You are what you eat as they say. The nutritional profile of your food; the soil that your vegetables are grown or the feed that chickens, pigs, or cows consume really affects this profile and by extension your health. The following is an article from John Brady at the Menuism blog on the difference between grass fed beef and animals raised in factory farms.
"it’s common knowledge that most feedlot beef cattle are fed low doses of antibiotics to keep them from getting sick on their totally un-natural diet of grains and poor living conditions. What are the health risks for human consumption of this meat? What’s the broad picture of animal health in a CAFO? How does this relate to health benefits of grass-finished beef?" - Read more at: Menuism Blog