We all know by now that a diet high in red meat is just not good for us. So if you are going to indulge and eat a burger or a steak, go grass fed since grass fed beef is better for you.
According to recent studies, grass fed cattle produce meat higher in beta carotene, vitamin E and omega-3 fatty acids than meat produced from cattle raised by conventional ranching techniques. This is not that surprising to me since conventional ranching techniques means cows raised in lots and fed mostly corn and processed feed. Now from what I have read in Michale Pollan's superbly written, highly informative book The Omnivore's Dilemma, cows evolved to eat grass and roam around in pastures. When cows eat grass they are leaner animals and produce leaner meat, which translates into healthier protein for us. Corn creates fat marbled meat that has become familiar as modern beef, but the corn also upsets the cows four stomachs. Which in turn, leaves cattle more prone to infections, hence the increase in antibiotics given to cows. Historically speaking, corn was not the major feed for cows until after WW II, which is relatively recent in the grand scheme of things.
Unfortunately, the label/term grass fed is not currently regulated by the USDA. Ranchers and farmers raising grass fed animals are lobbying hard to have the term regulated. So your best bet is finding a ranch close by that raises grass fed cattle. If you are interested in finding grass fed beef produced close to you - check out Local Harvest. The website has a great search feature so you can find grass fed meat and organic produce raised in your area. You can also find restaurants that serve it!!!