Two familiar plant compounds found in onions, berries and turmeric appear to lower blood pressure by acting on several biological systems at the same time, not through a single mechanism. That is the takeaway of a review published August 20, 2026, in the peer-reviewed journal Phytotherapy Research by a team of Chinese researchers led by Qiqi Deng.
The review pulls together evidence on plant-derived compounds including quercetin, curcumin, resveratrol and berberine. Its central argument is that they hit overlapping pathways: direct effects on vascular tone, dampening of inflammation and oxidative stress, and changes to the kidney's blood-pressure signaling.
That matters for a very ordinary American problem. High blood pressure affects nearly half of US adults, and only about one in four has it under control, according to the Centers for Disease Control and Prevention. It is a leading driver of heart disease and stroke.
How the compounds may lower pressure
Quercetin is a flavonoid found in onions, apples, berries, capers, tea and red wine. A review in the journal Pharmaceuticals laid out several proposed mechanisms.
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It appears to inhibit angiotensin-converting enzyme, improve the endothelium's release of nitric oxide (a molecule that relaxes blood vessels), reduce oxidative stress, and act directly on vascular smooth muscle to trigger relaxation.
Animal work in that review showed a roughly 31 percent drop in ACE activity after quercetin treatment, comparable to standard ACE inhibitor drugs.
Curcumin, the yellow pigment in turmeric, is thought to lower blood pressure mainly by improving endothelial function and calming inflammation in the vessel wall. Both compounds also converge on the renin-angiotensin system, the hormonal loop the kidneys use to regulate pressure and fluid balance.
What the human trials actually show
The human evidence is more modest than the mechanistic story. A 2016 meta-analysis in the Journal of the American Heart Association pooled seven trials with 587 patients and found a weighted mean reduction of 3.04 mm Hg in systolic and 2.63 mm Hg in diastolic blood pressure with quercetin supplementation. The effect was stronger at doses above 500 mg per day, well beyond what most people get from food.
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Curcumin has been harder to pin down. Recent meta-analyses suggest turmeric and curcumin supplements can modestly improve blood pressure and endothelial function, though the effect looks clearest in people who already have diabetes or hypertension.
None of this proves cause and effect. Deng and colleagues wrote a review, not a trial, and reviews cannot establish causation. Human trials so far have been small, doses vary widely, and both compounds are poorly absorbed from food alone.
What it means for your plate
Getting meaningful quercetin from food is realistic. Red onions carry around 39 mg per 100 grams, and elderberries, blueberries and apple peel are also concentrated sources. Curcumin is a harder case. It makes up only a small share of turmeric by weight, and it is barely absorbed unless combined with fat or with piperine, the active compound in black pepper.
Supplements can hit the doses used in trials, but they come with caveats. The National Center for Complementary and Integrative Health considers conventionally formulated turmeric or curcumin likely safe in recommended amounts for up to two or three months.
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It also warns that formulations engineered for enhanced bioavailability have been linked to liver injury in some users. We have looked at what high-dose curcumin can do to your liver in more detail.
People taking blood pressure or blood-thinning medication should talk to their doctor before adding either supplement, because both can interact with drugs the kidneys and liver process. Neither compound is a substitute for the basics that carry the strongest evidence for managing blood pressure: weight control, sodium reduction, exercise and, where indicated, prescribed medication.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.