Black grapes, velvety colored and deliciously sweet and juicy, can be consumed fresh and raw, dried as raisins or as a juice. Rich in nutrients, black seedless grapes are similar in taste and texture to red or green grapes, but because of their skin color, they have a higher antioxidant content. The U.S. Department of Agriculture recommends between 1 1/2 and 2 cups of fruit each day as part of a balanced diet, and eating black grapes will help you meet that goal.
Anthocyanins are the flavonoid compound that gives black grapes their dark color; the darker the fruit, the higher the anthocyanin content. A natural antioxidant, anthocyanins protect your body from damage from free radicals, produced as your body breaks down food, reducing the risk of cell damage and death and potentially slowing down the aging process. A study published in the 2010 "Annual Review of Food Science and Technology" found that anthocyanins may help reduce inflammation and cancer activity, alleviate diabetes and control obesity.
Polyphenols also are present in high concentrations in black grapes. One of the most widely found and consumed natural antioxidants, they occur mainly in fruits and plant-based drinks, including juices and red wine made from black grapes. A 2005 publication of the American Society for Clinical Nutrition cites polyphenols as preventing cardiovascular diseases, cancers and osteoporosis. They may also help prevent neurodegenerative diseases and certain types of diabetes. Most of the studies were in vitro or animal experiments, however, so the research isn't conclusive.
Low Glycemic Index
According to “A History of Food,” black grapes have a lower glycemic index than other grapes. While "Harvard Health Publications" cites the average GI for all grapes as 59, black grapes, according to “A History of Food,” have a GI of 43 to 53. The lower the GI is, the less effect the food has on your blood sugar and insulin levels. This means grapes won't cause your blood sugar levels to spike, which, in addition to being dangerous for diabetics, can lead to energy highs and crashes.
A phytonutrient, resveratrol is present in high concentrations in all grapes, including black grapes. A natural antioxidant, resveratrol may be useful in increasing lifespan and preventing the growth and development of cancer cells. But the majority of studies of the substance have been done on yeast, insects and animals, so the effect of resveratrol in humans isn't yet understood. Some scientists believe it may be the resveratrol content of red wine that makes the “French Paradox” possible -- low levels of cardiovascular disease among the French despite high levels of cigarette smoking and saturated fat in the typical French diet.