Grapes and Their Juice May Offer Many Low-Calorie Benefits

Grapes have probably been around since prehistoric times. Native Americans, for example, had wild grapes growing along the banks of streams, but those grapes were very sour. When the Spanish settlers arrived in California, they brought sweeter varieties with them, and the offspring of those vines thrive to this day. Grapes are very adaptable and will grow in many climates. In fact, they grow on six continents.

Individual varieties of table grapes, which include seedless and seeded types, are harvested at different times of the year. Some of the most familiar names include the Black Beauty (late May to early July); Calmeria (January and February); Cardinal (May through mid-August); Champagne (September and October); Emperor (August through March); Flame Seedless (June through December); Thompson Seedless (June through November). The availability of some seasonal varieties is extended by imports from Mexico and Chile.

Grapes sweeten as long as they’re on the vine, but after they’ve been picked, the ripening process stops, so the timing of the harvest is very important. The process is still done largely by hand to protect the clusters.

Grapes haven’t got much to offer in the way of vitamins, minerals or even fiber, but they do contain a number of phytochemicals that are currently the subject of much research into their cholesterol-lowering effects and their overall heart-protective qualities.

It’s not yet known whether the same positive effects of moderate red-wine consumption can be obtained by drinking grape juice or eating grapes. Nonetheless, grapes are fairly low in calories (114 calories in a cup of grapes) and make a great snack or dessert. Though it might seem that red and purple grapes should be high in beta carotene, their color actually comes from pigments, not from any of the carotenoids. These pigments are also the subject of research into their possible health effects.

Grape juice is made by crushing the grapes (just as in the making of wine). Also like wine, juice gets its color from the skin, which is included in the processing. Concord grapes are the main variety used to make juice, which has an extremely high sugar content and therefore more calories than some other juices. For example, an 8-ounce glass of grape juice can have between 128 to 155 calories (depending on whether it is made from concentrate), compared with 100 calories for grapefruit juice and 110 for orange juice.

When you select grapes in the market, make sure that they are not displayed more than two bunches deep and are kept under refrigeration. They are easily damaged, and those packaged in plastic bags or tissue paper are better protected but harder to check before you buy them.

Most grapes are not picked until they are ripe, but the color can tell you a lot. Green grapes should be a kind of translucent yellow-green rather than opaque green. Red grapes should be a nice crimson color, and blue/black grapes should be almost black. Avoid any bunches with wrinkled, sticky or off-color grapes.

When you get grapes home, store them in the refrigerator in a perforated plastic bag. They should keep for about a week. Don’t wash them until you’re ready to serve them.

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Dr. Sheldon Margen is a professor of public health at UC Berkeley; Dale A. Ogar is managing editor of the UC Berkeley Wellness Letter. Send questions to Dale Ogar, School of Public Health, UC Berkeley, Berkeley, CA 94720-7360, or e-mail to daogar@wellnessletter.com.