Red or green grapes are healthy fruits. No problems to eat if you are healthy. But if you have diabetes, then you must reduce the amount drastically – allowed is only 2 to 5 pieces.
The nutrients in 100 g edible grapes include:

• Water – 81.1 g
• Protein – 0.7 g
• Fat – 0.3 g
• Carbohydrates – 15.2 g
• Organic acids 0.4 g – Malic acid 325 mg, Citric acid 25 mg, oxalic acid 8 mg, tartaric acid 530 mg, salicylic acid 1.4 mg
• Fibre – 1.6 g
• Minerals - 0.5 g – sodium 2 mg, potassium 195 mg, magnesium 8 mg, calcium 12 mg, iron 415 micro g, copper 95 micro g, zinc 50 micro g, selenium 2 micro g, iodide 1 micro g.
• Vitamins - vitamins A, B1, B6, nicotine amide, pantothenic acid, Biotin, folic acid, vitamin C – 4 mg, vitamins E, and K
• Purine – 25 mg

Grapes have many anti-oxidants and phyto-chemicals. Wine is one of the most consumed alcoholic drinks in the world. But, one glass is good to reduce the blood pressure. Large consumption increases the blood pressure because the blood vessels are narrowed from more alcohol. The dose makes the poison.

Resveratrol, the red substance from red grapes could reduce cholesterol.

Minerals, particularly selenium varies with their concentration in the soil.