Garlic may be useful in addition to medication to treat high blood pressure, a study suggests.
Australian doctors enrolled 50 patients in a trial to see if garlic supplements could help those whose blood pressure was high, despite medication.
Those given four capsules of garlic extract a day had lower blood pressure than those on placebo, they report in scientific journal Maturitas.
The British Heart Foundation said more research was needed.
Garlic has long been thought to be good for the heart.
Garlic supplements have previously been shown to lower cholesterol and reduce high blood pressure in those with untreated hypertension.
In the latest study, researchers from the University of Adelaide, Australia, looked at the effects of four capsules a day of a supplement known as aged garlic for 12 weeks.
They found systolic blood pressure was around 10mmHg lower in the group given garlic compared with those given a placebo.
Researcher Karin Ried said: "Garlic supplements have been associated with a blood pressure lowering effect of clinical significance in patients with untreated hypertension.
"Our trial, however, is the first to assess the effect, tolerability and acceptability of aged garlic extract as an additional treatment to existing antihypertensive medication in patients with treated, but uncontrolled, hypertension."
Experts say garlic supplements should only be used after seeking medical advice, as garlic can thin the blood or interact with some medicines.
Ellen Mason, senior cardiac nurse at the British Heart Foundation, said using garlic for medicinal purposes dates back thousands of years, but it is essential that scientific research proves that garlic can help conditions such as raised blood pressure.
She said: "This study demonstrated a slight blood pressure reduction after using aged garlic supplements but it's not significant enough or in a large enough group of people to currently recommend it instead of medication.
"It's a concern that so many people in the UK have poorly controlled blood pressure, with an increased risk of stroke and heart disease as a consequence. So enjoy garlic as part of your diet but don't stop taking your blood pressure medication."