Protein is a major source of energy in the human diet, accounting for 10-20% of all calories consumed. Adequate dietary protein intake is critical for the maintenance of normal body function. Protein serves many purposes and is needed for the growth, maintenance and repair of all cells in the body. Protein is a building block for muscle, organs and other vital tissues throughout the body. Finally, protein serves to aid metabolism, digestion and the transport of nutrients and oxygen in the bloodstream.
The Dietary Reference Intake for protein set forth by the United States Department of Agriculture (USDA) is to eat 0.8 grams of protein for every kilogram of body weight. This works out to about 36 grams of protein per day for every 100 pounds of weight. Therefore, a 200-pound person needs to eat about 72 grams of protein each day.
One of the best sources of protein in the diet is beef. Depending on the cut, a 3-ounce serving of beef contains 20-25 grams of protein. Furthermore, the protein in beef is “complete protein”, which means it contains all of the amino acids needed for the body to make muscle tissue, hormones, red blood cells and other substances. In contrast, incomplete proteins contain some amino acids, but the missing amino acids must be eaten from other food sources in order to form a complete protein. Although beef is a rich source of complete proteins in the diet, it should be consumed in moderation, since eating too much protein from animal sources may increase the amount of cholesterol and triglycerides in the bloodstream.
Not all beef has the same nutritional profile. The cattle used to produce beef have traditionally been fed diets of grain. However, many farms are switching from grain-fed to grass-fed beef because of the numerous proven benefits to human health.
Overall, grass-fed cattle are healthier than grain-fed cattle. The livers of grain-fed cattle have a 30-fold increase in abscesses, 8-fold more blood vessel disorders and a 3-fold greater frequency of liver contamination (Roberts 1982). Many clinical studies have compared the nutritional content of grass-fed to grain-fed beef. Beef from grass-fed cattle has been shown to have better overall quality in terms of color, lipid oxidation and alpha-tocopherol levels than beef from maize-fed cattle (O’Sullivan 2002). This study found that maize-fed beef had the poorest color while grass-fed beef had the best. Lipid oxidation, which has negative impact on beef flavor, color, and nutritional value, was highest in maize-fed beef and lowest in grass-fed beef. Alpha-tocopherol concentrations (the form of whole food vitamin E that is preferentially absorbed in humans) were also highest in grass-fed beef and lowest in maize-fed beef.
The amount and types of fat contained in grass-fed beef are also superior. Concentrations of alpha-linolenic acid (ALA), an essential fatty acid, were greatest in the grass-fed beef and lowest in maize-fed beef. Numerous other studies have confirmed the superior fatty acid profile of grass-fed beef, including higher levels of conjugated linoleic acid (CLA), another type of healthy fat, vaccenic acid, a naturally-occurring fatty acid with distinct health benefits, omega 3 fatty acids, an unsaturated fat that reduces coronary heart disease risk and lower levels of total fat, saturated fat and trans fat (Hebeisen 1993, Leheska 2008, Ponnampalam 2006). Grass-fed beef also has twice the amount of beta-carotene as grain-fed beef. When consumed, beta-carotene is converted to vitamin A in the body, where it helps to maintain normal vision, reproductive function and bone health.
Based on these research findings, there are numerous health benefits to be enjoyed from regularly consuming grass-fed beef. The USDA reports that the average American consumes 67 pounds of beef each year (Davis 2005). Because of the lower fat content and therefore fewer calories in grass-fed beef, switching from grain-fed to grass-fed beef can result in 6 pounds of fat loss per year, with no other changes in diet or activity levels.
Consumption of essential fatty acids, especially omega-3 fatty acids lowers blood pressure and reduces the risk for heart disease, cancer, mental disorders and autoimmune diseases. Vitamin E is a potent antioxidant and helps to lower heart disease and cancer risk and has anti-aging properties. High CLA intake lowers cancer risk due to its strong antioxidant properties and may lower body fat levels, especially in the abdomen. Beta-carotene, another antioxidant, serves to protect against tumor growth and cancer risk. Diets low in saturated and trans-fats can reduce total cholesterol and LDL cholesterol. Lower intake of these fats also reduces the risk for chronic diseases such as heart disease, blood vessel disease, cancer, diabetes and obesity.
Overall, numerous research studies have proven that grass-fed beef is the superior protein because it contains high levels of complete protein and, unlike grain-fed beef, contains antioxidants and healthy fatty acids that serve to protect against chronic disease. The natural phytonutrients rich diet of grass fed beef is definitely not withstanding.
Dr. Linda Kennedy MS SLP ND
Christopher G. Davis and Biing-Hwan Lin. Factors Affecting U.S. Beef Consumption. United States Department of Agriculture. 2005, http://www.ers.usda.gov/publications/ldp/Oct05/ldpm13502/ldpm13502.pdf
Hebeisen DF, Hoeflin F, Reusch HP, Junker E, Lauterburg BH. Increased concentrations of omega-3 fatty acids in milk and platelet rich plasma of grass-fed cows. Int J Vitam Nutr Res. 1993;63(3):229-33
Leheska JM, Thompson LD, Howe JC, Hentges E, Boyce J, Brooks JC, Shriver B, Hoover L, Miller MF. Effects of conventional and grass-feeding systems on the nutrient composition of beef. J Anim Sci. 2008 Dec;86(12):3575-85. Epub 2008 Jul 18
O'Sullivan A, O'Sullivan K, Galvin K, Moloney AP, Troy DJ, Kerry JP. Grass silage versus maize silage effects on retail packaged beef quality. J Anim Sci. 2002 Jun;80(6):1556-63
Ponnampalam EN, Mann NJ, Sinclair AJ. Effect of feeding systems on omega-3 fatty acids, conjugated linoleic acid and trans fatty acids in Australian beef cuts: potential impact on human health. Asia Pac J Clin Nutr. 2006;15(1):21-9
Roberts JL. The prevalence and economic significance of liver disorders and contamination in grain-fed and grass-fed cattle. Aust Vet J. 1982 Nov;59(5):129-32