NEW YORK – At midmorning, the line at Liquiteria is almost out the door.

Customers at the bright, cheerful New York City juice bar can't seem to get enough of owner Doug Green's menu of smoothies and fresh-squeezed juices. Some of the drinks are billed as energy builders; others promise to burn fat, boost the immune system or detoxify the lymph system. But hard-core juicers don't need to trek to this trendy East Village neighborhood where Liquiteria has been serving a loyal clientele since 1996. There are dozens of juice bars all over the country, including more than 700 branches of the California- based Jamba Juice.

Today there are more than 6,400 outlets across the U.S. that sell fresh juice and smoothies, ringing up $3.4 billion in annual sales, according to industry consulting group Juice Gallery Multimedia. It's a far cry from the early days, when juice bars were often drab affairs tucked in the back of health food stores.

Personal trainer Neil Mitchell started making vegetable juice about 15 years ago. His blend includes carrots, beets, kale, broccoli, parsley, celery and ginger, and he believes it boosts his energy.

"It's a hard thing to describe but you just feel healthier," he said. "When I was in my late 20s I used to wake up with stiff joints. ... That went away in about five weeks. It absolutely disappeared."

Whether drinking fresh juice every day delivers all the health benefits that advocates claim is a matter of debate. Nutrition experts say Americans in general don't eat enough fruits and vegetables, so they applaud any diet that increases servings of those two vital food groups.

As for the more extravagant claims made by some proponents that fresh-squeezed vegetable juice detoxifies organs and cleanses the digestive tract, medical professionals are skeptical.

"I honestly don't understand the concept of intestinal cleansing. It's not like you'd find old tin cans or spare tires in the colon," said Dr. Edward Saltzman, a research scientist at the Jean Meyer USDA Human Nutrition Research Center at Tufts University.

Local juice joints

Jamba Juice, various locations. jambajuice.com.

Bliss Raw Cafe and Elixir Bar, 6855 Greenville Ave. 214-987-0204. blissrawcafe.com.

Roy's Natural Market, 6025 Royal Lane, Suite 130