For many people, healthy food is about two things: nutrition and safety. In both these areas, organic food can be seen as a sensible choice. Studies have found significant areas where organic is superior to conventional in nutritional terms: An increasing body of evidence is pointing to organic food's benefits when it comes to those harder-to-find secondary nutrients in particular. While it is not the case that all relevant state authorities promote organic as more nutritious than conventional, there is ample evidence to suggest that it is.
The trend that appears to be emerging from the science is that while all food will give you the basic stuff you need, like protein, organic is a good way to access those harder to get micronutrients, useful for optimum health, like certain antioxidants.
You could say that organic is 'ahead of the curve' when it comes to safety. Organic food standards already disallow all synthetic pesticides which are, in more and more research, being shown to be of concern. As the years pass, synthetic pesticides banned under the organic system are banned from farming and growing in general. DDT and paraquat are perhaps the most famous, but others are added to the list of whats not allowed at regular intervals.
Nitrites/Nitrates in food are also emerging as a real area of concern. Because organic farmers do not apply synthetic nitrogen fertilizers, nitrite levels in organic foods tend to be lower. Lairon (2009), in a meta analysis of the available research, found nitrite levels in organic vegetables to be a full 50% lower. Nitrites/Nitrates are associated with increased risk of gastrointestinal cancer in adults.
It is also important to remember that studies have shown that soils are being depleted because of conventional farming practices: we need healthy soils to continue to have health food and thus healthy people.
Longitudinal studies also show that many foods are less nutritious than they were in the recent past. Davis et al (2004) covering the period from 1950-1999, tested 43 garden crops, and found that there was a statistically significant decline in 6 of 13 nutrients tested for: protein, calcium phosphorus, iron, riboflavin and ascorbic acid. The researchers concluded that “trade-offs between yield and nutrient content” may explain their findings.