Clinical Inquiries

Does evidence support the use of supplements to aid in BP control?

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EVIDENCE-BASED ANSWER:

Yes. A number of well-tolerated natural therapies have been shown to reduce systolic and diastolic blood pressure (BP). (See Table1-8 for summary.) However, the studies don’t provide direct evidence of whether the decrease in BP is linked to patient-oriented outcomes. Nor do they allow definitive conclusions concerning the lasting nature of the reductions, because most studies were fewer than 6 months in duration (strength of recommendation: C, disease-oriented evidence).


 

References

EVIDENCE SUMMARY

Cocoa. A 2017 Cochrane review evaluated data from more than 1800 patients (401 in hypertension studies) to determine the effect of cocoa on BP.1 Compared with placebo (in flavanol-free or low-flavanol controls), cocoa lowered systolic BP by 1.8 mm Hg (confidence interval [CI], –3.1 to –0.4) and diastolic BP by 1.8 mm Hg (CI, –2.6 to –0.9). Further analysis of patients with hypertension (only) showed a reduction in systolic BP of 4 mm Hg (CI, –6.7 to –1.3).

How well do these supplements aid in BP control?

Omega-3 fatty acids. Similarly, a 2014 meta-analysis investigating omega-3 fatty acids (eicosapentaenoic acid [EPA] + docosahexaenoic acid [DHA]) included data from 4489 patients (956 with hypertension) and showed reductions in systolic BP of 1.5 mm Hg (CI, –2.3 to –0.8) and diastolic BP of 1 mm Hg (CI, –1.5 to –0.4), compared with placebo.2 Again, subgroup analysis of patients with hypertension (only) at baseline revealed a greater decrease in systolic and diastolic BP: 4.5 mm Hg (CI, –6.1 to –2.8) and 3.1 mm Hg (CI, –4.4 to –1.8), respectively.

How well do these supplements aid in BP control?

Garlic and potassium chloride. Separate meta-analyses that included only patients with hypertension found that both garlic and potassium significantly lowered BP.3,4 A 2015 meta-analysis comparing a variety of garlic preparations with placebo in patients with hypertension showed decreases in systolic BP of 9.1 mm Hg (CI, –12.7 to –5.4) and in diastolic BP of 3.8 mm Hg (CI, –6.7 to –1).3 Meanwhile, a meta-analysis in 2017 comparing different doses of potassium chloride with placebo demonstrated reductions in systolic BP of 4.3 mm Hg (CI, –6 to –2.5) and diastolic BP of 2.5 mm Hg (CI, –4.1 to –1).4

L-arginine. Another meta-analysis of randomized controlled trials reported evidence that oral L-arginine, compared with placebo, significantly reduced systolic BP by 5.4 mm Hg (CI, –8.5 to –2.3) and diastolic BP by 2.7 mm Hg (CI, –3.8 to –1.5).5 Close to one-third of patients had hypertension at baseline.

Beetroot juice. A double-blind, placebo-controlled study showed that consumption of beetroot juice (with nitrate) once daily reduced BP in 3 different settings (clinic, 24-hour ambulatory, and home readings) when compared with placebo (nitrate-free beetroot juice).6 Study participants were mostly British women, overweight, without significant c­ardiovascular or renal disease, and with uncontrolled ambulatory BP (> 135/85 mm Hg).

Flax seed. A prospective, double-blind trial of patients with peripheral artery disease compared the antihypertensive effects of flax seed with placebo in patients with and without hypertension and found marked decreases in systolic and diastolic BP.7 Study participants were all older than 40 years without other major cardiac or renal disease, and the majority of enrolled patients with hypertension were concurrently taking medications to treat hypertension during the study.

Olive leaf extract. A double-blind, parallel, and active-control clinical trial in Indonesia compared the BP-lowering effect of olive leaf extract (Olea europaea) to captopril as monotherapies in patients with stage 1 hypertension.8 After a 4-week period of dietary intervention, individuals who were still hypertensive (range, 140/90 to 159/99 mm Hg) were treated with either olive leaf extract or captopril. After 8 weeks of treatment, both groups saw comparable reductions in BP.

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