Juices are excellent sources of nutrients and may help put the squeeze on various ailments: one 4-ounce (125-milliliter) glass of juice provides a full serving of fruits or vegetables and can therefore be part of a healthy diet. On the downside, juices lack the fiber of fresh fruits and vegetables and may contain heaping helpings of calories and natural sugars. Giving infants too much juice may increase their risk of tooth decay and even hamper normal development.
Most fruit and vegetable juices are good sources of potassium, which help regulate blood pressure. Many are also excellent sources of cancer-fighting antioxidants, including vitamin C. One 8-ounce (235-milliliter) glass of orange or grapefruit juice, fresh or from concentrate, supplies between 100 and 200 percent of the vitamin C recommended for all adults. Even juices that don’t naturally contain much vitamin C are often fortified with it. Apricot and mango juice are rich in both vitamin C and beta-carotene.
Citrus juices are also great sources of folic acid, a B vitamin that may help prevent heart disease and birth defects. Researchers also believe that folic acid – plentiful in orange juice – may help prevent breast cancer; studies are ongoing. You can now buy orange juice fortified with calcium – an option for adults who don’t get enough calcium from other sources.
Although some people choose to make their own juices, store-bought juices can be quite nutritious, too. Citrus juices are processed for shipment and brought to market so quickly that they retain most of their vitamins and minerals. However, as juice in a carton sits on the shelf, it loses nutrients as a result of oxidation. If the carton is near its "best before" date, pass it up.
If you’re watching your weight, remember that while vegetable juices tend to be fairly low in calories – an 8-ounce (235-milliliter) glass of tomato juice has only 43 – many popular fruit juices pack between 100 and 180. Drink several glasses a day, and the calories can add up. If you drink a lot of juice, consider diluting it with seltzer or water. And don’t forget to balance your juice intake with whole fruits and vegetables, which often have fewer calories. A glass of orange juice has 100 to 120 calories; a whole orange has only 60.
What’s more, unlike juices, whole fruits also supply fiber, which helps keep bowel movements regular, protect against cancer of the bowel, and prevent diabetes and heart disease. (One exception: prune juice contains much of the fiber, and the iron, found in prunes.) Fiber also helps you feel full.
Take precautions when giving fruit juice to children. Nutritionists often recommend that parents not give fruit juice to children under age one, and to limit children ages two to three to 4 to 8 ounces (125 to 235 milliliters) a day, preferably with meals. Drinking a lot of fruit juice may mean drinking less milk and even eating less food. In one study, small children who drank 12 to 30 ounces (350 to 890 milliliters) of fruit juice a day (25 to 60 percent of their total calorie intake) failed to grow and develop normally. Too much fruit juice, particularly apple juice, can also cause diarrhea. And never let your toddler fall asleep while drinking a juice (or milk) bottle: juice and milk sugars can cause cavities.
Of course, downing juice is infinitely preferable to drinking soda or coffee. But be sure to leave room for whole fruits and vegetables, too.