Researchers from the US Department of Agriculture have found that herbs are an abundant source of antioxidants and could provide potential anticancer benefits when supplementing a balanced diet.
The research, published in the Journal of Agricultural and Food Chemistry, a peer-reviewed journal of the American Chemical Society, showed that herbs have higher antioxidant activity than fruits, vegetables and some spices, including garlic.
"Some herbs should be considered as regular vegetables," said Shiow Y. Wang, Ph.D., the study's lead researcher and a biochemist with the USDA's Beltsville Agricultural Research Center in Beltsville, Md. "People should use more herbs for flavouring instead of salt and artificial chemicals."
Using various chemical tests, Wang studied and compared the antioxidant activity of 39 commonly used herbs grown in the same location and conditions. The study, which did not involve animal or human subjects, included 27 culinary and 12 medicinal herbs.
The herbs with the highest antioxidant activity belonged to the oregano family, the research showed. In general, oregano had three to 20 times higher antioxidant activity than the other herbs studied.
On a per gram fresh weight basis, oregano and other herbs ranked even higher in antioxidant activity than fruits and vegetables, which are known to be high in antioxidants. Oregano has 42 times more antioxidant activity than apples, 30 times more than potatoes, 12 times more than oranges and four times more than blueberries, Wang said.
Other herbs were also found to be high in antioxidants, including dill, garden thyme, rosemary and peppermint.
The most active phenol component in some of the herbs with the highest antioxidant activity, particularly oregano, was rosmarinic acid, a strong antioxidant.
Antioxidants are a class of compounds thought to prevent certain types of chemical damage caused by an excess of free radicals, charged molecules that are generated by a variety of sources including pesticides, smoking and exhaust fumes. Destroying free radicals may help fight cancer, heart disease and stroke, researchers believe.
Fruits and vegetables have long been viewed as a rich source of antioxidant compounds. Health officials have been urging consumers for years to eat more fruits and vegetables in order to gain the health benefits of antioxidants, but progress has been slow, according to researchers. Westerners still tend to favour diets that are rich in fats and carbohydrates, they say.
More recently, researchers have begun to formally study the health benefits of herbs and spices. The two differ mainly by source. Herbs typically come from the leaves of plants. Spices come from the bark, stem and seeds of plants. Both have been used for thousands of years to flavour foods and treat illness.
In general, fresh herbs and spices are healthier and contain higher antioxidant levels compared to their processed counterparts, according to Wang. For example, the antioxidant activity of fresh garlic is 1.5 times higher than dry garlic powder.
Just as consuming too much of any food product can carry health risks, herbs should be used with moderation, Wang cautioned. Herbs are no substitute for a balanced diet, she added, and pregnant women in particular should consult their physicians before taking herbal supplements.