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- Black Tea (Camellia sinensis)
- Cardiovascular Disease
| Date:
05-15-2012 | HC# 011236-448
|
Re: Black Tea Intake Improves Lipid Profile and Antioxidant Status
Bahorun
T, Luximon-Ramma A, Neergheen-Bhujun VS, et al. The effect of black tea on risk
factors of cardiovascular disease in a normal population. Prev Med. 2011; [epub ahead of print].
doi:10.1016/j.ypmed.2011.12.009.
Tea
(Camellia sinensis) has been reported
to promote good health. Black tea contains high levels of polyphenols, with the
major phenols being the flavan-3-ols, the flavonols, the flavones, and quinic
acid esters of gallic, coumaric, and caffeic acids. Although tea consumption
may help protect against cardiovascular diseases (a benefit attributed to its
polyphenols), "the intricate mechanisms of polyphenolic action still need
to be comprehensively understood," write the authors. They conducted a
randomized, controlled, parallel clinical trial to determine the effects of
black tea consumption on fasting serum glucose, total cholesterol (TC),
triglycerides (TGs), high-density lipoprotein (HDL) cholesterol, and
low-density lipoprotein (LDL) cholesterol, as well as the antioxidant status in
a normal population in the Republic of Mauritius.
To
be eligible, the participants had to be nonsmokers or former smokers between
ages 25 and 60 years, with an alcohol intake of fewer than 2 drinks daily, and
a cardiac ejection fraction (a measure of how well the heart is pumping)
greater than 40%. If postmenopausal, female participants could not be receiving
hormone replacement therapy (HRT). Of the 87 participants recruited for the
15-week trial, 77 (42 men and 35 women) completed it.
The
treatment group consumed 3 standard cups of 200 mL of black tea infusate daily
for 12 weeks without additives, followed by a 3-week washout period during
which they drank the same amount of hot water daily. The control group consumed
equal amounts of hot water for the same intervention period. Tea bags were
purchased from Mauritius Corson Tea Estate Co. Ltd (Curepipe, Mauritius). The
tea had high levels of gallic acid derivatives (50 ± 0.4 mg/L), flavan-3-ols
(42 ± 2 mg/L), flavonols (32 ± 1 mg/L), and theaflavins (89 ± 1 mg/L). The
Trolox equivalent antioxidant capacity (TEAC) and ferric reducing ability of
plasma (FRAP) values were 1055 ± 25 µmol/g and 825 ± 23 µmol/g of dry weight,
respectively.
Fasting
blood samples were drawn at baseline, at week 12, and at week 15. The mean
fasting blood glucose level at baseline was 134 ± 66 mg/dL for the men and 111
± 38 mg/dL for the women. At 12 weeks, those levels dropped significantly for
the men (30.2%) and for the women (14.8%) (P<0.001). Nonsignificant
decreases were observed in the control groups. The washout generally increased
the blood glucose level in the study groups. The authors note that the baseline
levels in both groups were higher than the international standard values and
that the Mauritian population is reported to have a 23.6% incidence of
diabetes. Examining the results of this trial, the authors conclude that "an
antihyperglycemic effect of black tea can therefore be anticipated."
Tea
consumption did not significantly influence TC levels in the men, but an
increase of 14% (P<0.05) was reported for the women. After the washout
period, very slight nonsignificant increases were reported in the tea group
compared with the levels at week 12. Very slight nonsignificant increases were
also noted in the control group.
The
baseline TG levels (166 ± 138 mg/dL for the men and 102 ± 65 mg/dL for the
women) were significantly reduced by 38.6% for the men and 28.6% for the women
(P<0.01) after 12 weeks of tea consumption. After the washout, TG levels increased
significantly by 25% in the men and 24% in the women (P<0.05). At week 12,
the control group reported nonsignificant decreases of TG levels in both men
and women, which were then followed by nonsignificant increases after the
washout period. "Relatively marked non-significant reductions were also
observed in the control groups thereby questioning the apparent inertness of
hot water," the authors state.
At
week 12, a slight nonsignificant reduction of LDL cholesterol was noted in the
men in the tea group, while a nonsignificant increase was seen among the women.
Washout increased the LDL levels nonsignificantly in both men and women. In the
hot water group, nonsignificant increases in LDL cholesterol were noted in both
men and women.
At
week 12, those in the tea consumption group had significantly increased HDL
cholesterol levels: 17% (P<0.05) in the men and 24% in the women
(P<0.05). After the washout period, highly significant increases of 15% in
the men and 29% in the women (P<0.001) were recorded. In the control group,
no significant changes were recorded for the men, while a highly significant
increase of 50% (P<0.001) was reported for the women's HDL cholesterol
levels; a significant increase (16.7%, P<0.05) continued during the washout
period.
The
mean LDL/HDL ratio (a predictor of atherosclerosis risk, with a ratio <3
considered normal) values for the men and women in the tea group were 2.65 ±
1.3 and 2.47 ± 1.5, respectively. After tea consumption, the tea-treated group
reported an overall significant decrease of 16.6% (P<0.05). The ratio values
decreased further during the washout period (nonsignificantly in the men and
significantly [P<0.05] in the women).
The
plasma total antioxidant activity was assessed by measuring TEAC and FRAP
values. A significant increase was seen in FRAP values in tea-treated men
(440%, P<0.05) and tea-treated women (386%, P<0.05) at week 12, followed
by a significant increase in the men during the washout period (P<0.01). Hot
water induced a significant increase of 482% (P<0.01) in the men and a
nonsignificant increase in the women at week 12.
TEAC
values were slightly reduced by tea intake in the men (P<0.05) and women
(P<0.05) at week 12. Following the washout period, the decrease continued
for the men, while the women recorded a very slight significant increase
(P<0.01). In the control group at week 12, a decrease in TEAC values was
observed for both men (P<0.01) and women (nonsignificant), followed by
nonsignificant increases after the washout.
As
seen in this study, the moderate intake of black tea improved the plasma levels
of some of the cardiovascular disease risk factors and total antioxidant
capacity. "Although the underlying biological mechanisms for these effects
and the exact role of phenolics warrant an extensive study, tea may provide an
important source of dietary antioxidants in many individuals," conclude
the authors.
—Shari Henson
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