But why is it better, and what does it actually mean? I'll quote a long passage from the book Anticancer, by David Servan-Schreiber (pg. 73). It's one of two books (along with Fat Chance by Robert H. Lustig M.D.) that I recommend to everyone - they will change the way you look at your diet, and help explain how closely related your diet and health really are. This passage looks at information regarding omega-3s, which are advertised everywhere, but rarely explained or understood. We accept that they're good, but have a hard time knowing why, or understanding how they end up in our foods.
"In the natural cycle, cows give birth in spring, when the grass is most luxuriant, and produce milk for several months until summer's end. Spring grass is an especially rich source of omega-3 fatty acids; these fatty acids are therefore concentrated in the milk from cows raised in pastures and in the milk's derivatives--butter, cream, yogurt, and cheese. Omega-3s are likewise found in beef from grass-fed cattle and in eggs from free-range chickens fed with forage (rather than grain).
Starting in the fifties, the demand for milk products and beef went up so much that farmers had to look for shortcuts in the natural cycle of milk production and reduce the grazing area needed to feed a 750-kilogram (1,600-pound) cow. Pastures were thus abandoned and replaced by battery farming. Corn, soy, and wheat, which have become the principal diet for cattle, contain practically no omega-3 fatty acids. To the contrary, these food sources are rich in omega-6s. Omega-3 and omega-6 fatty acids are called "essential" because the human body cannot make them. As a result, the quantity of omega-3s and omega-6s in our bodies stems directly from the content of the food we eat. In turn, the amounts of omega-3 and omega-6 fatty acids in our food depend on what the cows and chickens we eat have consumed in their feed. If they eat grass, then the meat, milk, and eggs they provide are perfectly balanced in omega-3s and omega-6s (a balance close to 1-1). If they eat corn and soy, the resulting imbalance in our bodies is as much as 1/15, even 1/40.
The omega-3s and omega-6s in our bodies constantly compete to control our body functions. Omega-6s help stock fat and promote rigidity in cells as well as coagulation and inflammation in response to outside aggression. They stimulate the production of fatty cells from birth onward. Omega-3s are involved in developing the nervous system, making cell membranes more flexible, and reducing inflammation. They also limit the production of adipose cells. Our physiological balance depends very much on the balance between omega-3s and omega-6s in our body, and therefore in our diet. It turns out that it is this dietary balance that has changed the most in the last fifty years."
Make the change today, and start eating grass-fed / free-range / local when possible.