Eating moderate amounts of grass-fed meat for only four weeks will give you healthier levels of essential fats, according to a 2011 study in the British Journal of Nutrition -
The British research showed that healthy volunteers who ate grass-fed meat increased their blood levels of omega-3 fatty acids and decreased their level of pro-infalmmatory omega-6 fatty acids. These changes are linked with a lower risk of a host of disorders, including cancer, cardiovascular disease, depression and inflammatory Disease. Interestingly, volunteers who consumed conventional grain-fed meat ended up with lower levels of omega-3 and higher levels of omega-6s than they had at the beginning of the study, suggesting that eating conventional meat had been detrimental to their health.
From - British Journal of Nutrition (2011) Red meat from animals offered a grass diet increases plasma and platelet N-3 PUFA in Healthy consumers. Volume 105,pages 80-89.