Recent studies have underscored the large difference in carotenoid content between grass-fed and conventionally fed beef. Grass-fed beef may contain more than twice the amount of beta-carotene and lutein that is present in conventionally fed beef. This relationship appears to hold true even if the cows have been fed silage during the winter months and pasture-feed only during the summer. In addition, some researchers have suggested that the yellowish color of fat in grass-fed beef is a good way to determine the extent to which the animals have been pasture-fed. 

The cholesterol content of grass-fed beef has repeated been shown to be lower than the cholesterol content in beef from conventionally fed animals. The decrease in cholesterol that you are most likely to obtain when switching from conventionally fed to grass-fed beef is approximately 22–39%. Since a single 4-ounce serving of conventionally fed beef will typically provide you with 90 milligrams of cholesterol or more, and since the recommended limit from the American Heart Association is 300 milligrams per day (and only 200 milligrams if you are a person who has experienced heart disease or has an LDL cholesterol of 100 mg/dL or more), this 22-39% decrease in cholesterol from grass-fed beef could be very helpful to you in helping you keep your total cholesterol intake under the recommended limit.

You'll find yourself getting 500-800 milligrams of CLA (conjugated linoleic acid) from a 4-ounce serving of grass-fed beef. This amount is approximately two to three times greater than the amount found in non grass-fed beef. CLA is a fatty acid made from linoleic acid, an omega-6 fatty acid commonly found in food. However, CLA is unique in its chemical structure, and this uniqueness is associated with an increasing list of health benefits, including immune and inflammatory system support, improved bone mass, improved blood sugar regulation, reduced body fat, reduced risk of heart attack, and maintenance of lean body mass. Grass-fed beef also contains greater amounts of vaccenic acid than conventionally fed beef. Various bacteria in our digestive tract are able to convert vaccenic acid into CLA once we've consumed grass-fed beef, and this process can further increase the practical amount of CLA that we receive from grass-fed animals.

The omega-3 fat content of grass-fed beef varies widely, due to the wide variety of forage crops that can be planted in pastures (or that grow on pastureland in the wild); the age, breed, and health of cows; and seasonal plant cycles in pastureland. Some recent studies show up to 3.5 grams of total omega-3 fats in 4 ounces of grass-fed beef. That level would provide you with 100% of the daily requirement. In other recent studies, total omega-3s in grass-fed beef only reached 1 gram. Still, a single gram of omega-3s could make an important contribution to a person's health. Most of the omega-3 content of grass-fed beef comes in the form of alpha-linolenic acid, or ALA. However, grass-fed beef also typically contains small-to-moderate amounts of other omega-3s, including EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). The range we've seen in recent studies is 20-720 milligrams for EPA, and 10-120 milligrams for DHA. In all cases described above, grass-fed beef contained greater amounts of omega-3s (for ALA, EPA, and DHA) than conventionally fed beef.

Broad-Based Nutrient Support

A recent study of children and teens in the U.S. has shown that individuals in these age groups depend on their intake of beef for the following key nutrients and in the following amounts.

• Vitamin B12: beef provides 14-21% of this B vitamin to U.S. children and teenagers
• Zinc: 13-19% of this mineral is provided by beef to these age groups
• Vitamin B3: U.S. children and teens receive 6-10% of their vitamin B3 from beef
• Vitamin B6: 5-8% of this vitamin is provided by beef to these age groups
• Iron: up to 8% of dietary iron is provided to these age groups by beef

Additionally, beef is an important source of potassium, phosphorus, and protein to these age groups in the U.S. population. Very few U.S. children and teenagers—and equally few U.S. adults—consume grass-fed versus conventionally fed beef. For this reason, we do not have data showing the potential contribution of grass-fed beef to other categories of nutrient consumption. However, we do have research evidence about the average composition of grass-fed versus conventionally fed beef, and this research evidence points to significant differences for the following key nutrients.

• Vitamin E: repeatedly show to be higher in grass-fed beef, sometimes at a level that is three times higher than conventional feeding
• Beta-carotene: shown in several studies to be significantly higher in grass-fed beef, and often at levels twice as high as the amount found in conventionally fed beef. Beta-carotene is not the only carotenoid phytonutrient that increases with grass feeding. The carotenoid lutein increases as well. This relationship between grass feeding and carotenoids appears to hold true even if the cows have been fed silage during the winter months and are pasture-fed only during summer months. The relationship between beta-carotene and grass-feeding in beef is so strong that some researchers have suggested that the yellowish color of fat in grass-fed beef can be used as a good way to determine the extent to which animals have been pasture-fed.
• Omega-3 fatty acids: because many forage plants contain the omega-3 fatty acid alpha-linolenic acid (ALA), cows that forage in a pasture typically get higher levels of ALA in their diet. This ALA gets passed on to us when we eat beef, drink milk, or consume dairy products from cows like cheese or yogurt. The omega-3 fat content of grass-fed beef varies widely due to the wide variety of forage crops that can be planted in pastures (or that grow on pastureland in the wild); the age, breed, and health of cows; and seasonal plant cycles in pastureland. Some recent studies show up to 3.5 grams of total omega-3 fats in 4 ounces of grass-fed beef. That level would provide you with 100% of the daily requirement. In other recent studies, total omega-3s in grass-fed beef only reached 1 gram. Still, a single gram of omega-3s could make an important contribution to a person's health. Since ALA is the most common omega-3 fatty acid in the plants that cows eat on pastureland, most of the omega-3 content of grass-fed beef comes in the form of ALA. However, just like humans, cows are capable of taking the ALA in their diet and converting some of it into other omega-3 fats, including EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). The range we've seen in recent studies for EPA and DHA in grass-fed beef is 20-720 milligrams for EPA and 10-120 milligrams for DHA. While the lower end of these ranges is relatively small (and far lower, for example, than the amount of EPA and DHA contained in many fish), it is still significant from a health standpoint. Additionally, in all of the research that we have reviewed, grass-fed beef has contained greater amounts of omega-3s than conventionally fed beef.
  
  

When combined with the B vitamins and minerals listed above, these additional nutrients specifically associated with grass-feeding of beef—including vitamin E, beta-carotene, and omega-3s—make grass-fed beef unusually diverse in terms of its potential for nutrient support of health. Our food rating system also ranks grass-fed beef as a very good source of the antioxidant mineral selenium and a good source of the B-vitamin choline.

Immune and Inflammatory Support

We have yet to see large-scale human studies showing decreased risk of chronic immune and inflammatory health problems following routine intake of grass-fed beef. Future results along these lines would not surprise us, since grass-fed beef can provide substantial amounts of the antioxidant vitamins E and beta-carotene, the antioxidant minerals selenium and zinc, and the anti-inflammatory fatty acid CLA. (For the cows themselves, research studies have already shown greater antioxidant capacity in their cells brought about by grass-feeding, as well as stronger performance of antioxidant enzymes like superoxide dismutase. In fact, grass feeding of cows has been shown to do a better job of increasing their antioxidant capacity than supplying them with antioxidant supplements.) Exactly how much these results will extend to humans will most likely depend on the role played by grass-fed beef in the overall diet. While rich in the potential for anti-oxidant and anti-inflammatory support, grass-fed beef also harbors the potential for excessive intake of nutrients like saturated fat and cholesterol when consumed in excessive amounts. It's exactly for this reason that we've recommended avoidance of large portions of grass-fed beef in your everyday meal (along the lines of a 12-ounce steak in the center of your plate that would be providing over half of the calories in your meal). Instead, we recommend an average serving size for grass-fed beef of approximately 4 ounces, whether added to a salad, stir-fry, sauce or other recipe.

Source: The World Healthiest  What's New and Beneficial About Grass Fed Beef