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First the Facts
In my lecture circuit this question is common (especially in the Northwest). At this time there is no known nutritional benefit to eating organically grown food versus conventionally grown, and because of that our position is that eating organic or not is your decision, but you should know the facts. If you eat "organic" to improve health, that probably won't happen. If you are doing it to help the environment, that makes sense. 

Many people can't afford to purchase all their groceries certified organic, as there is a significant cost increase over conventional foods. And on that note, the certified organic production of food is not a financially feasible option to feed our entire population and never will be unless it becomes the same cost or less than our current methods of mass food production. So it's your choice. If you can afford it there is a case to be made for environmental protection, including supporting a more sustainable agricultural system that better protects the land and workers, and possibly taste (or not depending on growing factors - see below) or freshness, but not for improving health or longevity. BUT that's not to say that if we could improve the environment enough, it may eventually help us live longer. The key word here is enough. Again, we would never be able to feed the masses if we reached the level of “organic” food production needed to have a significant impact on de-polluting our world. No one could bear that cost in today’s economics – and in our capitalistic societies, where competition is fierce and the driving force behind all methods of food production, don’t expect to undo that process anytime soon. But hey, let's keep the pressure on.

Certified Organic Facts
Natural foods, organic or not, will always vary
All natural foods, whether produced organically or conventionally, will vary in their composition of nutrients and other nutritionally relevant substances, meaning a particular organic food may have less nutrient value and/or taste than a conventional counterpart and vice-versa. Different plants of the same crop may differ in nutrient composition, which can also vary depending on fertilizer and pesticide regimen, growing conditions, season, soil content, harvest times and other factors. The nutrient composition of livestock products can similarly be affected by factors such as the age and breed of the animal, feeding regimen, and season. This inherent variability in nutrient content may be further affected during the storage, transportation, and preparation of the foodstuffs before they reach the mouth of the consumer.

Certified organic means?
Unfortunately a 2005 court ruling banning 38 different synthetic products used in standard organic farming was reversed by congress in 2006. So yes, there are still a lot of synthesized materials/chemicals used in certified organic farming, but it's still a more environmentally friendly method of food production as described below.
USDA certified organic foods are grown and processed according to federal guidelines addressing, among other factors, soil quality, animal raising practices, pest and weed control, and use of additives. Organic producers rely as much as possible on natural substances and physical, mechanical, or biologically based farming methods. All organic agricultural farms and products must meet the following USDA monitored guidelines:
  • Abstain from application of prohibited materials (including synthetic fertilizers, pesticides, and sewage sludge) for 3 years prior to certification and then continually throughout their organic license
  • Prohibit use of genetically modified organisms and irradiation
  • Incorporate positive soil building, conservation, manure management and crop rotation practices
  • Provide outdoor access and pasture for livestock
  • Refrain from antibiotic and hormone use in animals
  • Animals diets must be 100% organic feed
  • Avoid contamination during the processing of organic products
  • Maintain records of all operations
Most reliable studies have found no nutrient benefits with organic foods
Organic options have no special nutrient-content benefits, according to a sweeping new review of the scientific literature. Commissioned by Britain’s Food Standards Agency, the study by researchers at the London School of Hygiene & Tropical Medicine looked at 162 scientific papers published over the past 50 years. The conclusion is a disappointment to organic food fans: “Our review indicates that there is currently no evidence to support the selection of organically over conventionally produced foods on the basis of nutritional superiority.” Also however, organically produced foods are not inferior to their conventional counterpart.

 Environmental benefits
There may be many but to name a few: reduction in pesticides uses/residues, soil nitrates, working conditions, animal treatment, potentially improved human immune systems, less by-products from synthesized material manufacturing, etc.