High blood pressure, also known as hypertension, is a common health complaint that is estimated to affect almost one in three adults in the US and UK. Although severity can vary, a medical diagnosis for hypertension is often given when blood pressure readings consistently exceed 140 over 90.
The leading methods to reduce blood pressure are through the use of medication, lifestyle changes (diet, exercise) and taking dietary supplements or herbs. Here we will take a look at the herbs which can be used to treat this condition.
Whilst many herbs purport to reduce blood pressure, we are interested in only those which have been shown to work in clinical trials on human subjects and which resulted in a statistically significant reduction in blood pressure. The more trials performed on a particular herb, the more reliable the evidence relating to any health benefits. Let’s take a look.
The first on our list is ‘Hibiscus Sabdariffa’ or ‘Roselle’ – a flowering plant which is one of over 250 different species found growing around the world. This species of hibiscus is the one most commonly used for medical purposes and is best know as a sour tasting, vivid red tea infusion.
What is interesting about this plant is that it has been shown to significantly reduce blood pressure in a number of human studies on both hypertensive and prehypertensive adults. All but one of the studies used hibiscus tea which is made from the deep coloured magenta sepals (Collectively referred to as the calyx) of the plant. The remaining study used encapsulated hibiscus powder. The main bioactives (components which exert biological effect) found in Hibiscus are thought to be the anthocyanins. These are the pigments in a fruits skin responsible for its colour and are thought to confer the most antioxidant and anti-inflammatory effects.
Looking at four of the studies, we can calculate an average blood pressure reduction of 15.34 points systolic (the first number on a blood pressure reading) and 6.59 points diastolic (the second number on a blood pressure reading) between them. Two of the studies, compared the hibiscus directly to blood pressure medication. In one of these 10g of dried hibiscus powder, standardized to 9.6mg of total anthocyanins made into a tea and taken before breakfast was found to be just as effective as 50mg of captopril. The other study which used encapsulated hibiscus powder standardized to 250mg anthocyanins, demonstrated a significant reduction in blood pressure but just fell short of the effects found with Lisinopril at 10mg.
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In adults with hypertension, 10g of Hibiscus calyx standardised to 9.6mg total anthocyanins, in a tea infusion, taken daily with breakfast over a period of four weeks, reduced Systolic and systolic blood pressure by 15.32 points 11.29 points respectively. It was found to be as effective as 50mg of Captopril.
In adults with mild hypertension, three servings of hibiscus tea daily, reduced blood pressure. After six weeks, systolic blood pressure was reduced by an average of 7.2pts diastolic and 3.1 pts diastolic. Participants with higher initial systolic blood pressure readings showed the best response.
Within 15 days of taking hibiscus tea, adults with moderate hypertension experienced a reduction of 11.2% systolic and 10.7% diastolic blood pressure. Within 3 days of stopping the treatment, systolic blood pressure increased by 7.9% with diastolic increasing by 5.6%.
In patients with type 2 diabetes, Hibiscus tea taken twice a day, for 30 days was able to reduce systolic blood pressure by 21.7 points but had no effect on diastolic blood pressure.
193 subjects with hypertension were treated with either a dried extract of Hibiscus calyxes, standardised to contain 250mg anthocyanins or 10 mg of lisinopril daily for a period of four weeks. Despite not reaching the therapeutic effectiveness of Lisinopril, the dried hibiscus reduced systolic/diastolic blood pressure by 17.14 and 11.97 points respectively.
Garlic has been renowned for it’s health benefits throughout history, with the first documented use for medicinal purposes dating back as far as 2000BC in Ancient Egypt.
There are two main varieties of garlic supplements available– traditional garlic which is the garlic we all know and love (or loath) turned into supplement form such as tablet. Then there is aged garlic extract (AGE). This is traditional garlic which has been stored at room temperature for 20 months, resulting in changes to the composition of the garlic. The main bioactives in garlic and aged garlic are though to be allicin and S-allylcystiene (SAC) respectively. Allicin produces the compounds responsible for the garlic’s unmistakable smell. Aged garlic does not contain allicin and thus produces no odour.
When we look at the studies, with the exception of one (which used a timed release garlic formula), we find that most of the traditional garlic supplements do not provide evidence of a significant reduction in blood pressure but do demonstrate significant improvements in arterial elasticity, blood flow, protection against oxidative stress and improved physical performance.
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Two groups consisting of 20 patients with essential hypertension, and 20 age/sex matched control subjects with normal blood pressure were given 250mg of garlic pearls daily for 2 months. A moderate reduction in blood pressure was noted for the hypertensive group only. This same group also experienced a significant reduction in dna damage, suggesting garlic not only reduces blood pressure but offers protection against oxidative stress in hypertensives.
42 men with high cholesterol were given either 600mg per day time release garlic tablets (Allicor) or placebo. At the 12 week mark, significant reductions in blood pressure was observed with a systolic reduction of 6.6 points and diastolic reduction of 5 points vs placebo group. The garlic group also had a 7.6% reduction in total cholesterol, which was 11.5% lower than the placebo group. LDL cholesterol levels also fell by almost 12% in the garlic group (13.8% lower than placebo) and HDL cholesterol increased by 11.5 points.
1) 900mg garlic placebo with 12g oil placebo
2) 900mg garlic with 12g oil placebo
3) 900mg garlic placebo with 12g fish oil
4) 900mg garlic with 12g fish oil
Fifty men with high cholesterol were divided into 4 groups. Those in the garlic groups had significantly lower ratios of total cholesterol to LDL whilst those given fish oil had significantly decreased triacylglycerol concentrations and increased LDL-C concentrations. Taking garlic with fish oil appeared to reverse the LDL increase induced by fish oil. The subjects had normal blood pressure levels, but despite this, a small reduction of 2.4-4.2% was observed.
Thirty patients with heart disease were given garlic supplements equivalent to 1g of raw garlic each day for six weeks. The garlic significantly (P<0.01) decreased peak heart rate and significantly reduced work load on the heart, resulting in better exercise tolerance(P<0.05). No reduction in resting blood pressure was observe, but the patients in the trial were not hypertensive
Older adults who had been taking garlic powder extracts for at least 2 years before they were studied, demonstrated improved PWV (a measure of aortic stiffness ) than those who had not been taking garlic. Differences between the groups were more pronounced, with older participants. Similar improvements were noted in the blood flow. Furthermore for any increase in blood pressure , the aorta’s elastic properties were better maintained in the garlic group vs placebo so observed PWV differences cannot, therefore, be attributed to differences in blood pressure. It is known that cholesterol increases arterial stiffness, but it does not appear that garlic’s improvement of aortic elasticity is related to it lowering cholesterol levels. Blood pressure levels were similar between groups.
Results of this study yielded no discernable difference in total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, lipoprotein concentrations, and blood pressure between the two groups
Furthermore, several clinical trials have demonstrated traditional garlic to demonstrate reliable and significant reductions in total cholesterol levels, with notable reductions in LDL cholesterol and increases in HDL (good) cholesterol.
Olive leaf extract
Coming from the plant which bears the illustrious olive fruit, olive leaf extract appears to exert anti-hypertensive effects. Whilst one study showed no effect in reducing blood pressure, another 2 studies using a standardized olive leaf formulation (EFLA943) demonstrated an average of 11 points systolic and 4 points diastolic blood pressure reduction. However, it should be noted that whilst one of the trials observed this reduction using 500mg using the EFLA943, the other trial (which tested the same formulation on twins) demonstrated no significant reduction in bp for 500mg but did observe a significant reduction for those taking 1000mg of the extract.
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Olive (Olea Europaea L.) Leaf Polyphenols Improve Insulin Sensitivity In Middle-Aged Overweight Men: A Randomized, Placebo-Controlled, Crossover Trial
Olive leaf extract with approx. 50mg oleuropein and other polyphenols improved insulin sensitivity by 15 % with a 28% improvement in pancreatic β-cell responsiveness. However, there was no significant improvement in lipid , blood pressure, or cardiovascular panels.
Olive (Olea Europaea) Leaf Extract Effective In Patients With Stage-1 Hypertension: Comparison With Captopril
One group of hypertensive patients were given Olive leaf extract(EFLA943 ) 500mg twice a day, whilst the second group received Captopril 12.5mg or 25m twice daily (The dose was increased based on subject response). After eight weeks, the olive leaf group experienced a mean reduction of 11.5 and 4.8 points in systolic and diastolic, whilst the Captopril group had a systolic reduction of 13.7 and diastolic reduction of 6.4 points. The olive leaf group experienced a small reduction in triglycerides, with no reduction observed in the Captopril group.
Food Supplementation With An Olive (Olea Europaea L.) Leaf Extract Reduces Blood Pressure In Borderline Hypertensive Monozygotic Twins
Forty identical twins with borderline hypertension were given olive leaf extract (EFLA943 . One of each twin received either 500mg or 1000mg of the olive leaf extract, whilst the other twin was given favourable lifestyle advice (control group). After 8 weeks blood pressure remain unchanged in the control group and the group given 500mg olive leaf extract whilst the group given 1000mg olive leaf extract daily experienced a mean reduction of 11 points systolic and 4 points diastolic. Cholesterol levels were reduced for all groups.
Antioxidant Effect Of Virgin Olive Oil In Patients With Stable Coronary Heart Disease: A Randomized, Crossover, Controlled, Clinical Trial
Forty males with coronary heart disease were split into two groups, one group receiving 50 ml of virgin olive oil which 8mg phenolic compounds daily, and the other receiving refined olive oil with 1mg phenolic compounds daily. The group receiving the virgin olive oil, experienced reduced systolic blood pressure (p = 0.001),reduced LDL oxidation levels and increased glutathione levels.
Several studies have also demonstrated that olive leaf can significantly reduce LDL oxidation, which is known to be a contributing factor in atherosclerosis (fat build-up in the arteries). Some of these trials have demonstrated a reduction in LDL oxidation of over 25%.
Although not technically a herb, spirulina has been the subject of studies that have attempted to evaluate it’s potential blood pressure reducing benefits. Early evidence is promising with two trials demonstrating broad spectrum cardioprotection with a reduction in blood pressure and cholesterol levels when 3.5 to 4.5g spirulina was taken daily. One trial, however, failed to show improvement in blood pressure, but this could be attributed to the relatively low dose of 1g spirulina used.
Further tests to evaluate the impact that spirulina can have on blood pressure are necessary to draw stronger conclusions, but initial evidence is certainly encouraging.
+ Show me the Studies Summary Summary Summary Spirulina may also offer other health benefits. Several Clinical trials have shown that doses of 1-8g of spirulina daily can reduce triglyceride levels by an average of 12.5% and three trials have demonstrated that spirulina may also significantly reduce lipid peroxidation (a form of oxidation that affects lipids in the body).
In a trial of patients 36 with hypertension, spirulina was observed to offer broad cardioprotection, reducing blood pressure, blood lipid concentrations, triacylglycerols and LDL cholesterol levels.
Antihyperlipemic And Antihypertensive Effects Of Spirulina Maxima In An Open Sample Of Mexican Population: A Preliminary Report
4.5g of spirulina taken daily for 6 weeks demonstrated a mean reduction in blood pressure of 8% systolic and 6% diastolic. Total cholesterol, LDL cholesterol and triacylglycerols were reduced, and HDL (good) cholesterol was increased.
The Hypolipidemic Effects Of Spirulina (Arthrospira Platensis) Supplementation In A Cretan Population: A Prospective Study
52 patients with dyslipidaemia (high levels of blood lipids) were given 1 g of spirulina per day for 12 weeks. There was no improvement in blood pressure, but total cholesterol, LDL cholesterol and triglycerides were significantly reduced.
There are other herbs that through scientific studies have been shown to improve blood pressure, but either their effect in doing so is slight compared to those we have discussed, and/or not enough trials have been carried out to validate their effectiveness. We should also mention that, although not herbal, magnesium has been shown to significantly lower blood pressure levels17,18, particularly in those who are already deficient in this nutrient.
Spirulina may also offer other health benefits. Several Clinical trials have shown that doses of 1-8g of spirulina daily can reduce triglyceride levels by an average of 12.5% and three trials have demonstrated that spirulina may also significantly reduce lipid peroxidation (a form of oxidation that affects lipids in the body).