Benefits
Blood pressure within the normal range
In a 6-week trial in adults with prehypertension, 300 mg/day lowered systolic pressure more than placebo, with values returning to baseline after stopping. The largest trial (70 adults, 300 mg/day for 8 weeks) found a 3.0 mmHg systolic difference that was not statistically significant, and EFSA judged the overall evidence insufficient.
Ambulatory blood pressure over four weeks
A three-arm trial in 27 adults with metabolic syndrome reported lower blood pressure at 150 and 300 mg/day over 4 weeks. Only changes within each group were analysed and starting pressures differed markedly between groups, so EFSA could draw no conclusions from it.
Mechanism of action
Proposed blood vessel relaxation
The applicant to EFSA proposed that the extract supports normal blood pressure by relaxing blood vessels through the vessel lining. In the trials, flow-mediated dilation and vasoactive markers did not change, and EFSA found that a plausible mechanism in humans had not been established.
Polyphenol composition
Most of the extract's phenolics are oligomers (about 69%), with smaller shares of monomers such as catechin and epicatechin (about 9%) and polymers (about 22%).
Clinical trials
Randomized, three-arm, placebo-controlled trial of 150 or 300 mg/day for 4 weeks with ambulatory blood pressure monitoring; EFSA identified the extract as MegaNatural-BP. (Sivaprakasapillai et al. 2009, Metabolism)
27 adults with metabolic syndrome, 9 per group.
The authors reported lower systolic and diastolic pressure with the extract and no change in lipids or glucose. EFSA noted that only within-group changes were analysed and that starting pressure differed markedly between groups, and it drew no conclusions from this trial.
Randomized, double-blind, placebo-controlled parallel trial of 300 mg/day in a juice drink for 6 weeks, then 4 weeks without it. The abstract does not name the brand; EFSA identified it as MegaNatural-BP. (Park et al. 2016, Br J Nutr)
36 adults with prehypertension randomized; 29 completed (12 in the extract group).
Systolic pressure fell 5.6% and diastolic 4.7% within the extract group. The systolic change differed from placebo (P = 0.03); the diastolic difference did not reach significance (P = 0.08). Pressure returned to baseline after stopping, and flow-mediated dilation, lipids, glucose and oxidized LDL did not change.
Randomized, double-blind, placebo-controlled parallel trial of 300 mg/day for 8 weeks, the largest trial; EFSA identified the extract as MegaNatural-BP. (Ras et al. 2013, Br J Nutr)
70 untreated adults with systolic pressure of 120 to 159 mmHg.
No significant effect: versus placebo, systolic pressure changed by -3.0 mmHg and diastolic by -1.4 mmHg, neither statistically significant. ADMA, plasma renin activity and platelet aggregation were unaffected.