The discovery means that readily available over-the-counter supplements could be used to help save lives.
Figures show that high blood pressure - also called hypertension - is responsible for up to 40 per cent of the 150,000 strokes every year and tens of thousands of heart attacks.
But, in the latest research, patients suffering from the condition who took garlic supplements every day for up to five months saw their blood pressure levels drop significantly.
In some cases, the drop was as much as that seen in patients taking drugs such as beta-blockers and ACE inhibitors. However, researchers have yet to establish whether garlic supplements are as effective as prescribed medicines when used for many years.
"I think this is interesting research as it shows a reasonably consistent effect. The reduction in blood pressure is not trivial, it is the same as gained from taking pills," The Daily Express quoted Dr Tim Chico, a cardiologist and academic from the Centre for Developmental and Biomedical Genetics at Sheffield University, as saying.
"What we do not know is if garlic works as well as pills over the long term or if it would reduce the risk of heart attack or stroke. But I was surprised at the extent of blood pressure reduction seen with garlic.
"There is no harm in taking garlic along with other lifestyle factors such as eating less red meat, less salt, less alcohol and taking more exercise and also continuing to take blood pressure medication," Chico added.
People can reduce blood pressure by cutting their intake of salt, losing weight and getting fit.
But many still need to be placed on medication to reduce their blood pressure readings to the safe level of 140/90.
Dr Karin Ried, of the University of Adelaide, examined 11 studies in which patients were randomly assigned to garlic or a placebo.
The higher a person's blood pressure was at the beginning of the study, the more it was reduced by taking garlic.
Dr Rosemary Leonard, the Daily Express doctor, said: "Anyone could benefit from regular doses of garlic, but it is important not to assume that taking supplements is all you need to treat high blood pressure.
"If you have high blood pressure and are overweight, then it is important to take regular exercise and eat a healthy diet."