Friday, June 10, 2016

A review of fatty acid profiles and antioxidant content in grass-fed and grain-fed beef

There is considerable support among the nutritional communities for the diet-heart (lipid) hypothesis, the idea that an imbalance of dietary cholesterol and fats are the primary cause of atherosclerosis and cardiovascular disease (CVD) []. Health professionals world-wide recommend a reduction in the overall consumption of SFAs, trans-fatty acids (TAs) and cholesterol, while emphasizing the need to increase intake of n-3 polyunsaturated fats [,].
Such broad sweeping nutritional recommendations with regard to fat consumption are largely due to epidemiologic studies showing strong positive correlations between intake of SFA and the incidence of CVD, a condition believed to result from the concomitant rise in serum low-density-lipoprotein (LDL) cholesterol as SFA intake increases [
,]. For example, it is generally accepted that for every 1% increase in energy from SFA, LDL cholesterol levels reportedly increase by 1.3 to 1.7 mg/dL (0.034 to 0.044 mmol/L) [-].

Beyond changes in genetics, some producers have also altered their feeding practices whereby reducing or eliminating grain from the ruminant diet, producing a product referred to as "grass-fed" or "grass-finished".
Historically, most of the beef produced until the 1940's was from cattle finished on grass. During the 1950's, considerable research was done to improve the efficiency of beef production, giving birth to the feedlot industry where high energy grains are fed to cattle as means to decrease days on feed and improve marbling (intramuscular fat: IMF).
In addition, U.S. consumers have grown accustomed to the taste of grain-fed beef, generally preferring the flavor and overall palatability afforded by the higher energy grain ration[
]. However, changes in consumer demand, coupled with new research on the effect of feed on nutrient content, have a number of producers returning to the pastoral approach to beef production despite the inherent inefficiencies.
Research spanning three decades suggests that grass-only diets can significantly alter the fatty acid composition and improve the overall antioxidant content of beef. It is the intent of this review, to synthesize and summarize the information currently available to substantiate an enhanced nutrient claim for grass-fed beef products as well as to discuss the effects these specific nutrients have on human health.