Are fresh juice drinks as healthy as they seem?

On these midsummer days, it's hard to walk down the street without passing someone sipping a vividly colored beverage. According to food industry statistics, these folks aren't likely to be drinking McDonald's Shamrock Shakes or 7-Eleven Slurpees. Instead, people are shifting from sugary beverages with artificial ingredients to cold-pressed juices and smoothies. Sales of juice extractors and blenders lead the small-appliance market, and juice bars continue to spring up on city streets, in shopping malls, and even in supermarkets.

There are a couple of reasons people are taking to these beverages, says Kathy McManus, director of the Department of Nutrition at Harvard-affiliated Brigham and Women's Hospital. "They think they are doing something healthy, and the beverages can be time savers. It can be faster to grab a smoothie in the morning instead of sitting down to breakfast."

What is cold-pressed juice?

Cold pressing employs the same principle as the hand-crank citrus juicer your mother or grandmother might have used: the fruits or vegetables are squeezed between two metal plates to extract the juice. Modern juice extractors may chop or grind the produce before applying hydraulic pressure to separate the juice from the pulp.

• The upsides: Because cold-pressed juices are usually served fresh, they retain more of a fruit's or vegetable's vitamins and minerals. They don't have the added sugars or artificial sweeteners that most bottled juices contain. Additionally, when a glass of juice is squeezed from several fruits or vegetables, it is likely to have a wider array of nutrients per ounce than a single piece of fruit.
• The downsides: Juice has less fiber than a whole fruit or vegetable does, and fruit juices in particular are likely to have a higher glycemic index — a measure of how a food raises blood-sugar levels — than a whole fruit. Also, "there's increasing evidence that drinking isn't as satiating as eating whole foods," says McManus. Studies indicate that people who drink juices tend to add them to their diets rather than substitute them for other foods, thus increasing their total calorie consumption.

What are smoothies?

Smoothies are usually concoctions of several of the following: pureed fruits, pureed vegetables, juices, dairy products, almond milk, coconut milk, soy milk, herbs, and spices. The nutritional and calorie content of the beverage can vary widely according to the ingredients.

• The upsides: "Smoothies can be a good way of getting vegetables if you're struggling to add them to your diet," McManus says. If you aren't crazy about leafy greens, blending them with berries or a ripe peach can disguise the taste of the vegetables. A smoothie can also provide a quick meal when you don't have time to cook or even prepare a salad. For example, throwing a handful of spinach, a cup of blueberries, a couple of frozen strawberries, and a cup of nonfat plain Greek yogurt in the blender can deliver a healthy meal or snack in a minute. And smoothies have a nutritional advantage over juices — because the whole fruit or vegetable is used, they have more fiber and a lower glycemic index.
• The downsides: If you're not careful, smoothies can pack in the calories. If you're ordering a smoothie at a juice bar or restaurant, ask if it contains added sugar, syrup, or honey. If you're blending your own, avoid fruit-flavored yogurts or frozen yogurts, which are likely to contain fruit syrups, added sugars, or artificial sweeteners. Use bananas, which have a high glycemic index, sparingly. Go lightly on the sweeteners; even "healthy" sweeteners like agave syrup and honey contain glucose.

The bottom line

Smoothies and cold-pressed juices may provide healthy snacks and an efficient way to get vegetables. But be sure to include the calories they provide in your daily calorie allowance. For a lower-calorie alternative the Harvard T.H. Chan School or Public Health has developed recipes for fruit coolers and flavored water.