Juice was pretty simple when I was a kid. My parents gave me apple or orange juice for a boost of vitamin C. Sure, they knew it had sugar, but they mostly worried about that in terms of dental cavities. But now we know there are other important reasons to be concerned about how juice operates as a sugar-conveyance system.

All fruit juice - whether it's apple, orange, grape or a fancy blend such as peach-mango-blueberry - is high in sugar. An eight-ounce serving of juice and cola both contain about 30 grams of sugar on average - that's almost eight teaspoons. Plus, most commercial juice eliminates wholesome fruit parts like skin and pulp. And goodbye, fiber. Smoothie blends made from whole fruit may have a gram or two of fiber, but just as much sugar as any other juice. It's better to eat whole fruit instead - to get more fiber and cut down on sugar.

Consider this: You aren't likely to eat three apples in one sitting, but it's easy to drink the equivalent of three apples in eight ounces of juice. With a sugar avalanche such as that, your body doesn't care where it comes from. Too much is too much, regardless of the source.

Yes, fruit juice contains "natural" sugar - but that does not make it healthier than the sugar in cola. In fact, the World Health Organization doesn't even classify the sugar in juice as natural sugar. Instead, it's grouped with "free sugars," just like the sugar in soda.

WHO recommends adults and children reduce intake of free sugars to less than 10 percent of total calories. For an adult consuming 2,000 calories daily, that's no more than 50 grams (or 12 teaspoons) of free sugars per day from all sources - be it candy, baked goods, soda or juice. It's even less for kids - maybe eight or nine teaspoons. Getting more than 10 percent of calories from free sugars is linked to an increased risk of cardiovascular disease, stroke, Type 2 diabetes, dental cavities and some types of cancer.

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Kids consume more juice than any other age group, which is problematic if it displaces other nutritious foods. The American Academy of Pediatrics says it's not necessary to offer children any juice. If you do, it recommends no juice before age 1, then its guidelines state that "the intake of juice should be limited to, at most, 4 ounces/day in toddlers 1 through 3 years of age, and 4 to 6 ounces/day for children 4 through 6 years of age." After age 7, it recommends a maximum of eight ounces per day. (I think that's too much and recommend water instead).

There is one bright spot: Fruit juice does offer some nutrients. Studies show drinking no more than five ounces a day is linked to a lower risk of heart disease and stroke. So a small amount of fruit juice seems to be OK, but too much sugar from all sources - including juice - is linked to poor health outcomes.

What about commercial vegetable juice? Options such as the traditional savory tomato-based concoction have just two teaspoons of sugar for eight ounces, but a whopping 650 milligrams of sodium. That's not a nutritious swap for fruit juice.

More recently, vegetable juice has been reinvented to include a nutritious array of cold-pressed elixirs that are low in sugar and have no added salt. Celery-parsley tonic, anyone? People are investing in cold-press masticating juicers for their home kitchens, and juice bars are popping up across the country, offering an array of single-serve bottles in the $10 range.

Is it nutritious to sip a beverage made from low-sugar leafy greens, celery, cucumber and ginger? Sure, if you can afford to. For relatively few calories and less than a teaspoon of sugar per cup, you get a variety of vitamins, minerals and antioxidants in a hydrating beverage. It's a good option for people who struggle to eat enough vegetables, and it's definitely a better choice than sugary fruit juice. Just watch out for high-sugar vegetables as ingredients (carrots, sweet potatoes, beets) or vegetable juice blended with fruit for palatability.

Cold-pressed juices are said to be more nourishing than traditional commercial juices from concentrate because they undergo less processing and are not heat-pasteurized, meaning they retain more nutrients. I haven't seen any clinical studies ably comparing the nutritional benefits of cold-pressed vs. juice from concentrate, so exact measures are not available.

But keep this in mind: Most commercial juice sold in the United States is pasteurized to reduce the risk of bacteria such as E. coli or salmonella. Cold-pressed juice makers may skip this step to preserve nutrients, but then the juice could contain bacteria, making it a classic Catch-22. There's a low risk of getting sick because most people's immune systems can usually fight off the bacteria, but the AAP cautions parents to avoid offering children unpasteurized juice, because their still-developing immune system is more likely to react. Unpasteurized juice sold in supermarkets is easy to identify because it carries a warning label stating the potential harm, but this label does not appear on juice from farmers markets or juice bars.

One solution is to ensure you buy cold-pressed vegetable juice made using a system called high-pressure processing, or pascalization, which helps keep nutrients intact while killing bacteria (without heat pasteurization).

Making cold-pressed vegetable juice at home? You don't have the option of industrial pascalization, so you need to be extra careful. Bacteria found on the outside of vegetables can end up in your cup, so clean produce well. Throw away any unused refrigerated juice after two or three days, because it contains no preservatives. Juice enthusiasts recommend drinking it right away for maximum nutrient value.

A note of caution: Excessive juice consumption can pose special dangers to people who are on blood thinners or have kidney disease, because high intakes of certain vitamins and minerals may interfere with medical conditions. Speak to your doctor before consuming a lot of juice, no matter what kind.

Finally, regardless of which juice you choose, ignore the marketing hype. Juice will not detox your body, boost your immune system or cure cancer. There's no scientific evidence that juice is any better than eating fruit or vegetables. Though a bit of juice can be part of a healthy diet, you can save money and time in the kitchen - and reduce the risk of consuming too much sugar - by simply eating fruits and vegetables instead.

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This article was written by Cara Rosenbloom, special to The Washington Post.

Rosenbloom, a registered dietitian, is president of Words to Eat By, a nutrition communications company specializing in writing, nutrition education and recipe development. She is the co-author of "Nourish: Whole Food Recipes Featuring Seeds, Nuts and Beans."