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ORIGINAL ARTICLE
Year : 2014  |  Volume : 2  |  Issue : 2  |  Page : 109-114

Hibiscus sabdariffa L. drink improves postural stress-induced myocardial oxygen consumption changes in young adult men and women


1 Department of Physiology, College of Health Sciences, University of Ilorin, Ilorin, Nigeria
2 Department of Ophthalmology, University of Ilorin Teaching Hospital, Ilorin, Nigeria
3 Department of Clinical Pharmacy and Pharmacy Practice, Faculty of Pharmaceutical Sciences, University of Ilorin, Ilorin, Nigeria
4 Department of Physiology, College of Health Sciences, University of Ilorin, Ilorin, Nigeria; Department of Pharmacology, Kyungpook National University School of Medicine, Cardiovascular Research Institute, Daegu, Republic of Korea

Date of Web Publication17-Nov-2014

Correspondence Address:
Lawrence Aderemi Olatunji
Department of Physiology, College of Health Sciences, University of Ilorin, P.M.B. 1515, Ilorin 240001, Nigeria

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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2348-0149.144849

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  Abstract 

Aim: We hypothesized that Hibiscus sabdariffa drink would affect pressor and myocardial oxygen consumption (MVO 2 ) responses induced by postural stress in young healthy volunteers, and that the impact would be stronger in women than men. Materials and Methods: In a randomized, controlled, cross-over study, 25 young healthy male and 25 female subjects (18-27 years) drank nothing (control), water (500 ml; vehicle) or H. sabdariffa (1.4% w/v) 30 min before standing on three separate days of appointment. We measured supine and standing brachial blood pressure and heart rate (HR). MVO 2 was also estimated by the rate-pressure product (RPP). Results: Increases in systolic blood pressure (SBP) and RPP induced by standing when nothing or water was drunk was significantly larger (P < 0.05) than when H. sabdariffa drink was taken in both male and female subjects. However, H. sabdariffa drink had a stronger (P < 0.05) effect on SBP in women than in men, whereas the effect on RPP was stronger (P < 0.05) in men. Increases in diastolic blood pressure (DBP) and HR induced by standing when water was drunk were significantly larger than when H. sabdariffa drink was ingested in men. Conversely, increase in DBP induced by standing during water ingestion was not significantly attenuated by H. sabdariffa drink in women. Conclusion: The findings in the present study indicate H. sabdariffa drink impacts positively on the heart by reducing its demand for O 2 during postural stress, with a stronger effect in men relatively to women. This may be an important dietary intervention in preventing the development of cardiac dysfunctions among young individuals.

Keywords: Dietary intervention, Hibiscus sabdariffa, orthostatic tolerance, rate-pressure product


How to cite this article:
Usman TO, Akintoye O, Olatunji VA, Williams FE, Olatunji LA. Hibiscus sabdariffa L. drink improves postural stress-induced myocardial oxygen consumption changes in young adult men and women . Niger J Exp Clin Biosci 2014;2:109-14

How to cite this URL:
Usman TO, Akintoye O, Olatunji VA, Williams FE, Olatunji LA. Hibiscus sabdariffa L. drink improves postural stress-induced myocardial oxygen consumption changes in young adult men and women . Niger J Exp Clin Biosci [serial online] 2014 [cited 2022 Jan 23];2:109-14. Available from: https://www.njecbonline.org/text.asp?2014/2/2/109/144849


  Introduction Top


It has been reported that postural stress (active standing or head-up tilt) translocates 500-1000 ml of thoracic blood to the dependent vessels in the region below the diaphragm [1] especially, when ambulation is avoided. [2] Due to the gravitationally induced blood pooling, central blood volume and blood returning to the heart are reduced, resulting in reduced stroke volume and cardiac output. [3] Subsequently, this imposes postural stress by challenging blood pressure (BP) and cardiac functions. [4],[5] Despite the cardiovascular changes imposed by postural stress, individuals can stand upright as long as lower extremity fluid accumulation and decreased arterial pressure can be limited by cardiovascular reflexes and compensatory sympathetic-mediated peripheral vasoconstriction response as well as cardiovagal inhibition-mediated increase in heart rate (HR). [4],[6],[7] However, if the stress is too prolonged, the regulatory measures may fail, leading to postural stress-related hypotension, cerebral hypoperfusion and possibly syncope.

Myocardial oxygen consumption (MVO 2 ) is an important indicator of the workload on the heart, [8] and a good indicator of the response of the coronary circulation to increased myocardial oxygen demand. Major determinants of myocardial oxygen demand are left ventricular (LV) systolic pressure, radius, mass, contractility, and HR. MVO 2 is difficult to measure directly though, the rate-pressure product (RPP) is a reliable indicator employed in estimating MVO2. [9] Measuring changes in MVO 2 by RPP allows studies of various physiological, pathological and pharmacological events on the performance of the heart. [10] It is considered a strong determinant of cardiovascular risk since its increase precedes ischemic events. [11] Thus, RPP is used to measure the workload or oxygen demand of the heart and reflects hemodynamic stress. RPP is said to be raised in several cardiovascular risk factors such as increased body weight gain, sympathovagal imbalance [10],[11],[12],[13] and myocardial ischemia. [8],[14]

A wide range of natural dietary agents has been reported to possess the capacity to influence cardiovascular functions at rest and/or during stressful events in humans. Hibiscus sabdariffa Linnaeus (Malvaceae; H. sabdariffa) is a tropical plant that grows widely all over Central and West Africa, Southeast Asia and elsewhere. The aqueous extract of calyces of the flower is, usually, consumed as a cold beverage, hot drink or herbal medicinal agent worldwide. H. sabdariffa drink is rich in polyphenolic acids, flavonoids, and anthocyanins. Several studies have demonstrated that H. sabdariffa has beneficial effects including arterial BP-lowering effect. [15],[16],[17],[18],[19] It also ameliorates diabetic complications, [20],[21] possesses diuretic, [22] antioxidant [23],[24],[25],[26] activities and also antiatherosclerotic [27],[28],[29],[30],[31] effects. H. sabdariffa drink contains anthocyanins, which are believed to be active antihypertensive compounds, acting as angiotensin-converting enzyme (ACE) inhibitors. [17],[19]

Although the RPP relates strongly to important indices for cardiovascular morbidity and mortality, its implication during physiologically stressful events, particularly with dietary intervention in otherwise healthy young adults has not been documented. The present study was, therefore, undertaken to determine the possible beneficial effects of H. sabdariffa drink, a natural product consumed by a large population, on RPP in young adults. We also evaluate the gender-related effects since gender is an important factor when studying physiological systems.


  Materials and methods Top


Study subjects

Fifty (25 males, 25 females) apparently healthy nonobese young adults (age: 22.8 ± 0.4 vs. 20.5 ± 0.4 years; weight: 58.9 ± 1.7 vs. 53.0 ± 2.5 kg; height: 1.8 ± 0.01 vs. 1.6 ± 0.01 m; body mass index [BMI]: 18.5 ± 0.5 vs. 19.0 ± 0.9 kg/m 2 ; for males and females respectively) were recruited into the study. They were nonsmokers, normotensive, normoglycemic with no history of syncope, and not on any regular medications including contraceptive steroids. All subjects were recreationally active, but none was involved in a regular exercise regimen. All subjects were free of symptoms and/or history of cardiac, vascular, metabolic, neurological disease or diabetes. No woman was pregnant during the study, all had regular menstrual period of about 26-28 days. Subjects were screened with a careful history and physical examination. The study conformed to the ethical guidelines of the Declaration of Helsinki on the principles for research involving human subjects. Each subject was informed of the purpose and procedure used in the study before consent was obtained.

Hibiscus sabdariffa drink

Dried calyces of H. sabdariffa plant were purchased from a local market in Ilorin, Kwara State, Nigeria and were botanically authenticated by a botanist in the Department of Plant Biology of the University. The drink (1.4% weight/volume) was prepared as previously reported by McKay et al., [19] every morning prior to the study.

Experimental protocol

In a randomized, cross-over within-subject design, each volunteer underwent the study protocol 3 times under different conditions on separate days of appointment. The protocol was conducted between 7 am and 12 noon at room temperature (26°C ± 3°C) in order to avoid circadian autonomic variability. All volunteers were instructed to abstain from strenuous exercise, alcohol and caffeine-containing beverage for at least 24-h prior to laboratory testing. They had a 12-h overnight fast before the study and were asked to empty their urinary bladder before starting the study. [32] Baseline data were obtained during a 30 min period in the supine position after which the participants ingested nothing (control). They remained in the supine position for 30 min and then assumed a standing position for at least 5 min. On the other days of appointment, the volunteers were made to repeat the same protocol but ingested water (500 ml; vehicle) or H. sabdariffa drink (1.4% w/v) 30 min before standing. Cardiovascular responses induced by postural stress at 5 min were monitored by a blinded investigator.

Measurements

The recordings were taken at 10 min in the supine position and during standing after 5 min. The recordings were made in triplicate and average values were recorded. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) as well as HR were determined using an electro-sphygmomanometer (Seinex, SE-7000, Belfast, BT153HN, UK). RPP was estimated as a product of HR and SBP in supine and during postural stress. RPP was used as an estimate of the MVO 2 .

Statistical analysis

All data are given as means ± standard error of the mean of 25 male and 25 female subjects. Intra-individual and inter-individual differences were compared by paired and unpaired Student's t-test, respectively. P < 0.05 were considered as statistically significant and all tests were two-tailed. Statistical analyses were performed using SPSS (Version 17.0; SPSS® Chicago IL., USA).


  Results Top


Clinical characteristics

Both groups did not differ significantly in age, BMI, weight, and height. Preingestion means of SBP [Table 1], DBP [Table 2], HR [Table 3] and RPP [Table 4] during the different days of appointment were not significantly different in both the male and female groups.
Table 1: Effects of HS drink on SBP following 5 min standing in male and female subjects

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Table 2: Effects of HS drink on DBP following 5 min standing in male and female subjects

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Table 3: Effects of HS drink on HR following 5 min standing in male and female subjects

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Table 4: Effects of HS drink on RPP following 5 min standing in male and female subjects

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Effect of water and H. sabdariffa drink on cardiovascular responses to postural stress.

There was a significant (P < 0.05) increase in SBP in male and female subjects following 5 min of standing during control (male: 17.3% ± 1.5%; female: 15.6% ± 1.6%) and vehicle (male: 20.8% ± 2.1%; female: 18.2% ± 2.1%) usage [Figure 1]. However, this increase was significantly (P < 0.05) attenuated following H. sabdariffa drink ingestion, when compared to control and vehicle studies, with SBP rising by just 10.7% ± 2.0% in males and 4.7% ± 2.1% in females. This shows that H. sabdariffa drink had a much stronger effect on SBP in women than men.
Figure 1: Gender comparison of systolic blood pressure; *P < 0.05 versus water; #P < 0.05 versus male

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Diastolic blood pressure was significantly (P < 0.05) increased following 5 min of standing in both male and female subjects during control and vehicle usage [Figure 2]. However, ingestion of H. sabdariffa drink significantly (P < 0.05) attenuated the DBP in males, when compared with control and vehicle studies, but had no significant effect in females [Figure 2].
Figure 2: Gender comparison of diastolic blood pressure; *P < 0.05 versus water; #P < 0.05 versus male

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Water ingestion significantly attenuated the HR in female subjects [P < 0.05 vs. control; [Figure 3] during postural stress with a percentage change from baseline values of 6.1 ± 1.9 compared to 14.1 ± 1.7 that was observed during the control studies. However, H. sabdariffa drink had no significant effect on HR on the female subjects when compared to control values but significantly reversed the attenuated HR observed when water was ingested [6.1 ± 1.9 vs. 12.2 ± 2.8; P < 0.05; [Figure 3]. Conversely, ingestion of H. sabdariffa drink led to a significant attenuation of HR during postural stress in male subjects while water ingestion had no significant effect [Figure 3].
Figure 3: Gender comparison of heart rate; *P < 0.05 versus water; #P < 0.05 versus male

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Effect of water and H. sabdariffa drink on MVO 2 . The RPP was used as an indicator of MVO 2 . RPP was significantly (P < 0.05) increased when nothing or vehicle was ingested in both male (nothing: 33.5% ± 2.2%; vehicle: 47.9% ± 2.1%) and female (nothing: 26.6% ± 2.1%; vehicle: 30.6% ± 3.1%) subjects. However, ingestion of H. sabdariffa drink reduced the RPP, compared to when nothing or vehicle was ingested, with an increase of 27.3% ± 2.0% observed in males and 24.1% ± 2.2% in females. These values show that the effect of H. sabdariffa drink on RPP was larger in males than in females.


  Discussion Top


The results of this study demonstrate that H. sabdariffa drink attenuates increases in SBP and RPP induced by postural stress in both male and female volunteers. The results also indicate a stronger effect on SBP in women than in men, whereas the effect on RPP was stronger in men [Figure 4]. In addition, H. sabdariffa drink attenuated postural stress-induced increases in DBP and HR in men, but not in women. These findings reflect that the impact of H. sabdariffa on MVO 2 is associated with attenuated DBP and chronotropic responses in men but not in women during postural stress. This is the first reported vehicle/volume-controlled cross-over study, to the best of our knowledge, to examine the effect of H. sabdariffa drink on pressor and cardiac responses to physiological stress. Previous studies were conducted in older humans with high BP [17],[19],[33] and there was no report on cardiac effect, although there are some reported cardiac effects in hypertensive animal models. [16],[34] The observed attenuation of DBP and chronotropic responses may not be unconnected to the anthocyanins present in H. sabdariffa that has been shown in previous reports to be potent ACE inhibitors. [17],[19] Inhibitors of ACE prevent the conversion of angiotensin I to angiotensin II that is one of the most potent vasoconstrictors in the human body.
Figure 4: Gender comparison of rate-pressure product; *P < 0.05 versus water; #P < 0.05 versus male

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Rate-pressure product indirectly determines the MVO 2 and thus cardiovascular risk of subjects in question. Thus we can state that when nothing or water was ingested the hearts of male and female subjects consume comparable oxygen. However, when H. sabdariffa was ingested the hearts of male and female subjects consume less oxygen compared to when nothing or water was ingested.

Rate-pressure product has been documented to be correlated significantly and positively with LV walls thickness and stress, and negatively with LV end-diastolic dimensions of LV wall stress, in black-Africans. [35] It may suggest that H. sabdariffa drink could help prevent early development of enlarged left ventricle. Since the impact of H. sabdariffa drink on RPP is stronger in male than in female subjects, then it reflects that young adult men may have a better cardioprotection following ingestion of H. sabdariffa than age-matched women, particularly since young adult men are generally at a higher risk of developing cardiovascular dysfunctions than premenopausal women. The finding that H. sabdariffa drink may have cardioproctective effect possibly via blunted sympathetic-mediated chronotropic response is consistent with previous observations. [32]

The finding that the effect of H. sabdariffa drink on MVO 2 is not associated with attenuated DBP response in women during postural stress may not be untoward, rather may be advantageous in order to prevent young women of reproductive age that are susceptible to orthostatic intolerance.

Our results have also shown that reduction in RPP is largely due to attenuation of SBP in women, while for men the reduction in RPP is mainly due to attenuation of HR. However, the effect of H. sabdariffa drink on a long-term usage particularly with risks of developing CV dysfunctions should be attempted, because earlier studies among subjects with ischemic heart disease have found raised RPP to be associated with silent myocardial ischemia, and increased risk for acute myocardial ischemia and cardiovascular mortality. [36],[37]

Thus, the decrease in RPP that was mainly due to a decrease in HR rather than SBP during postural stress might be due to decreased sympathetic activity in men than in women. The decreased RPP during postural stress by H. sabdariffa drink suggests that individuals may not only have a reduced risk of cardiac dysfunctions but also have improved myocardial oxygen demand efficiency mechanisms, since previous studies have shown that cardiac dysfunction-prone conditions such as obesity are linked to disproportionate increases in the RPP change during physical stress. [38],[39],[40],[41]


  Conclusion Top


The findings in the present study indicate H. sabdariffa drink impacts positively on the heart by reducing its demand for O 2 during postural stress, with a stronger effect in men relatively to women. Because change in RPP to physiologically stressful events has been suggested as a simple, easy and reliable tool for early detection of cardiac dysfunction, usage of H. sabdariffa may therefore be an important dietary intervention in preventing the development of cardiac dysfunctions among young individuals.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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