EAL

NNNS: Stevia (stevioside) (2010)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

In the present investigation the antihypertensive potential of oral crude stevioside obtained from the leaves of Stevia rebaudiana (Bertoni) Bertoni cultivated in northeastern Paraguay and southern Brazil was evaluated in a prospective, randomized, double-blind, placebo-controlled, single-center clinical trial. Moreover, the toxicological profile was expanded by assessing metabolic and hormonal parameters that were not evaluated by those studies (Chan et al., 2000; Hsieh et al., 2003).

Inclusion Criteria:

Untreated mild essential hypertension (pre-hypertension and stage 1), as defined in the seventh report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure on three consecutive measurements
Age more than 18 years.

Exclusion Criteria:

Pregnancy or childbearing potential
Hepatic and or renal dysfunction
Diabetes mellitus
Malignancy
Secondary hypertension of any etiology
Organ damage caused by hypertension
Cardiovascular diseases (stroke, myocardial infarction and angina pectoris)
Medication with an effect on blood pressure (BP).

Description of Study Protocol:

Recruitment

Workers at the experimental farm of the State University of Maringa (Brazil).

Design

Prospective, randomized, double-blind, placebo-controlled, single-center clinical trial.

Blinding Used

Double-blinded.

Intervention

Phase 0 (placebo phase): 18 patients; four-week single-blind phase; capsules containing talcum twice a day (before lunch and dinner)
Phases 1, 2 and 3 (active treatment): 24 weeks
- Fourteen patients from the placebo phases were randomly assigned to:
  - Placebo
  - Crude stevioside.
- Phase 1: Placebo vs. 3.75mg crude stevioside per kg per day for seven weeks
- Phase 2: Placebo vs. 7.5mg per kg per day for 11 weeks
- Phase 3: Placebo vs 15.0mg per kg per day for six weeks
The decision to use 3.75mg per kg per day as the initial dose of crude stevioside (phase 1) was based on a previous placebo-controlled double-blind study in which an absence of toxicity was observed in 25 subjects receiving stevioside capsules for 90 days. In addition, the decision to change the daily doses from 3.75mg per kg per day (phase 1) to 7.5mg per kg per day (phase 2) occurred only after a careful review of all indicatives of toxicity and adverse effects report chart. Accordingly, a similar procedure was adopted before phases 2 and 3.

Statistical Analysis

A computer-generated randomization program was employed to assign patients to receive either crude stevioside or placebo. This program ensured that both groups had similar baseline values.
Considering the limited final number of patients (six in each group) appropriated no parametrical statistical methods were employed, i.e., Mann-Whitney test for comparison between groups and Friedman-Wilcoxon test for comparison within group
The software Stattistica 6.0 was used for all statistical procedures. A 95% level of confidence (P<0.005) was accepted for all comparisons. Results were reported as mean ± standard deviation of mean (SD).

Data Collection Summary:

Timing of Measurements

Initial placebo phase was for four weeks
Phase 1 was for seven weeks
Phase 2 was for 11 weeks
Phase 3 was for six weeks
Measurements were taken at the end of each phase.

Dependent Variables

Blood pressure (BP): Measured after the subject had been sitting for at least 15 minutes and with the arm resting at heart level; BP was measured three times consecutively at five-minute intervals and the mean was used for analysis. None of the three consecutive BP readings could be more than 2mm Hg from the calculated average of the three readings. Additional readings had to be done until this was achieved.
Blood Analysis: Venous blood was collected after an overnight fasting at the end of each phase for:
- Hematology
- Serum ALT, AST, CPK, creatinine, urea, sodium, potassium, chloride, glucose, insulin, glycated hemoglobin, fructosamine, gamma-glutamyltransferase (GGT), total cholesterol, HDL-C, LDL-C, VLDL-C, triglycerides, free and total prostatic specific antigen, testosterone and estradiol
Urinalysis: Collected at the end of each phase for microscopic analysis of sediment, evaluation of glucose and of microalbuminuria. Another collection of 24 hours was done for sodium analysis.
BMI
Homeostasis model assessment (HOMA-IR) for insulin resistance = fasting insulin x fasting glucose/22.5.

Independent Variables

Placebo
Stevioside
Phase (but only for BP).

Control Variables

None listed
Patients were reminded to refrain from smoking or caffeine ingestion 30 minutes before measuring BP.

Description of Actual Data Sample:

Initial N

18 patients (unclear number of men and women; DBP: 80 to 99mm Hg and SBP: 120 to 159mm Hg).

Attrition (Final N)

During the placebo phase (Phase 0) three patients were excluded because of high values of BP (DBP higher than 110mm Hg or SBP higher than 160mm Hg) and one was excluded because an arrhythmia was detected
Fourteen patients (12 males, two females) entered Phase 1
Two patients were excluded from Phase 3, one from the placebo group (no compliance) and one from the stevioside group (epigastralgia)
Final N was six patients per group for a total of 12 (unclear number of men and women).

Age

At Phase 1, 43.3±5.64 years in placebo; 46.3±8.08 years in stevioside group.

Ethnicity

Unclear; workers at the experimental farm of the State University of Maringa (Maringa, Parana State, Brazil).

Anthropometrics

BMI ranged from 25.8 to 27.4.

Location

Brazil.

Summary of Results:

Combined Important Results from Tables 2 and 3

Parameter	Stevioside Before Treatment	Stevioside After Treatment	Placebo Before Treatment	Placebo After Treatment
HOMA-IR	2.7±1.7	1.2±0.6^a	2.4±1.0	1.2±1.1^a
Urine Na⁺ (mEq per 24 hours)	246.5±89.8	190.7±70.6	227.2±49.9	228.8±39.2
Glucose (mg per dL)	91.8±7.8	80.7±6.7^a	88.5±6.2	79.3±5.0^a
Insulin (mcg per L)	12.4±5.9	7.4±4.4^a	9.9±2.4	4.7±2.1
AST (U per L)	7.7±3.0	12.8±3.5	6.5±2.0	11.5±1.4
ALT (U per L)	5.7±1.8	9.2±2.6	6.0±1.3	9.5±3.6
Urea (mg per dL)	37.2±4.5	43.3±11.2	38.5±1.9	41.0±5.2

^aP<0.05 compared before and after treatment.

Other Findings

DBP decreased not only in patients who received crude stevioside but also in the placebo group from Phase 0 to the end of Phase 3 (P<0.05). DBP decreased from 94 to 84 (stevioside) and 82mm Hg (placebo).
Blood levels of testosterone, estradiol, free and total PSA were not modified by crude stevioside treatment
Blood levels of total cholesterol, LDL-C, VLDL-C, triglycerides, glucose, insulin were decreased at the end of phase 3 as were HOMA-IR and LDL-C/HDL-C ratio in both the placebo and stevioside groups. These results suggest a modification in lifestyle probably occurred during the study.
The authors stated that changes in hematological and urinalysis parameters were not observed
No major adverse clinical effects were observed during the study.

Author Conclusion:

The results suggest that oral crude stevioside is safe and supports the well-established tolerability during long term use as a sweetener, particularly in Brazil. However, in contrast to previous clinical trials, crude stevioside administered orally did not show an anti-hypertensive effect.
Limitation as cited by authors: Limited number of patients were used because the doses of crude stevioside overcame the acceptable daily intake (ADI), i.e., 5.5mg per kg per day.

Funding Source:

Government:

CNPq - grant number 400075/2002-0

Industry:

Steviafarma prepared the capsules containing standardized crude stevioside

Pharmaceutical/Dietary Supplement Company:

Reviewer Comments:

There are some serious limitations to this study.

Limited number of patients and unclear as to the final number of men and women in the study and in which group
Placebo contained talcum, which does not seem appropriate for a placebo treatment
Carryover effects from Phase 1 to 2 to 3 were not addressed
No justification for the duration of each Phase. Why were all Phases not of the same length?
Statistical analyses description is unclear as to which actual statistical tests were run
No statistical analyses for differences between Phases
Table 3 showed non-statistical increases in AST, ALT and urea in both the stevioside and placebo groups, which is of some concern even though the authors stated there were no differences and the oral crude stevioside was safe
Unclear if there is a conflict of interest.

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		???
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	???
	2.4.	Were the subjects/patients a representative sample of the relevant population?	???
3.	Were study groups comparable?		Yes
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	Yes
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	Yes
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	N/A
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	N/A
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		???
	4.1.	Were follow-up methods described and the same for all groups?	Yes
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	???
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	???
	4.4.	Were reasons for withdrawals similar across groups?	No
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		Yes
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	Yes
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	Yes
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	N/A
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	Yes
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	N/A
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	Yes
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	???
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		No
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	No
	8.2.	Were correct statistical tests used and assumptions of test not violated?	No
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	???
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	No
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	???
	8.6.	Was clinical significance as well as statistical significance reported?	???
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		???
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	???