Beyond the questions of environmental stewardship and moral/ethical reasons to eat organic, it is important to identify what sorts of nutrients that organic foods might contain in greater abundance and how this translates into better health. Vitamins aren’t the answer; simple enough to take a multivitamin pill and get what you need. A more promising possibility is antioxidants, nutrients such as the polyphenols that make red wine red and in general seem to be more prevalent in brightly colored foods. Antioxidants come in a variety of types, but in general they act as part of self-defense systems against spoilage and a number of environmental challenges. A well-know example is resveratrol from wine; this pluripotent polyphenol is an antiviral, antifungal, all-around good guy that seems to have a wide range of anti-aging properties. And because plants make these in response to environmental stress, they should make more of them when not pampered with sprays, fertilizers, and all manner of unnatural things, they should be more nutritious when left to fend for themselves. (A related concept is “biodynamic” farming.)
So a diet higher in antioxidants is a good thing. The science, however, is a bit trickier, since there are various ways of measuring antioxidant potency, and what works in the lab may not in the diet. Among the various ways to measure antioxidant potency is the ORAC test (Oxygen Radical Absoption Capacity), and it is possible to measure a sort of whole body ORAC with what is called “human plasma total antioxidant capacity.” The aforementioned study started by determining the ORAC levels of organic vs. traditionally farmed foods, including wine, and the scores were higher for the organic foods (with a few exceptions.) In test subjects converted to an organic Mediterranean diet, an increase of 21% in total body antioxidant capacity was seen after 14 days.
Does this mean your wines (and other foods) should be organic? You could make a case for it, but there are plenty of non-organically grown wines that pack a healthy punch. Winemakers already intentionally stress the vines in specific ways because more polyphenols also means more flavorful and distinctive wines. It is just fortunate that good wines tend to be good for you too.