February 2002
Q: I heard black tea is good for you. Is that true?
A: A study reported in July's Circulation: Journal of the American Heart Association, stated that black tea is rich in antioxidants, called flavonoids.
Flavonoids have been shown to prevent the oxidation of low-density lipoproteins (LDL), known as the "bad" cholesterol. Flavonoids are present in black tea, purple grape juice, red wine, and onions.
The study also found that the flavonoids in black tea improve the function of the vascular endothelium. The endothelium is the inner-most layer of cells found in all blood vessels. Substances found in the endothelium regulate the diameter of the blood vessel, making it dilate or constrict, depending on the blood flow needs of the body. In other words, during exercise, the vessels expand, as the need for blood is greater. In patients with atherosclerosis (cardiovascular disease), the endothelium does not function as it should (called endothelial dysfunction) which may contribute to heart attack and stroke. It is also important to note that black tea contains caffeine. Those with hypertension or irregular heart beats may be required to limit caffeine intake.
For more information:
- Caffeine: AHA recommendations *
- Duffy SJ, Keaney JF, Holbrook M, et.al. Short and Long-Term Black Tea Consumption Reverses Endothelial Dysfunction in Patients With Coronary Artery Disease. Circulation. 104: 151-156.
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