When people eat grapes, they often eat the skinless white grapes whole, but for other types of grapes, they spit out the skin because it has a bitter taste. However, from a nutritional perspective, you should not spit out the grape skin when eating grapes.
The grape skin is rich in a polyhydroxy phenolic compound—resveratrol, which has effects such as lowering blood lipids, preventing thrombosis, preventing arteriosclerosis, and enhancing immune function.
Another important substance in grape skin—tannin, has effects such as anti-allergy, anti-aging, enhancing immunity, and preventing cardiovascular and cerebrovascular diseases.
The anthocyanin contained in grape skin has strong antioxidant, anti-mutagenic, liver function reducing, and cardiovascular protecting functions.
Grape skin also has anti-cancer effects. Researchers from the University of Illinois College of Pharmacy in the United States have found that this substance exists in varying amounts in more than 70 plants, such as peanuts and grapes, with the highest concentrations being in grape skins and red wine.
Because most grapes on the market currently have pesticide residue issues, they must be thoroughly cleaned before eating them with the skin. It is best to rinse them with water and use an effective detergent to clean the pesticides for more than two minutes. However, soaking in plain water or salt water is not recommended, as water immersion can easily promote the penetration of residual pesticides on the grape surface into the pulp.