There isn’t just water and some grape ferment (alcohol) in a glass of wine. Depending on the type and the location grown, the nutritional value of wine offers plenty of health benefits. 
The polyphenols in red wine are phytochemicals with well-researched potentially positive nuances on cardiovascular health.
From them, resveratrol in particular also has anti-ageing quality due to its antioxidant prowess and other unknown mechanisms. Some studies are included bellow, but the researchers generally warn that no conclusions in terms of increased wine consumption can be drawn from their results.

  • Diabetes II sufferers marked improved structure of the aorta after consuming resveratrol (this human study used: 100-300mg daily for four weeks).
  • A clinical human trial with high-dose resveratrol found potential improvement of the progression in the Alzheimer disease.
  • Resveratrol activates proteins called sirtuins, the same proteins activated by caloric restriction, and “studies with animals found that most age-related diseases—including Alzheimer’s—can be prevented or delayed by long-term caloric restriction (consuming two-thirds the normal caloric intake)” and in this study patients taking resveratrol experienced weight loss. BUT!!! in the Alzheimer study, where participants lost weight “The highest dose of resveratrol tested was one gram by mouth twice daily — equivalent to the amount found in about 1,000 bottles of red wine.” I am introducing this point here to illustrate caution with any sensational findings published in wine magazines.

Next to the controversial findings with resveratrol, wine also contains some MINERALS such as calcium, iron, magnesium, phosphorus, potassium, sodium, zinc, copper, manganese, fluoride and selenium
and VITAMINS such as Thiamin, Riboflavin, Niacin, Panthotenic Acid and more. These micronutrients were all proven to benefit humans, showing that there is some nutritional value of wine.
For quantities and other nutritional information in your glass of red look at this table.
Nutritional value of wine is less marked in white wine, which contains less micronutrients than red, unfortunately. Check the nutritional break out here.
Apart from the physical aspects of wine drinking, the relaxing, calming effect of sipping wine moderately can benefit many with an inclination to stress, anxiety and other psychological disturbances. Still beware, wine is not a solution to your problems. As with any alcoholic beverage, it is not an enemy if you have a balanced, social relationship with consuming wine and basically anything moderately.