Low in fat and calories, fresh grapes contribute fiber, vitamins and minerals to your diet. European-style grapes may be either red or light green. This group includes the popular seedless green Thompson grape, the best-selling grape in the United States, the Iowa State University Extension program reports. American grapes are also called "slipskin grapes," because the outer layer is much looser than those of the European types. The dark blue Concord grapes, which contain seeds, are a classic American grape variety.
Vitamins and Minerals
European grapes offer 10 milligrams of vitamin C and 14 micrograms of vitamin K in each 1-cup serving. They also contribute 191 mg of potassium per serving, the United States Department of Agriculture calculates. American grapes, meanwhile, contribute 4 mg of vitamin C per cup, and, like European grapes, American varieties have 14 micrograms of vitamin K and 191 mg of potassium per cup.
Significance
Vitamin C helps strengthen blood vessels, bones and joints. An antioxidant vitamin, C is a key nutrient for boosting immunity, notes Oregon State University's Linus Pauling Institute, adding that men and women should consume about 60 mg daily. Vitamin K promotes healthy blood clotting, which is particularly useful for women with heavy menstrual cycle. It also fights bone loss and bone fragility leading to fractures. Adults need between 90 and 120 micrograms per day. Potassium helps promote healthy muscle and nerve function, and regulates your electrolyte balance. Adults should aim for 4700 mg of potassium daily, the Pauling Institute reports.
Flavonoids
Grapes, particularly red varieties, are rich in flavonoids. Flavonoids boast antioxidant and other healing properties, which help protect your body from heart disease and blood clots. One flavonoid, resveratrol, may have anti-cancer properties, according to the Iowa State University Extension. Both American and European red grapes, as well as hybrids of the two, are high in resveratrol. Grape juice and grape supplements represent a good way to get concentrated doses of resveratrol and other flavonoids, the extension program advises; however, you should check with your doctor before adding any supplements to your diet.
Additional Facts
All grapes are good fiber sources, notes the Iowa State University Extension. European grapes have 69 calories and 18 g of carbohydrates per 1-cup serving, the USDA reports. American grapes, meanwhile, contain 67 calories and 17 g of carbohydrates per cup. European and American grapes have virtually no fat or dietary cholesterol.
Considerations
A University of Michigan Cardiovascular Center study which showed grapes to lower blood pressure and improve heart function in animal testing used a mix of red, green and black grapes, the EurekAlert! website reported in 2009. Although red grapes are highest in the anti-cancer agent resveratrol, other beneficial compounds appear to be present in grapes of all pigments. The researchers theorized that a diet rich in grapes actually "turns on" genes in the heart responsible for producing glutathione --- a naturally occurring protein which helps protect the heart from oxidant stress caused by high blood pressure.
References
- U.S. Department of Agriculture: Recipe Tips: Grapes, American Type (Slip Skin), Raw
- U.S. Department of Agriculture: Recipe Tips: Grapes, Red or Green (European Type, Such as Thompson Seedless), Raw
- Oregon State University --- Linus Pauling Institute: Vitamins
- Oregon State University --- Linus Pauling Institute: Minerals
- EuekaAlert!: Benefit of Grapes May be More than Skin Deep
- Iowa State University Extension: Food of the Week: Grapes
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