Effects of grass-feeding on the nutrient composition of beef

Just finished reading an article review by Lauren Gwin & Fred Martz on the effects of conventional and grass-feeding systems on the nutrient composition of beef. This review was based on an article by Leheska and published in Journal of Animal Science 86:3575-3585. The authors took ground beef and strip steaks from 15 grassfed beef producers from 13 different states on 3 different occasions. They were compared against grain fed beef from retail meat cases or university meat labs in 3 different regions on 3 different occasions. This paper contradicted prior data showing that grass-fed beef was lower in saturated fats and higher in monosaturated fats than grain fed beef. It also showed that grass-fed beef was leaner, had higher levels of Vitamin A and stearic acid which does not raise cholesterol in humans and may explain why the consumption of grass-fed beef tends to lower blood cholesterol.



Grassfed beef also had higher levels of conjugated linoleic acid (CLA), omega 3 fats, and trans-vaccenic acid.



These reviewers felt that the data was biased toward grain fed beef because the samples of grain fed beef were on grain for an unspecified period of time. Beef on grain for more than 100 days will have a higher saturated fatty acid concentration than cattle on grain for less than 100 days. Since most beef consumed from retailers has been grain fed for more than 100 days the saturated fatty acid content tends to be higher. Thus if the cattle grain fed beef studies was on grain for less than 100 days, the fatty acid content may not have reflected what most consumers eat from retail grocers. One also wonders that in order to get published in this peer review journal the reviewers might have suggested toning down the grass-fed rhetoric in order to stay in line with conventional wisdom and grain fed dogma.