An old, sprouting garlic bulb has more heart-healthy antioxidants than its fresher counterparts, U.S. researchers said.

People have used garlic for medicinal purposes for thousands of years, and eating garlic or taking garlic supplements is often touted as a natural way to reduce cholesterol levels, blood pressure and heart disease risk, Jong-Sang Kim of the School of Food Science and Biotechnology at the Kyungpook National University in Daegu, South Korea, and colleagues said.

The researchers said other studies showed sprouted beans and grains had increased antioxidant activity, so the team set out to see if the same was true for garlic.

The researchers found garlic sprouted for five days had higher antioxidant activity than fresher, younger bulbs. It also had different metabolites, suggesting it makes different substances.

Extracts from this garlic even protected cells in a laboratory dish from certain types of damage.

"Therefore, sprouting may be a useful way to improve the antioxidant potential of garlic," the researchers said in the study.