Daley CA, Abbott A, Doyle PS, Nader GA, and Larson S. (2010). A review of fatty acid profiles and antioxidant content in grass-fed and grain-fed beef. Nutrition Journal 9: 10.
Many people wonder if grass-fed beef is more nutritional than conventionally raised, grain-fed beef. A recent paper in the Nutrition Journal addressed this issue and found considerable differences between grass-fed and grain-fed beef. The study compares the fatty acid composition and vitamin content from seven different breeds of grass-fed and grain-fed cattle, specifically comparing loin eye cuts.
The researchers find that grass-fed beef has a lower fat content among all breeds of cattle. On average, grass-fed beef had 37% less fat than grain-fed beef.
Of particular interest is the omega-6 to omega-3 fatty acid ratio in grass-fed versus grain-fed beef. As discussed in the previous post, this ratio is very important to human health. While the total amount of omega-6 is not significantly different in grass-fed versus grain-fed beef, there is a significant difference in the omega-3 content. Grass-fed beef has much more omega-3 than grain-fed beef, resulting in grass-fed beef having a much more favorable omega-6 to omega-3 ratio. The average omega-6 to omega-3 ratio for grass-fed beef is 2.20, while the average omega-6 to omega-3 ratio for grain-fed beef is 7.66.
Another key difference is the amount of conjugated linoleic acid (CLA) present in the meat. CLAs are a group polyunsaturated fatty acids that have been shown to have a variety of health benefits including reduction in carcinogenesis, atherosclerosis, and diabetes (Scimeca and Thompson 1994, Kritchevsky et al 2000, Steinhart et al 1996). In addition, CLA has been shown to reduce the amount of body fat storage in a variety of animals and humans (Dugan et al 1999, Park et al 1997, Sisk et al 2001, Smedman and Vessby 2001). On average, grass-fed beef has 53% more CLA than grain-fed beef.
Grass-fed and grain-fed beef also differ in their β-carotene content. β-carotene is a precursor for vitamin A and is converted to vitamin A in the body. It is involved in vision, bone growth, reproduction, cell division and cell differentiation. It is produced by plants and when cattle eat fresh grass they store β-carotene in their fat. On average, grass-fed beef contains 900% more β-carotene than grain-fed beef.
α-tocopherol is a form of vitamin E and a powerful antioxidant. Antioxidants help protect cells against free radical damage, which can contribute to heart disease and cancer (Daley et al, 2010). On average, grass-fed beef contains 266% more α-tocopherol than grain-fed beef.
In summation, this study gives credence to the idea that our health depends not just on what we eat, but also on what the animals we are eating ate. The study indicates that grass-fed beef is more nutritious than grain-fed beef.
References:
Dugan MER, Aalhus JL, Jeremiah LE, Kramer JKG, Schaefer AL: The effects of feeding conjugated linoleic acid on subsequent port quality. Canadian Journal of Animal Science 1999, 79:45-51.
Kritchevsky D, Tepper SA, Wright S, Tso P, Czarnecki SK: Influence of conjugated linoleic acid (CLA) on establishment and progression of atherosclerosis in rabbits. Journal American Collection of Nutrition 2000, 19(4):472S-7S.
Park Y, Albright KJ, Liu W, Storkson JM, Cook ME, Pariza MW: Effect of conjugated linoleic acid on body composition in mice. Lipids 1997, 32:853-8.
Scimeca JA, Thompson HJ: Conjugated linoleic acid. Cancer Supplement 1994, 74(3):1050-4.
Sisk M, Hausman D, Martin R, Azain M: Dietary conjugated linoleic acid reduces adiposity in lean but not obese Zucker rats. Journal of Nutrition 2001, 131:1668-74.
Smedman A, Vessby B: Conjugated linoleic acid supplementation in humans – Metabolic effects. Journal of Nutrition 2001, 36:773-81.
Steinhart H, Rickert R, Winkler K: Identification and analysis of conjugated linoleic acid isomers (CLA). European Journal of Medicine 1996, 20(8):370-2.
