Beef from cows that feed on grass instead of grain in feedlots is healthier because it contains twice as much beta-carotene, has more vitamin E, and is lower in calories and saturated fat. Grass-fed animals are also known to be the richest source of one of the most potent cancer fighters - Conjugated Linoleic Acid, or CLA - a "good fat."
Recent research shows that grazing animals have from 3-5 times more CLA than animals fattened on grain in a feedlot, and studies published by the journal “Cancer Research” show that lab animals fed even very small amounts of CLA (less than 2 percent of total calories) reduced tumor growth by 60 percent.
Conjugated Linoleic Acid is a
Potent inhibitor of breast, prostate, lung, and colon carcinogenesis
Immune system enhancer
Anti-atherosclerotic and decreases LDL cholesterol
Substantial booster of Vitamin A in the liver
Inhibitor of diabetes
Modifier of the way the body metabolizes fat in such a way that body fat is significantly decreased while muscle mass is increased
What’s more amazing is that these effects are achieved at levels of about 1-2% of caloric intake - equivalent to about 2-3 grams daily of CLA for humans. Studies have shown no negative effects of taking CLA at these levels for extensive time periods, and recent reports have even demonstrated that CLA reduces body fat accumulation. However, since most of the research with CLA to date has been conducted on animals, often with relatively large doses, until human trials are conducted the exact dosage for humans is unknown.
More significant fat loss would occur if the dosage was closer to that used in animal studies, which would be equivalent to upwards of 25 g of CLA oil daily, but the risk of liver enlargement and insulin resistance would be proportionally increased, so this quantity is not recommended. It is wiser to use a lower dose of CLA in conjunction with other fat loss agents, and monitor glucose and insulin levels and liver parameters whenever possible.