However, raw or cooked garlic, and garlic powder are not as effective in treating high blood pressure as aged garlic extract.
In a 12-week trial involving 50 people, Dr Karin Ried's team found that those with systolic blood pressure above 140 who took aged garlic extract capsules experienced an average systolic blood pressure 10.2mmHg lower than the control group, who took a placebo.
"This reduction is clinically significant, as a drop in systolic blood pressure by 5 mmHg reduces the risk of cardiovascular disease by 8-20%," Dr Ried says.
"Garlic is thought to have an antihypertensive effect because it stimulates production of certain chemical substances called nitric oxide (NO) and hydrogen sulphide (H2S), which helps relax blood vessels."
The results of the team's study have been published in Maturitas, an international peer-reviewed scientific journal produced by Elsevier, the world's largest publisher of science and health information.
"High blood pressure is an important risk factor for cardiovascular disease," Dr Ried says. "About 30% of adults in Australia are hypertensive, yet only half that number are on BP medication and 60% of those who are receiving treatment are inadequately controlled."
Dr Ried says high blood pressure is the most frequently managed problem in Australian general practice, accounting for almost 10% of GP visits.
"This statistic, coupled with the fact that Australians are comfortable with using complementary and alternative medicine, shows there is plenty of scope to explore the use of garlic as an effective treatment option for people suffering hypertension."
Last month, Dr Ried and her colleagues created worldwide attention for another study which found that dark chocolate was also effective in reducing high blood pressure.
