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Effects on blood pressure of drinking green and black tea.

Abstract

BACKGROUND

The flavonoid components of tea have been associated in epidemiological studies with a decreased risk of cardiovascular disease. Flavonoids have been shown to have antioxidant and vasodilator effects in vitro; we therefore postulated that drinking green or black tea attenuates the well-characterized acute pressor response to caffeine and lowers blood pressure during regular consumption.

OBJECTIVE

To determine whether green and black tea can attenuate the transient pressor effect of caffeine, or lower blood pressure during regular consumption.

METHODS

In the first study, the acute effects of four hot drinks - green tea and black tea (at a dose equivalent to four standard cups), water matched to the teas for caffeine content ('caffeine') and water - were assessed in 20 normotensive men using a Latin-Square designed study. Clinic blood pressure was measured before and 30 and 60 min after each drink had been ingested. In the second study, the effects on blood pressure of regular green and black tea ingestion were examined in 13 subjects with high-normal systolic blood pressure and mild systolic hypertension (systolic blood pressure in the range 130-150 mmHg) using a three-period crossover study. Five cups per day of green tea, black tea and caffeine (in hot water and matched to the teas) were consumed for 7 days each, in random order. Twenty-four hour ambulatory blood pressure was measured at the end of each seven-day intervention. Results are presented as means and 95% confidence intervals (CI).

RESULTS

An acute pressor response to caffeine was observed. Relative to caffeine, there were further acute increases in systolic and diastolic blood pressure at 30 min among those drinking green tea [5.5 mmHg (95%CI -1.4 to 12.4) and 3.1 mmHg (95%CI -0.1 to 6.3), respectively] and black tea [10.7 mmHg (95%CI 4.0 to 17.4) and 5.1 mmHg (95%CI 1.8 to 8.4), respectively]. The changes in blood pressure at 60 min were not significant The effect on 24-h ambulatory systolic and diastolic blood pressure of regular drinking of green tea [increases of 1.7 mmHg (95%CI -1.6 to 5.0) and 0.9 mmHg (95%CI -1.3 to 3.1), respectively] or black tea [increase of 0.7 mmHg (95%CI -2.6 to 4.0) and decrease of 0.7 mmHg (95%CI -2.9 to 1.5), respectively] was not significant relative to caffeine.

CONCLUSIONS

Contrary to our initial hypothesis, tea ingestion caused larger acute increases in blood pressure than caffeine alone. However, any acute effects of tea on blood pressure did not translate into significant alterations in ambulatory blood pressure during regular tea consumption.

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  • Authors+Show Affiliations

    ,

    University of Western Australia Department of Medicine and the Western Australian Heart Research Institute, Royal Perth Hospital, Australia. jonathan@cyllene.uwa.edu.au

    , , ,

    Source

    Journal of hypertension 17:4 1999 Apr pg 457-63

    MeSH

    Adult
    Aged
    Blood Pressure
    Caffeine
    Cross-Over Studies
    Female
    Flavonoids
    Humans
    Male
    Middle Aged
    Plant Extracts
    Tea

    Pub Type(s)

    Clinical Trial
    Journal Article
    Randomized Controlled Trial
    Research Support, Non-U.S. Gov't

    Language

    eng

    PubMed ID

    10404946

    Citation

    Hodgson, J M., et al. "Effects On Blood Pressure of Drinking Green and Black Tea." Journal of Hypertension, vol. 17, no. 4, 1999, pp. 457-63.
    Hodgson JM, Puddey IB, Burke V, et al. Effects on blood pressure of drinking green and black tea. J Hypertens. 1999;17(4):457-63.
    Hodgson, J. M., Puddey, I. B., Burke, V., Beilin, L. J., & Jordan, N. (1999). Effects on blood pressure of drinking green and black tea. Journal of Hypertension, 17(4), pp. 457-63.
    Hodgson JM, et al. Effects On Blood Pressure of Drinking Green and Black Tea. J Hypertens. 1999;17(4):457-63. PubMed PMID: 10404946.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Effects on blood pressure of drinking green and black tea. AU - Hodgson,J M, AU - Puddey,I B, AU - Burke,V, AU - Beilin,L J, AU - Jordan,N, PY - 1999/7/15/pubmed PY - 1999/7/15/medline PY - 1999/7/15/entrez SP - 457 EP - 63 JF - Journal of hypertension JO - J. Hypertens. VL - 17 IS - 4 N2 - BACKGROUND: The flavonoid components of tea have been associated in epidemiological studies with a decreased risk of cardiovascular disease. Flavonoids have been shown to have antioxidant and vasodilator effects in vitro; we therefore postulated that drinking green or black tea attenuates the well-characterized acute pressor response to caffeine and lowers blood pressure during regular consumption. OBJECTIVE: To determine whether green and black tea can attenuate the transient pressor effect of caffeine, or lower blood pressure during regular consumption. METHODS: In the first study, the acute effects of four hot drinks - green tea and black tea (at a dose equivalent to four standard cups), water matched to the teas for caffeine content ('caffeine') and water - were assessed in 20 normotensive men using a Latin-Square designed study. Clinic blood pressure was measured before and 30 and 60 min after each drink had been ingested. In the second study, the effects on blood pressure of regular green and black tea ingestion were examined in 13 subjects with high-normal systolic blood pressure and mild systolic hypertension (systolic blood pressure in the range 130-150 mmHg) using a three-period crossover study. Five cups per day of green tea, black tea and caffeine (in hot water and matched to the teas) were consumed for 7 days each, in random order. Twenty-four hour ambulatory blood pressure was measured at the end of each seven-day intervention. Results are presented as means and 95% confidence intervals (CI). RESULTS: An acute pressor response to caffeine was observed. Relative to caffeine, there were further acute increases in systolic and diastolic blood pressure at 30 min among those drinking green tea [5.5 mmHg (95%CI -1.4 to 12.4) and 3.1 mmHg (95%CI -0.1 to 6.3), respectively] and black tea [10.7 mmHg (95%CI 4.0 to 17.4) and 5.1 mmHg (95%CI 1.8 to 8.4), respectively]. The changes in blood pressure at 60 min were not significant The effect on 24-h ambulatory systolic and diastolic blood pressure of regular drinking of green tea [increases of 1.7 mmHg (95%CI -1.6 to 5.0) and 0.9 mmHg (95%CI -1.3 to 3.1), respectively] or black tea [increase of 0.7 mmHg (95%CI -2.6 to 4.0) and decrease of 0.7 mmHg (95%CI -2.9 to 1.5), respectively] was not significant relative to caffeine. CONCLUSIONS: Contrary to our initial hypothesis, tea ingestion caused larger acute increases in blood pressure than caffeine alone. However, any acute effects of tea on blood pressure did not translate into significant alterations in ambulatory blood pressure during regular tea consumption. SN - 0263-6352 UR - https://www.unboundmedicine.com/medline/citation/10404946/Effects_on_blood_pressure_of_drinking_green_and_black_tea_ L2 - http://Insights.ovid.com/pubmed?pmid=10404946 DB - PRIME DP - Unbound Medicine ER -