By David Zinczenko, ABC News Nutrition and Wellness Editor

It sounds like the liquid version of Peter Parker's spider bite or Bruce Banner's Gamma rays: A magic elixir that can take you from average to super-powered with just a few sips. It's green juice: the modern-day equivalent of Popeye's spinach, in liquid form.

And for those of us looking to balance perfect health with a crazy life, it seems like a great idea: You can't eat a fruit salad while driving, or spoon up vegetable soup while walking down the street, but you can sip on organic juice and get your seven daily servings of fruits and veggies with minimal effort. And with models, athletes and celebrities being photographed toting the latest cool juice, a bottle of green has become a status symbol of the healthfully hip.

But are these juices and smoothies popping up all over really as healthy as they seem? Sure, you're getting more fruits and vegetables, but is it that easy? Is a bottle of juice as good for you as eating the real thing?

Not always. Many experts say that the very processes used to get bottled juices on the shelf may be destroying essential nutrients. And while you might not be getting the full nutritional bang for your buck, in many cases, what you are getting can hurt you: lots and lots of sugar.

Done properly though, green vegetable-dominant drinks are proven to make you leaner, happier and healthier. So what are some things you should know to help you started?

1. Make it fresh. At many trendy city juice bars, you can pay north of $10 a bottle for freshly squeezed juice. But even a seemingly fresh and healthy upscale juice can be packed with extra sugars. (See my analysis of Juice Press's Dr. Green, below.) Don't assume that just because you're paying an arm and a leg, you're going to get something that's making your arms and legs (and the rest of you) leaner and healthier. You can buy a juicer for less than $100 and begin maximizing your nutrition at home. For more tips and recipes, check out Candice Kumai's latest book: Clean Green Drinks. Or look for a juice bar where you can customize your drink and watch them make it in front of you.

2. Keep it green. Fruits add sweetness to juices, which is great for beginners getting used to the idea of an all-veggie juice; but they can also add a lot of sugar. Adding too many fruits can easily turn your healthy drink into a high-sugar dessert that spikes blood insulin levels and leaves you sluggish. In fact, just one serving of fruit juice a day can increase your risk of developing type 2 diabetes by as much as 21 percent, according to Harvard researchers. A tall glass of fruit juice can pack around 50 grams of sugar - more than twice the daily recommendation of the American Heart Association for women, and more than a full day's worth for men. As a rule of thumb, see that the majority of ingredients in your juice is green in color. (Cucumber and celery are low-calorie ways of adding sweetness to your drink.)

3. Drink your juice right away. To get the most bang for your buck, consume your clean green drink within twenty minutes of juicing or ordering at the juice bar. Here's why: As soon as you juice produce, you break open every cell wall of the fruits and vegetables, and from the moment they are exposed to air, their enzymatic and nutritional values begin to deteriorate. It's a process known as oxidation, which is simply exposure to oxygen. Think about a freshly cut apple that browns over time. A blended juice or smoothie is even more susceptible to oxidation, since every part of the produce has been exposed to air. Because of this, bottled juices are pasteurized to prevent oxidation and preserve freshness. Some medical experts suggest consuming green juices on an empty stomach, which allows your body to quickly and easily quickly absorb all the nutrients without other food interfering. Juicing in the morning is a great way to start the day with a huge nutritional boost, without taxing your digestive system.

4. Chew and savor your juice. Sounds crazy, right? In fact, chewing and swirling your green drink in your mouth is an important part of the digestive process. That's because saliva contains the enzyme Ptyalin, which helps to break down food and speed up chemical reactions. A recent study by Purdue University showed a direct relationship between small particle size and increased nutrient uptake. In other words, the more you chew, the more nutrients are retained in the body.

5. Beware the health halo. As I mentioned above, a lot of commercially available drinks seem healthful, but not when you study the ingredients list. Here's a breakdown of four popular brands, and what you should-and what you should think twice about - slurping:

JAMBA JUICE

You walk into Jamba Juice and order a blended juice of Kale Apple Pineapple and Chia Seeds. And you think you're doing yourself a favor. (It's got kale in it!) But in fact, you're actually getting 43 grams of sugar - more than twice as much as the American Heart Association wants women to have in an entire day and more than a day's worth for men! 5 If you're drinking fruit juice, either opt for a small, or choose the carrot juice and save yourself 23 grams of sugar.

Instead of This …

Kale Apple Pineapple and Chia Seeds Juice Blend (16 oz)

250 calories, 2 g fat, 2 mg sodium, 5 g fiber, 43 g sugar, 4 g protein

Try This …

Carrot Juice (12 oz)

100 calories, .5 g fat, 170 mg sodium, 0 fiber, 20 g sugar, 3 g protein

NAKED JUICE

So you want to eat more brightly-colored fruits for their cleansing and health properties and you pick up a Naked Pomegranate Blueberry juice. Well, the label might lead you to believe that you're getting 32 grams of sugar (which is already more than you should be getting in a day if you're a woman and almost a day's worth if you're a man). But, then you have to read the label closely to see that if you drink the whole bottle you're getting almost twice that much. So, it's actually 61 grams of sugar! Naked just started offering a new "power garden" line, and their Tomato Kick has just 114 calories and 17 grams of sugar per bottle.

Instead of This …

Naked Pomegranate Blueberry (serving size 8 oz, 2 suggested servings per container) Calories, sodium, sugar and protein per 15.2 oz bottle: 285 calories, 0 g fat, 38 mg sodium, 0 g fiber, 61 g sugar, 2 g protein

Try This …

Naked Tomato Kick Power Garden (serving size 8 oz, 2 suggested servings per container) Calories, sodium, sugar and protein per 15.2 oz bottle: 114 calories, 0 fat, 380 mg sodium, 6 g fiber, 17 g sugar, 4 g protein

SMOOTHIE KING

So, let's say that you're not going to Smoothie King for a 40 oz "smoothie meal" that could cost you 1928 calories and 250 grams of sugar (that would be their Hulk Strawberry Smoothie), and instead you're looking for a small, refreshing fruit smoothie. Well, all of their "small" options are going to cost you a couple days' worth of sugar: their 20 oz Pomegranate Punch has 396 calories and 96 grams of sugar (that's almost 4 days worth of sugar for the ladies and 2 and a half day's worth for the men). Your best bet here is to go for the Kids' Kups Choc-A-Laka (a blend of vanilla yogurt and chocolate). It's not really a juice, but it's the only thing on the menu with less than a day's worth of sugar.

Instead of This …

Pomegranate Punch (20 0z)

396 calories, 0 fat, 96 grams of sugar

Try This …

Kids' Kups Choc-A-Laka (12 oz)

210 calories, 15 g sugar

JUICE PRESS

You're paying eleven dollars for a bottle of juice, it better be healthy, right? Well, a bottle of Juice Press's Dr. Green Juice says that it has 19 grams of sugar and 120 calories per serving. That seems pretty good-until you realize a serving is half a bottle! Drink a whole bottle and you've exceeded the daily allotment of sugar for an adult female, and downed 240 calories. Another thing to consider is this blend of red apple juice, pineapple juice, kale juice, lemon juice, and ginger juice could be made at home for about $1.90 per serving.

On the other hand, a whole bottle of their Mother Earth juice (cucumber, celery, kale, swiss chard, dandelion, parsley, lemon, ginger juice) is just 120 calories with only 6 grams of sugar.

Instead of This …

Dr. Green

240 calories, 1 g fat, 60 mg sodium, 1 g fiber, 36 g sugar, 4 g protein

Try This …

Mother Earth

120 calories, 2 g fat, 320 mg sodium, 0 fiber, 6 g sugar, 8 g protein

David Zinczenko is ABC News Nutrition and Wellness Editor and the author of " Eat It to Beat It! " To discover more hidden sources of sugar, and how to lose weight by skipping other ingredients in our everyday food, check out "Eat It to Beat It!" here .