Grassfarming and Human Nutrition by Jo Robinson; from her website www.eatwild.com
As you will see, products from pastured animals are ideal for human health. Very similar to wild game, they contain the amounts and kinds of nutrients that our bodies "expect"  to be fed. The research suggests that switching to grassfed products  could reduce the risk of diabetes, obesity, cardiovascular disease, and even cancer!
Products from pastured animals are better for your health in a number of important ways. First of all, they are lower in total fat than the meat from animals fattened in a feedlot. For     example, a sirloin steak from a grassfed steer has about one half to one third as much fat as a similar cut from a grainfed steer. In fact,  grassfed meat has about the same fat content as skinless chicken or wild deer or elk.1 When meat is this lean, it actually  lowers your LDL cholesterol  levels.2
Because grassfed meat is so lean, it is also lower in  calories. (Fat has 9 calories per gram, compared with only 4 calories for protein and carbohydrates. The greater the fat content, the greater the number of calories. A 6-ounce steak from a  grass-finished steer has almost 100 fewer calories than a 6-ounce steak  from a grainfed steer. If you eat a typical amount of beef (66.5 pounds a year), switching to grassfed beef will save you 17,733 calories a year without requiring any willpower or change in eating habits. If  everything else in your diet remains constant, you'll lose about six  pounds a year. If all Americans switched to grassfed meat, our  national epidemic of obesity might begin to diminish.
Extra Omega-3s
Although grassfed meat is low in total fat and "bad" fat (including saturated fat), it has two to six times more omega-3 fatty acids. Omega-3s play a vital role in every cell and system in your body.  For example, 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.3

Omega-3s are essential for your brain as well.  People with a diet rich in omega-3s are less likely to be afflicted with depression, schizophrenia, attention deficit disorder  (hyperactivity) or Alzheimer's disease.
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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.5 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 They may also enhance the response to chemotherapy.8
Omega-3s are most abundant in seafood and certain nuts and seeds such as flaxseeds and walnuts, 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 grain, they begin losing their store of this beneficial fat.  Each day that an animal spends in the feedlot, its supply of omega-3s is diminished.9 The graph below illustrates this rapid decline.
(Data from Duckett, S. K., D. G. Wagner, L. D. Yates, H.        G. Dolezal, and S. G. May. "Effects of Time on Feed on Beef Nutrient        Composition." J Anim Sci 71, no. 8 (1993): 2079-88.
When chickens are housed indoors and deprived of greens,  their meat and eggs also become artificially low in omega-3s. Eggs from pastured hens can contain as much as 20 times more omega-3s than eggs from factory hens.10
Switching our livestock from grass to grain is one of the reasons our modern diet is deficient in these essential fats. It has been estimated that only 40 percent of Americans consume a sufficient supply of these nutrients. Twenty percent have levels so low that they cannot be detected.11 Switching to grassfed animal products is one way to restore this vital nutrient to your diet.

The CLA  Bonus
Meat and dairy products from grassfed 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.12
CLA may be one of our most potent defenses against cancer. In laboratory animals, a very small percentage of CLA --- a mere 0.1 percent of total calories ---greatly reduced tumor     growth.13 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 grainfed to grassfed meat and dairy products places women in this lowest risk category.14 Researcher Tilak Dhiman from Utah State University estimates that you may be able to lower your risk of cancer simply by eating the following grassfed products each day: one glass of whole milk, one ounce of cheese, and one serving of meat. You would have to eat five times that amount of grainfed meat and dairy products to get the same level of protection.
Vitamin E
In addition to being higher in omega-3s and CLA, meat from grassfed 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.15 In humans, vitamin E is linked with a lower risk of heart disease and cancer. This potent antioxidant may  also have anti-aging properties. Most Americans are deficient in vitamin
References
1. Fukumoto, G. K., Y.S. Kim, D. Oduda, H. Ako (1995). "Chemical  composition and shear force requirement of loin eye muscle of young, forage-fed steers."  Research Extension Series 161: 1-5. Koizumi, I.,   Y. Suzuki, et al. (1991). "Studies on the fatty acid composition of  intramuscular lipids of cattle, pigs and birds." J Nutr Sci Vitaminol  (Tokyo) 37(6):  545-54.
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. Bougnoux, P., E. Germain, et al. (1999).   "Cytotoxic drugs efficacy correlates with adipose tissue docosahexaenoic        acid level in locally advanced breast carcinoma [In Process Citation]." Br J Cancer 79(11-12): 1765-9.
9. 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.
10.. Lopez-Bote, C.  J., R.Sanz Arias, A.I. Rey, A. Castano, B. Isabel, J. Thos (1998). "Effect of free-range feeding on omega-3 fatty acids and alpha-tocopherol content and oxidative stability of eggs." Animal Feed Science and Technology 72:33-40.
11. Dolecek, T. A. and G. Grandits (1991). "Dietary Polyunsaturated Fatty Acids and Mortality in the Multiple Risk Factor Intervention Trial (MRFIT)." World Rev Nutr Diet 66: 205-16.
12. 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.
13 . 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.
14. 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.
15.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
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