lin, H. (2024). Characterizing metabolomic signatures related to coffee and tea consumption and their association with incidence and dynamic progression of type 2 diabetes: A multi-state analysis. American Journal of Epidemiology. kwae400. https://academic.oup.com/aje/advance-article-abstract/doi/10.1093/aje/kwae400/7823754
