Green Tea Attenuates Pressure Reduction Induced by a Session of Physical Exercise
Condition: Hypertension
MeSH terms: Hypertension
Study type: Interventional

Summary: 
      The objective is to investigate whether the ingestion of green tea prior to physical exercise
      improvement post-exercise hypotension (PEH). Double-blind, randomized, placebo study. Fifteen
      hypertensive (53±4.5 years) performed three procedures: green tea+exercise (GT+Ex),
      placebo+exercise (PL+Ex), green tea without exercise (GT). Thirty minutes after ingesting 2g
      of green tea or placebo, they performed treadmill walking (60 minutes), 60 to 85% of maximum
      heart rate intensity in procedures with exercises. BP was measured at rest and at every 10
      minutes after exercise (60 minutes). Blood samples were taken before the ingestion of green
      tea or placebo and immediately after exercise to determine Malondialdehyde (MDA) and Nitrite
      (NO) dosages. Reduction of systolic BP compared with the rest, during PL+Ex recovery
      procedure.
    

Detailed description: 
      Subjects of study: Double- blind study, randomized and placebo, conduced with fifteen both
      sexes hypertensive individuals, physically active and practitioners of exercises for at least
      3 months prior to trials. All patients were users of anti- hypertensive medication except
      beta- blockers and maintained medication throughout study period. They were demanded not to
      be diabetic and women not menopaused. The research was approved by the Ethics Committee on
      Research with Human Beings of the Health Sciences Centre at the Federal University of
      Paraiba- CEP/ CCS, under the protocol 0120/13. Individuals were required to sign The Free and
      Clarified Consent Term (FCCT), according to resolution 196/96 of National Health Council.

      Study Designs: subjects performed three experimental procedures, two practicing aerobic
      exercises and one without physical exercises. The sessions with exercises were conducted
      under previous administration of a green tea dosage or placebo (GT+Ex or PL+Ex), ingested 30
      minutes before the start of exercises protocol. In the session without exercises (GT) they
      ingested green tea and remained sit during the same period destined to the exercises. Heart
      Rate Measurement were registered at rest (RHR) and in every ten minutes during physical
      exercise protocol. BP measurements were taken before (at rest), immediately after exercise
      and in every ten minutes during a recovery period of 60 minutes after the end of exercise
      protocol, or in the period they remained sit. Blood samples were collected prior and
      immediately after exercise or period without exercise for analysis of plasmatic concentration
      of anti and pro- oxidant agents (nitrite- NO and Malondialdehyde- MDA).

      Instruments and Procedures:Physical Exercises: After the purposes of the research were
      clarified to the individuals, they were invited to proceed to the laboratory in order for
      exercise sessions performance. The groups were submitted to three sessions, two of those on
      treadmill aerobic exercise during 60 minutes. Furthermore, it was established that the
      individuals should practice exercises scoring between 11 and 14 in Borg and Noble's
      Subjective Perceived Exertion Scale. They were requested to hold the intensity of physical
      exercises from 60% to 85% of HRmax (maximum Heart Rate), monitored during sessions with a
      Polar frequency meter model RS800CX (Polar ElectroOy, Kempele, Finland).

      Supplementation of Green Tea or Placebo: Green tea and placebo capsules were produced in a
      compounding laboratory. The investigators used 2g of green tea dried leaves and discovered an
      improvement in oxidative stress. The group with green tea consumption ingested capsules with
      2g of concentrated powder, approximately 1960mg in polyphenols (636mg of epigallocatechin
      gallate) and 20mg of caffeine; placebo group consumed capsules containing 2g of cornstarch
      powder, all swallowed with water. Capsules were administered to patients after a skilled
      professional collected blood samples. Researchers conducted supplementation of substances
      after pre- exercise blood collection and sessions initiated only 30 minutes after the
      ingestion of capsules, which is the time required by the body to absorb nutrients.

      Blood Pressure Measurement: Individuals had their BPs checked previously, immediately after
      the end of the exercise and during 60 minutes post- exercise. BP at rest was verified after
      the subjects remained sit for 10 minutes. By the end of the walking session, BP was checked
      with sitting subjects. During recovery, BP was verified in every 10 minutes during all 60
      minutes of walking session. The protocol adopted was the one proposed by the Brazilian
      Society of Cardiology and the Brazilian Society of Hypertension.

      Blood Collection Protocol: Performed prior and immediately after exercise. Ten milliliters
      (ml) of blood were collected from the antecubital vein, of which five ml were placed in test
      tubes containing EDTA and carefully homogenized by inversion. The other five ml were placed
      in tubes without any anticoagulant. Then they were centrifuged at 1500 rpm for 20 minutes.
      Plasma was isolated, placed in ependorf tubes and refrigerated in 20 ºC until analysis.

      Evaluation of oxidative stress (MDA): Oxidizing activity was quantified through
      thiobarbituric acid reaction with the products from hydroperoxides decomposition. Therefore,
      250 µl of sample was added to KCl and incubated in water bath maintained at 37° C for 60
      minutes. Then mixture was precipitated with 35% AA perchloric and centrifuged at 14000 rpm
      and 4°C for 10 minutes. Supernatant was transferred to new ependorfs, adding 400 µl of 0.6%
      thiobarbituric acid and incubated at 95-100° C for 30 min. After cooling, material was read
      by spectrophotometer at a wavelength of 532nm.

      Nitrite Dosage The method was based on the Griess reagent usage. Reagent was prepared
      utilizing equal parts of 5% phosphoric acid, 0.1% N-1-naphthalenediamine (NEED), 1%
      sulphanilamide, 5% in phosphoric acid and distilled water. To accomplish the test, 100 µl of
      10% homogenate supernatant made with potassium phosphate buffer was added to 100µl Griess
      reagent. Regarding the white one, 100 µl reagent was added to 100 µl of buffer and series of
      dilutions were conducted to obtain standard curve (100, 50, 25 12.5, 6.25, 3.12, 1.56 µm) of
      nitrite. The entire test was executed in a 96 well- plate template with reader at an
      absorbance range of 560 nm.

      Data Analysis Process: Initially, all data were tested concerned its normality and
      variability in standard error. Subsequently, one-way ANOVA tests were applied in order to
      compare basal conditions within three days of proceedings. Instat 3.0 software
      (GraphPAdInstat, San Diego, CA, USA) was utilized during analysis.
    

Intervention name(s): GT+Ex; PL+Ex; Green Tea
Intervention type(s): Dietary Supplement; Dietary Supplement; Dietary Supplement
Intervention description(s): In this session the volunteers ingested capsules with 2g of powder green tea before exercise; In this session the volunteers ingested capsules with 2g of placebo before exercise; In this investigation the volunteers ingested capsules with 2g of powder green tea before the rest similar to the exercise time
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)