‘Sobolo’ lowers blood pressure, prevents prostate cancer from spreading – Study

Hibiscus Tea

For those who think that green and black tea are ideal for prostate health and lowering blood pressure, I have another good news for you as numerous credible studies have confirmed that hibiscus tea (sobolo) is superior to all these teas you have been drinking. Interestingly there have been extensive studies on hibiscus’ potential to lower blood pressure. What is also newsworthy is that studies have compared hibiscus tea to even pharmaceutical drugs for lowering blood pressure, and sobolo beats them in a clinical trial. Is this not interesting?

Let’s get started: Hibiscus tea, also known as sobolo, is a herbal tea that’s made by steeping parts of the hibiscus plant in boiling water. Ghana is gifted with the abundance of the hibiscus Sabdarrifa plant, and it is time we tapped the full potential of this plant. One of the most impressive and well-known benefits of hibiscus tea is that it may lower blood pressure. In this article, I examine the key ingredient used for the Ghanaian sobolo, hibiscus sabdariffa. Though other ingredients are added to make sobolo, this study is centred on hibiscus sabdariffa only.

Nutritional content

Jabeur et al. (2017) study examined the nutritional composition of hibiscus sabdariffa and found that sobolo contains the following:

Glucose (sugar), malic acid (organic acid), α-tocopherol (tocopherol), and linoleic acid (fatty acid) – as the major constituents. Also, 5-(Hydroxymethyl) furfural was the most abundant non-anthocyanin compound, while delphinidin-3-O-sambubioside was the major anthocyanin both in its hydroethanolic extract and infusion.

Scientific Studies, hibiscus sabdariffa

Sobolo leaves

Hibiscus tea and hypertension

Serban et al. (2015) review of five studies found that hibiscus tea decreased both systolic and diastolic blood pressure by an average of 7.58 mmHg and 3.53 mmHg, respectively. Another meta-analysis by  Corina et al (2015)found that drinking hibiscus tea significantly lowered both systolic and diastolic blood pressure.

Besides this, several studies have found that hibiscus tea may lower both systolic and diastolic blood pressure. In one retrospective study by Mckay et al. (2009), 65 people with high blood pressure were given hibiscus tea or a placebo. After six weeks, those who drank hibiscus tea had a significant decrease in systolic blood pressure, compared to the placebo.

One review in animal and human studies by Hopkins et al. (2013) also found evidence suggesting that extracts of Hibiscus tea are promising as a treatment for hypertension and cholesterol.

In a more recent retrospective study by  Jalalyazdi et al. (2019), where the case group received two standard cups of sour tea every morning for 1 month, they found that using H. sabdariffa as sour tea two times a day can be effective in managing blood pressure in stage one hypertension, along with lifestyle and dietary modification.

An observational study in Ghana suggests daily consumption of hibiscus tea, lowers blood pressure levels and may prove an effective component in cardiovascular health management (Obu, 2020).

Additionally, Obu’s (2020) thesis also showed one product, Dr. Nyarkotey Herbal Tea, which had hibiscus sabdariffa produced a dose-dependent reduction in the arterial blood pressure of the anesthetised cat comparable to acetylcholine. The depressor effects of acetylcholine and Dr. Nyarkotey Herbal Tea on the blood pressure of the anesthetised cat were inhibited by 72.3+5.21 percent and 55.6 + 6.82 percent respectively – suggestive of muscarinic mediation. The report states that as per the findings, “Dr. Nyarkotey Herbal Tea has hypotension effect, and hence, could be used in the management of hypertension”.

Another systematic review and meta-analysis by Boushehri et al. (2020) of randomised clinical trials also found that sour tea consumption could have a beneficial effect in controlling glycemic status and blood pressure among the adult population.

Another study by Amin et al. (2020) compared 10 different herbal medicines for hypertension and found hibiscus sabdariffa as a potential competent anti-hypertensive agent. Another scoping review by Etheridge and Derbyshire (2020) agrees strongest evidence exists that hibiscus tea supports cardiovascular disease, suggesting that drinking 2-3 cups daily (each ≈ 240-250 ml) may improve blood pressure and potentially serve as a preventative or adjunctive therapy against such conditions.

Hibiscus tea is the same as a pharmaceutical drug for hypertension  

Hibiscus tea has been compared to standard pharmaceutical drugs in lowering blood pressure and the results are fascinating. Let’s look at the studies:

The first study I chanced on was conducted by Herrera-Arellano et al. (2004). It went head-to-head with one of the most common pharmaceutical interventions for the treatment of hypertension, Captopril, an ACE inhibitor. In this study, individuals were either given daily hibiscus tea or 25 mg of Captopril twice per day. The result showed that the hibiscus tea and the Captopril had no significant difference in hypotensive effects, meaning that both the standard pharmaceutical drug and the hibiscus tea worked equally well in lowering the participants’ blood pressure.

The second study emerged from Nigeria by Nwachukwu et al. (2015), and discovered hibiscus tea to be more effective than hydrochlorothiazide, a common blood-pressure lowering medication, at decreasing blood pressure. The most significant finding was that hibiscus tea, unlike its study counterpart, hydrochlorothiazide, did not cause electrolyte imbalance. The study had this to say: “Hibiscus Tea (Natural medicine drug) was a more effective antihypertensive agent than HCTZ (conventional medicine drug) in mild to moderate hypertensive in Nigerians and did not cause electrolyte imbalance.

The third study conducted by Soleimani et al. (2015) also evaluate the effect of sour tea pills containing the herb’s extract versus Captopril on the treatment of hypertension. The authors had this to say: “According to the effect of sour tea pill on decreasing blood pressure, without giving priority over Captopril, sour tea pill containing the herb’s extract can be prescribed as an adjuvant therapy for lowering the prescribed dosage of Captopril”. No side effect was observed in the sour tea pill group in the study.

The fourth study conducted by Nurfaradilla et al. (2019) had this to say: “Hibiscus sabdariffa aqueous extract alone can reduce blood pressure. This extract appears could be used as a supplement with captopril but may not provide any additional benefit”.  What they meant was that hibiscus tea can be used as a stand-alone treatment for high blood pressure.

The fifth was another multi-centric pilot clinical study in Jordan by Al-Anbaki et al. (2019), thirty-eight participants with blood pressure (BP) above 140/90 mmHg were involved. Of the 38 participants, 29 finished the programme, 72 percent were taking anti-hypertensive medication due to uncontrolled hypertension and 28 percent were not. H. sabdariffa was generally well-tolerated: 38 percent of participants reached the target BP at the end of the study and 65 percent saw their systolic BP decrease by at least 10 mmHg. The study concluded that H. sabdariffa (karkade) is generally well-tolerated and seems to help treat uncontrolled hypertension, with or without medication.

The sixth emerged from an Egyptian study by Elkafrawy et al. (2020), which randomized 134 patients to receive Captopril 25 mg, low-dose NW Roselle, or high-dose NW Roselle twice daily for 8 weeks. The study concluded that Roselle had comparable anti-hypertensive efficacy and safety to Captopril in Egyptian patients with grade 1 essential hypertension.

The seventh is another similar randomised clinical trial by Bourqui et al. (2020) which assessed the clinical effectiveness of hibiscus sabdariffa in 219 hypertensive patients in Senegal, with Captopril as the control for six months. The study found hibiscus to be as effective as Captopril over the 6 months.

The eighth is another study by Kamyab et al. (2021), which also showed that hibiscus tea has the same effect as conventional medicines without serious side effects. The study further introduces sour tea as a suitable herbal medicine for high blood pressure.

The ninth study is a systematic review by Pattanittum et al. (2021). It found that the evidence is currently not strong enough compared to a placebo for controlling or lowering blood pressure in people with hypertension. This contradicts an earlier systematic review and meta-analysed by Boushehri et al. (2020), which suggests that sour tea consumption could have a beneficial effect in controlling glycemic status and blood pressure among the adult population.

Finally, the tenth study is a recent systematic review by Ellis et al. (2022) which proved otherwise and found that regular consumption of hibiscus could confer reduced cardiovascular disease risk. A similar study which makes it the eleventh, by Nurfaradilla et al. (2020), took a different perspective and indicated that co-administration of H. sabdariffa L. aqueous extract could change the pharmacokinetic profile of Captopril; therefore, its co-administration should be avoided. More studies are available for analysis.

Hibiscus tea, green and black tea, and blood pressure

Hibiscus Tea has also been compared head-to-head with other top natural medicine ingredients. For instance, Wahabi et al. (2010) systematic review found two studies that compared hibiscus sabdariffa to black tea and found that hibiscus had greater blood pressure reduction than black and green tea.

A similar study by Mozaffari-Khosravi et al. (2013) demonstrates that the therapeutic effectiveness of hibiscus tea and green tea drinking by the end of the intervention was 43.5 percent in the hibiscus tea group and 39.6 percent in the green tea group.


Packed with antioxidants

In one study in rats by Ajiboye et al. (2011), hibiscus extract increased the number of antioxidant enzymes, and reduced the harmful effects of free radicals by up to 92 percent. Another similar rat study by Ochani and Mello (2011) had similar findings, showing that parts of the hibiscus plant, such as the leaves, possess potent antioxidant properties.

Another clinical trial by Hadi et al. (2017) was conducted on 54 male soccer players. Participants were randomly assigned to three groups to receive: 450 mg/d green tea extract (GTE) in the first group, and 450 mg/d sour tea extract (STE) in the second group. The study found that those who took hibiscus tea (Cibolo) had increased antioxidant activity as compared to those who took green tea.

May help lower blood fat levels

In addition to lowering blood pressure, some studies have found that hibiscus tea may help lower blood fat levels, which is another risk factor for heart disease. For instance, in a retrospective study by Khosravi et al. (2009), 60 people with diabetes were given either hibiscus tea or black tea. After one month, those who drank hibiscus tea experienced increased ‘good’ HDL cholesterol and decreased total cholesterol, ‘bad’ LDL cholesterol and triglycerides.

Another study by Diaz et al. (2014) agrees that those with metabolic syndrome showed that taking 100mg of hibiscus extract daily was associated with decreased total cholesterol and increased ‘good’ HDL cholesterol. One previous study by Kuriyan et al. (2010) found no evidence that hibiscus sabdariffa leaf extract has a blood lipid-lowering effect.

Hibiscus promotes weight loss

Hibiscus tea also has zero calories if you don’t add any sweeteners. A human trial, (Chang et al. 2014) in Taiwan, used hibiscus extract for 12 weeks and all subjects saw a change. Results included a reduction in overall body weight, body fat, and hip-to-waist ratio. It turns out hibiscus contains a few anti-obesity properties. Hibiscus activates the AMPK compound which is found in many anti-obesity drugs. Once activated, it stimulates the breakdown of fats.

Another animal study by Alarcon-Aguilar et al. (2007) had similar findings, saying that giving obese mice hibiscus extract for 60 days led to a reduction in body weight.

Prevent cancers

One study by Zhou et al. (2016) found that hibiscus is high in polyphenols, compounds found to possess powerful anti-cancer properties. One test-tube study by Malacrida et al. (2016) found that hibiscus extract reduced cell growth and reduced the invasiveness of mouth and plasma cell cancers.

An earlier test-tube study by Chiu et al. (2015) found that hibiscus leaf extract averted human prostate cancer cells from spreading. Two test-tube studies (Lin et al. 2015; Lin et al. 2007) also found that hibiscus extract prevents stomach cancer cells by up to 52percent. Though human studies are needed, they provide a road map for hibiscus tea’s impact on prostate health.

Supports liver health

One clinical trial by Chang et al. (2014) in 19 overweight people found that taking hibiscus extract for 12 weeks improved liver steatosis. This condition happens as a result of the accumulation of fat in the liver, which can lead to liver failure. A study in hamsters by Huang et al. (2015) also found hibiscus extract supports the liver as it decreased markers of liver damage.

Another animal study by Ajiboye et al. (2011) also found that giving rats hibiscus extract increased the concentration of several drug-detoxifying enzymes in the liver by up to 65 percent.

Take note that these studies all evaluated the effects of hibiscus extract, instead of hibiscus tea.

Encourages menstruation [benefit & risk]

Hibiscus also affects oestrogen. This means that drinking hibiscus tea can induce menstruation. This is one of the examples of a hibiscus tea side effect that is beneficial to some but a risk to others. For some women, inducing menstruation is a good thing. If you have an irregular cycle it can help regulate your period. Or, even if you’re already regular, you can brew a cup of hibiscus tea to help with cramps.

Enhances breast milk & iron production

One study by Ali et al. (2020) found evidence that in Ghana some mothers used sobolo to support breast milk production. Another study by Kubuga et al. (2019) also found that consuming hibiscus sabdariffa leaf meals three times a week for 12 weeks during the dry/lean season in Northern Ghana improved the iron status of women of child-bearing age.

 Antibacterial and other properties

Hibiscus tea is almost like cranberry juice, with the same healing properties. Like cranberry juice, hibiscus works wonders for getting rid of and preventing urinary tract infections (UTIs). For instance, one test-tube study by Jung et al. (2013) found that hibiscus extract inhibited the activity of E. coli, a strain of bacteria that can cause symptoms like cramping, gas and diarrhea. Another test-tube study by Abdallah, M. (2016) found that hibiscus extract prevented eight strains of bacteria, and was as effective as some medications used to treat bacterial infections.

This study by Baatartsogt et al. (2016) wowed me. The study screened the anti-viral effects of 11 herbal tea extracts (hibiscus, black tea, tencha, rosehip tea, burdock tea, green tea, jasmine tea, ginger tea, lavender tea, rose tea, and oak tea) and found hibiscus the most prominent anti-viral natural drug. This means no virus can stand sobolo.

Hibiscus tea: How it works

Due to the impressive benefits of hibiscus tea, one review by Amos and Khiatah (2022) examined how hibiscus works. The study found that hibiscus sabdariffa’s anti-hypertensive potentials originate from the vasodilator activity, diuretic efficacy, functionality as an ACE inhibitor, adipocyte differentiation inhibitor, heart rate reduction ability, and anti-inflammatory mechanism. The cholesterol-lowering effect is dose-dependent and stems from the antioxidative effect and the activation of AMPK through phosphorylation and the inhibition of regulatory adipogenic transcription factors PPAR-γ, C/EBP-α, and SREBP-1c, which altogether results in lipid-lowering effect. As a diabetic lowering drug, hibiscus sabdariffa serves as anti-insulin resistance by inhibiting phosphorylation of IRS-1 with a similar effect to gliptins.

Sobolo: to drink it cold or hot?

Salem et al. (2022) brought a new perspective in a comparative study to examine the cold and hot aqueous extracts of hibiscus tea to determine its efficacy in lowering blood pressure. They found that both cold and hot extracts significantly lower blood pressure.

However, better results were displayed with the hot hibiscus tea, leading to a potential anti-hypertensive effect. They also concluded both cold and hot drinking present different health needs as different compounds from the hibiscus are released but hot hibiscus tea rather showed higher contents of specific ingredients in tea to which the superior anti-hypertensive and cardio protective activities could be related. What this also means is that you need to drink both cold and hot hibiscus tea at different intervals in case you want to get all the needed benefits.

Market size of hibiscus flower

The Grand View Research (2022) reports that the global hibiscus flower powder market size was estimated at US$113.3million in 2019 and is expected to expand at a compounded annual growth rate (CAGR) of 7.2 percent from 2020 to 2027, with a revenue forecast of US$197million. North America dominated the market for hibiscus flower powder and accounted for over 34.5 percent of global revenue share in 2019.

Warnings & precautions:

A review of clinical trials by Montalvo-González et al. (2022) suggests that hibiscus is generally safe for human consumption. This notwithstanding, hibiscus tea should be avoided in patients on blood thinning medications, pregnant and lactating mothers, and people with low blood pressure (hypotension) and low blood sugars (Hypoglycemia). This is demonstrated in one study by Ndu et al. (2011) which agrees that though hibiscus tea may be a safe and natural way to help lower blood pressure, it is not recommended for those taking hydrochlorothiazide, a type of diuretic used to treat high blood pressure, as it may interact with the drug. This means that hibiscus sabdariffa tea can be used as an alternative medication for high blood pressure management.

Take home

Several quality studies have found that hibiscus tea may lower both systolic and diastolic blood pressure. Amin et al. (2020) found Hibiscus sabdariffa as a potential competent anti-hypertensive agent as compared to another medicine. Another scoping review by Etheridge and Derbyshire (2020) used the phrase ‘strongest’ evidence in using hibiscus tea to lower blood pressure. Also, studies have found that there is no herbal tea in the market that can be compared to hibiscus tea in lowering blood pressure and one that has more antioxidants (Wahabi et .2010; Hadi et al. 2017).

Probably, if you are still wondering, then more than ten quality clinical trials (Nurfaradilla et al. 2019; Al-Anbaki et al. 2019; Elkafrawy et al. 2020; Bourqui et al. 2020; Kamyab et al.  2021; Pattanittum et al. 2021; Boushehri et al. 2020; Ellis et al. 2022; Nurfaradilla et al. 2020) have all compared hibiscus tea to pharmaceutical drugs in blood pressure lowering and hibiscus(sobolo) beats them.

What is also newsworthy is that the quality studies note that there is no need to take both hibiscus tea and pharmaceutical drugs to lower blood pressure at the same time. The reason is that hibiscus tea produces the same effect as a standard pharmaceutical drug for hypertension, and is safe.

Taking them together can cause an interaction so consult your physician. For the dosing, 3 concentrated cups a day per study is the ideal.

Finally, in case you are considering whether the cold sobolo or the hot one to drink. Salem et al. (2022) found that both cold and hot drinking present different health needs as different compounds from the hibiscus are released, but hot hibiscus tea rather showed higher contents of specific ingredients in tea to which the superior anti-hypertensive and cardio protective activities could be related; hence, you can decide to drink both to get different benefits. For diabetics, just in case you are considering the cold one, add no sugar. You can add healthy spices. I hope my review brings you joy on sobolo consumption! Thank you!


Prof. Nyarkotey has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations to justify his write-ups. My articles are for educational purposes and do not serve as medical advice for treatment. I aim to educate the public about evidence-based scientific Naturopathic Therapies.

The author is a Professor of Naturopathic Healthcare and President of Nyarkotey College of Holistic Medicine & Technology (NUCHMT)/African Naturopathic Foundation.  E-mail: [email protected]l.com.

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