A tall glass of kale?

It might sound strange, but a growing number of people are drinking their daily quota of vegetables and fruits — and say their health is better for it.

Known as juicing, the concept is simple: Extract the juices of nutrient-rich fruits and veggies, and drink it. The practice is fast becoming a $5 billion industry in the U.S., according to Barron’s, and is only expected to grow.

Fans of juicing say they think the body absorbs nutrients better from raw juices and gets a boost of energy. Especially popular right now are green juices — made with dark leafy greens such as kale, chard and spinach. Though fruits are used to sweeten these juices, they are done so sparingly to avoid adding calories.

Amy Pierce, 41, of Sterling Heights, Mich., began juicing a year ago. She credits Joe Cross’ 2010 documentary “Sick, Fat and Nearly Dead,” which chronicles how juicing helped him combat a medical condition, lose weight and get healthy.

“I never thought much about juicing before that (documentary),” Pierce says. “And I didn’t know if I wanted to invest in it — you can spend thousands on juicers.”

Pierce, who follows a plant-based diet, bought a second-hand Jack LaLanne juicer and juices at least three times a week. She sticks mainly to one green juice, using kale, red, orange or yellow bell pepper, cucumber, lemon, and orange or red grapefruit.

“It’s that smoothness you get from the juicers,” Pierce says. “(The juice) is very clean-tasting and smooth, and I really like that.”

Home juice extractors aren’t cheap.

An average one can cost $70; higher-end models cost as much as $400 or more. But the price hasn’t dampened sales.

From November 2011 to November 2012, sales of home juice extractors increased 71 percent, according to the NPD Group, a market research firm.

Registered dietitian Rebecca Da Silva of Beaumont’s Weight Control Center in Royal Oak, Mich., says she has seen increased interest in juicing, with more patients asking her about the practice in the last year.

“Used effectively to help get in more fruits and vegetables, it’s an acceptable way,” Da Silva says. “Juicing fruits has been around forever, but more people are now juicing vegetables with their fruit.”

But, she cautioned, you can get in a lot of calories if you over do it, especially with fruits.

“You should be mindful of the fruits you are putting in the juices,” Da Silva says. “The fruits, with their natural sugar, can add more calories.”

And, Da Silva says, you need to be mindful if the juicer you use extracts only the juice.

“If you’re using a juicer that takes some of the pulp out, you are losing out on some of the nutritional value,” she says. “Some of the fiber is in the skin and some in the flesh, and most of the pulp gives you fiber.”

Consuming fiber, Da Silva says, helps control hunger because it helps you feel fuller longer. “And that can help you lose weight.”

Not everyone who juices does so at home. There are stores where people can buy organic, raw and cold-pressed bottled juices.

The downside to fresh, raw juices: They are not pasteurized. They have no preservatives and should be consumed soon after they’re made for both nutritional value and food safety issues.

“They are all organic. No matter what you get, it will last for 72 hours,” says Caitlin James, an owner of Drought in Plymouth, Mich., where workers make juices to order in small batches.

At Cacao Tree Cafe in Royal Oak, Mich., owner Amber Poupore says her store sells green juices including those with a shot of wheatgrass. She notes that customers want them because they are seeking alternatives for better health.

“Our intention was more of a healthy, lower glycemic juice,” Poupore says. “So instead of the carrot, we have cucumber- and celery-based juices.”

Poupore says the benefit of wheatgrass (made in a special juicer) is that 1 ounce is comparable to consuming 2½ pounds of dark leafy greens.

And if juicing is a way of getting more greens in your diet, Pierce believes it is worth a try.

“It’s morning, and you’ve already had a cup of greens,” Pierce says. “How great is that?”

KALE GREEN JUICE

Servings: Three to four

Total time: 15 minutes

1 bunch of kale

1 bunch of spinach

3 to 4 ribs of celery and leaves

1 green apple, pear or spear of fresh pineapple

1 whole peeled lemon (save the peel for its zest )

1 piece (about 2 inches) of ginger

Half a hothouse cucumber (unpeeled)

Clean and wash vegetables and fruit. Process in a juice extractor.

WHAT IS A JUICE EXTRACTOR?

Juice extractors are kitchen appliances that extract the juice from whole fruits and vegetables. The pulp and skin are left behind, which, health experts say, is something people should keep in mind when juicing. That pulp and skin can contain key nutrients as well as fiber.

For home use, there are two kinds of juice extractors that work differently: Centrifugal and masticating juicers. Both look about the same.

• Centrifugal: This is the most common type of juicer sold at kitchen stores and big box retailers. It’s the most affordable. Once you feed in the vegetables or fruit, it shreds and spins very fast so that the pulp and bits of fruit and vegetables are caught by a strainer or filter and the juice spins out. Centrifugal juicers can be loud. And, because they are fast, they heat up, which can affect the nutritional value of the juice.

Masticating: These juicers have an auger that crushes or grinds the fruit and vegetables. The crushed fruit and vegetables are pressed against a filter or strainer. Masticating juicers run slower so they don’t heat up and destroy the nutrients in the juice. These are known to create pulp that’s drier than that left by centrifugal models.

WANT TO BUY ONE? In “America’s Test Kitchen: The TV Companion Cookbook 2013″ (America’s Test Kitchen, $34.95), editors rated four centrifugal and two masticating juicers. The Breville Juice Fountain Plus centrifugal machine, $149.99, came out on top as the highly recommended juicer.