Researchers have cracked the mystery of why eating garlic can help keep the heart healthy.
The smell may be a healthy sign
The key is allicin, which is broken down into the foul-smelling sulphur compounds which taint breath.
These compounds react with red blood cells and produce hydrogen sulphide which relaxes the blood vessels, and keeps blood flowing easily.
The University of Alabama at Birmingham research appears in Proceedings of the National Academy of Sciences.
However, UK experts warned taking garlic supplements could lead to side effects.
Hydrogen sulphide generates a smell of rotten eggs and is used to make stink bombs.
But at low concentrations it plays a vital role in helping cells to communicate with each other.
And within the blood vessels it stimulates the cells that form the lining to relax, causing the vessels to dilate.
This, in turn, reduces blood pressure, allowing the blood to carry more oxygen to essential organs, and reducing pressure on the heart.
The Alabama team bathed rat blood vessels in a bath containing juice from crushed garlic.
This produced striking results - with tension within the vessels reduced by 72%.
The researchers also found that red blood cells exposed to minute amounts of juice extracted from supermarket garlic immediately began emitting hydrogen sulphide.
Further experiments showed that the chemical reaction took place mainly on the surface of the blood cells.
The researchers suggest that hydrogen sulphide production in red blood cells could be used to standardise dietary garlic supplements.
Lead researcher Dr David Kraus said: "Our results suggest garlic in the diet is a very good thing.
"Certainly in areas where garlic consumption is high, such as the Mediterranean and the Far East, there is a low incidence of cardiovascular disease."
Judy O'Sullivan, a cardiac nurse at the British Heart Foundation, said: "This interesting study suggests that garlic may provide some heart health benefits.
"However, there remains insufficient evidence to support the notion of eating garlic as medicine in order to reduce the risk of developing coronary heart disease.
"Having garlic as part of a varied diet is a matter of personal choice.
"It is important to note that large amounts in supplement form may interact with blood thinning drugs and could increase the risk of bleeding."