There are lots of reasons why feeding cattle grass rather than grain is better for the animals and the environment. But it’s also important for your health. First we’d like to acknowledge the excellent website www.eatwild.com for the information below. It has lots more, and we suggest you check it out. Google “grass-fed beef” to find several other good websites.
Total Fat and Calories
Beef from pasture-fed cattle has a lower fat content and has less calories than beef from grain-fed cattle. If the meat is very lean, it can have one third as much fat as a similar cut from a grain-fed animal. As you can see by the graph below, grass-fed beef can have the same amount of fat as skinless chicken, wild deer, or elk. Research also shows that lean beef actually lowers your “bad” LDL cholesterol levels.
Data from J. Animal Sci 80(5):1202-11.
Meat from grass-fed animals has two to four times more omega-3 fatty acids than meat from grain- fed animals. Omega-3s are called “good fats” because they play a vital role in every cell and system in your body. Of all the fats, they are the most heart-friendly. People who have ample amounts of omega-3s in their diet are less likely to have high blood pressure or an irregular heartbeat. Remarkably, they are 50 percent less likely to suffer a heart attack. Omega-3s are essential for your brain as well. People with a diet rich in omega-3s are less likely to suffer from depression, schizophrenia, attention deficit disorder (hyperactivity), or Alzheimer’s disease.
Another benefit of omega-3s is that they may reduce your risk of cancer. In animal studies, these essential fats have slowed the growth of a wide array of cancers and also kept them from spreading. Although the human research is in its infancy, researchers have shown that omega-3s can slow or even reverse the extreme weight loss that accompanies advanced cancer and also hasten recovery from surgery.[6,7]
Omega-3s are most abundant in seafood and certain nuts and seeds but they are also found in animals raised on pasture. The reason is simple. Omega-3s are formed in the chloroplasts of green leaves and algae. Sixty percent of the fatty acids in grass are omega-3s. When cattle are taken off omega-3 rich grass and shipped to a feedlot to be fattened on omega-3 poor grain, they begin losing their store of this beneficial fat. Each day that an animal spends in the feedlot, or fed grain in the paddock, its supply of omega-3s is diminished. The graph below illustrates this steady decline.
Data from: J Animal Sci (1993) 71(8):2079-88.
Conjugated Linoleic Acid (CLA)
Meat and dairy products from grass-fed ruminants are the richest known source of another type of good fat called “conjugated linoleic acid” or CLA. When ruminants are raised on fresh pasture alone, their products contain from three to five times more CLA than products from animals fed conventional diets. (A steak from the most marbled grass-fed animals will have the most CLA ,as much of the CLA is stored in fat cells.)
CLA may be one of our most potent defences against cancer. In laboratory animals, a very small percentage of CLA-a mere 0.1 percent of total calories-greatly reduced tumour growth.  There is new evidence that CLA may also reduce cancer risk in humans. In a Finnish study, women who had the highest levels of CLA in their diet, had a 60 percent lower risk of breast cancer than those with the lowest levels. Switching from grain-fed to grass-fed meat and dairy products places women in this lowest risk category.
In addition to being higher in omega-3s and CLA, meat from grass-fed animals is also higher in vitamin E. The graph below shows vitamin E levels in meat from: 1) feedlot cattle, 2) feedlot cattle given high doses of synthetic vitamin E (1,000 IU per day), and 3) cattle raised on fresh pasture with no added supplements. The meat from the pastured cattle is four times higher in vitamin E than the meat from the feedlot cattle and, interestingly, almost twice as high as the meat from the feedlot cattle given vitamin E supplements.  In humans, vitamin E is linked with a lower risk of heart disease and cancer. This potent antioxidant may also have anti-aging properties.
Data from: Smith, G.C. “Dietary supplementation of vitamin E to cattle to improve shelf life and case life of beef for domestic and international markets.” Colorado State University, Fort Collins, Colorado 80523-1171.
Grass-fed meat has a similar fat profile to wild game
When cattle are free to forage on their natural diet of grass, their meat is almost as lean as wild game. The graph below shows that grass-fed beef has an overall fat content similar to wild animals such as deer.
This second graph shows that grain-fed beef has a much higher ratio of omega-6 to omega-3 fatty acids than wild game or grass-fed beef. A high ratio of omega-6 to omega-3 fatty acids has been linked with an increased risk of cancer, cardiovascular disease, allergies, depression, obesity, and auto-immune disorders. (Simopoulos and Robinson, The Omega Diet, published by HarperCollins in 1999.) A ratio of four or lower is considered ideal. The ratio in grain-fed beef is more than 14 to 1. In grass-fed beef, it is approximately two to one.
Data for both graphs comes from G.J. Miller, “Lipids in Wild Ruminant Animals and Steers.” J. of Food Quality, 9:331-343, 1986.
1. Rule, D. C., K. S. Brought on, S. M. Shellito, and G. Maiorano. “Comparison of Muscle Fatty Acid Profiles and Cholesterol Concentrations of Bison, Beef Cattle, Elk, and Chicken.” J Anim Sci 80, no. 5 (2002): 1202-11.
2. Davidson, M. H., D. Hunninghake, et al. (1999). “Comparison of the effects of lean red meat vs lean white meat on serum lipid levels among free-living persons with hypercholesterolemia: a long-term, randomized clinical trial.” Arch Intern Med 159(12): 1331-8. The conclusion of this study: “…diets containing primarily lean red meat or lean white meat produced similar reductions in LDL cholesterol and elevations in HDL cholesterol, which were maintained throughout the 36 weeks of treatment.”
3. Siscovick, D. S., T. E. Raghunathan, et al. (1995). “Dietary Intake and Cell Membrane Levels of Long-Chain n-3 Polyunsaturated Fatty Acids and the Risk of Primary Cardiac Arrest.” JAMA 274(17): 1363-1367.
4. Simopolous, A. P. and Jo Robinson (1999). The Omega Diet. New York, HarperCollins. My previous book, a collaboration with Dr. Artemis P. Simopoulos, devotes an entire chapter to the vital role that omega-3s play in brain function.
5. Rose, D. P., J. M. Connolly, et al. (1995). “Influence of Diets Containing Eicosapentaenoic or Docasahexaenoic Acid on Growth and Metastasis of Breast Cancer Cells in Nude Mice.” Journal of the National Cancer Institute 87(8): 587-92.
6. Tisdale, M. J. (1999). “Wasting in cancer.” J Nutr 129(1S Suppl): 243S-246S.
7. Tashiro, T., H. Yamamori, et al. (1998). “n-3 versus n-6 polyunsaturated fatty acids in critical illness.” Nutrition 14(6): 551-3.
8. Duckett, S. K., D. G. Wagner, et al. (1993). “Effects of time on feed on beef nutrient composition.” J Anim Sci 71(8): 2079-88.
9. Dhiman, T. R., G. R. Anand, et al. (1999). “Conjugated linoleic acid content of milk from cows fed different diets.” J Dairy Sci 82(10): 2146-56. Interestingly, when the pasture was machine-harvested and then fed to the animals as hay, the cows produced far less CLA than when they were grazing on that pasture, even though the hay was made from the very same grass. The fat that the animals use to produce CLA is oxidized during the wilting, drying process. For maximum CLA, animals need to be grazing living pasture.
10. Ip, C, J.A. Scimeca, et al. (1994) “Conjugated linoleic acid. A powerful anti-carcinogen from animal fat sources.” p. 1053. Cancer 74(3 suppl):1050-4.
11. Aro, A., S. Mannisto, I. Salminen, M. L. Ovaskainen, V. Kataja, and M. Uusitupa. “Inverse Association between Dietary and Serum Conjugated Linoleic Acid and Risk of Breast Cancer in Postmenopausal Women.” Nutr Cancer 38, no. 2 (2000): 151-7.
12. Smith, G.C. “Dietary supplementation of vitamin E to cattle to improve shelf life and case life of beef for domestic and international markets.” Colorado State University, Fort Collins, Colorado 80523-1171