New York, Dec 12 (IANS): Carrots are a good source of beta-carotene, which is a precursor of vitamin A and to get the full health benefits of this superfood, we need an active enzyme to produce this vitamin, say researchers.

Beta-carotene is the bioactive compound that gives carrots their orange colour. Studies with humans and mice show the conversion of beta-carotene to vitamin A reduces "bad" cholesterol in the blood.

"Thus, beta-carotene can help protect against atherosclerosis development, which leads to the accumulation of fats and cholesterol in our arteries. Atherosclerosis cardiovascular disease is the primary cause of death worldwide," said study author Jaume Amengual from the University of Illinois in the US.

The research team conducted two studies to further understand the effects of beta-carotene on cardiovascular health. They confirmed its importance but identified a critical step in the process.

Beta-carotene converts to vitamin A with the help of an enzyme called beta-carotene oxygenase 1 (BCO1).

"A genetic variation determines if you have a more or less active version of BCO1. People with a less active enzyme could need other sources for vitamin A in their diet, Amengual said.

The first study, published in the Journal of Nutrition, analysed blood and DNA samples from 767 healthy young adults aged 18 to 25.

As expected, the researchers found a correlation between BCO1 activity and bad cholesterol level.

"People who had a genetic variant associated with making the enzyme BCO1 more active had lower cholesterol in their blood. That was our first observation," Amengual noted.

To follow up on these findings, the team conducted a second study, published in the Journal of Lipid Research, using mice.

"The main findings of the mice study reproduce what we found in humans. We saw that when we give beta-carotene to mice, they have lower cholesterol levels," the authors wrote.

These mice develop smaller atherosclerosis lesions, or plaques, in their arteries.

"This means that mice fed beta-carotene are more protected against atherosclerosis than those fed a diet without this bioactive compound," Amengual stated.