Studies of forage and/or grass feeding of cattle versus grain finishing have been conducted in varying regions throughout the world but generalization of these results to beef from U.S. cattle may not be appropriate. In particular, available grass/forage variety and form as well as cattle breed have a significant impact on the nutritional profile of beef. The current review summarizes the nutritional characteristics of beef as reported from the limited number of studies comparing U.S. grass/forage-fed versus grain-finished cattle and estimates the intake of key nutrients that might be expected from consumption of U.S. beef from either feeding system. In addition, many studies report changes in fatty acids solely as a percentage of total fatty acids. Since grass/forage feeding typically results in a leaner product; the current review compares the fatty acid profile of beef from grass/forage feeding to that of grain-finished cattle on a mg/100 g of meat basis.

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Dietary patterns are an important concept in dietary recommendations. The Western pattern is most commonly defined as a diet characterized by high intakes of refined grains, sugar and red meat, and has been shown to be associated with increased risks for certain types of cancer, coronary heart disease, diabetes, and obesity. However, isolating the independent effects of individual foods on health outcomes is central to helping individuals choose foods to build healthier dietary patterns to which they can adhere. Red meat is a popular source of high quality protein and provides a variety of essential nutrients that improve overall diet quality. It is also a source of saturated fatty acids, which observational evidence suggests are associated with heart disease, although recent data challenge this. Several studies have shown that lean red meat can be successfully included in recommended heart-healthy dietary patterns without detriment to blood lipids. Furthermore, increased dietary protein has been shown to promote healthy body weight and composition, in part by increasing satiety, and to improve vitality and stamina.

Meat is a food for humans. However, beef consumption in the United States has steadily declined by >14% over the past decade due to a variety of factors, including insufficient knowledge of animal protein. This study quantified all proteinogenic AA as well as nutritionally and physiologically significant nonproteinogenic AA and small peptides in beef cuts from 3 subprimals (chuck, round, and loin). Beef carcasses ( = 10) were selected at 3 commercial packing plants in the United States. Retail-cut samples were analyzed for the nitrogenous substances after acid, alkaline, or enzymatic hydrolysis and after deproteinization. In these chuck, round, and loin cuts, total amounts of glutamate (free plus peptide bound) were the highest (69-75 mg/g dry weight) followed by lysine, leucine, arginine, and glutamine in descending order. This is the first study to determine aspartate, asparagine, glutamate, and glutamine in meat proteins of any animal species. In all the beef samples evaluated, glutamine was the most abundant free AA (4.0-5.7 mg/g dry weight) followed by taurine, alanine, glutamate, and β-alanine. Additionally, samples from all beef cuts had high concentrations of anserine, carnosine, and glutathione, which were 2.8 to 3.7, 15.2 to 24.2, and 0.68 to 0.79 mg/g dry weight, respectively. Beef top loin steaks appear to provide higher protein nutrition values than top round steaks and under blade roasts, but all are excellent sources of proteinogenic AA as well as antioxidant AA and peptides to improve human growth, development, and health. Our findings may help guide future decisions regarding human and animal nutrition.

A systematic review was used to identify randomized controlled trials (RCTs) and observational epidemiologic studies (OBSs) that examined protein intake consistent with either the US RDA (0.8 g/kg or 10–15% of energy) or a higher protein intake (≥20% but <35% of energy or ≥10% higher than a comparison intake) and reported measures of kidney function. Studies (n = 26) of healthy, free-living adults (>18 y old) with or without metabolic disease risk factors were included. Studies of subjects with overt disease, such as chronic kidney, end-stage renal disease, cancer, or organ transplant, were excluded. The most commonly reported variable was glomerular filtration rate (GFR), with 13 RCTs comparing GFRs obtained with normal and higher protein intakes. Most (n = 8), but not all (n = 5), RCTs reported significantly higher GFRs in response to increased protein intake, and all rates were consistent with normal kidney function in healthy adults. The evidence from the current review is limited and inconsistent with regard to the role of protein intake and the risk of kidney stones. Increased protein intake had little or no effect on blood markers of kidney function. Evidence reported here suggests that protein intake above the US RDA has no adverse effect on blood pressure. All included studies were of moderate to high risk of bias and, with the exception of 2 included cohorts, were limited in duration (i.e. <6 mo). Data in the current review are insufficient to determine if increased protein intake from a particular source, i.e., plant or animal, influences kidney health outcomes. These data further indicate that, at least in the short term, higher protein intake within the range of recommended intakes for protein is consistent with normal kidney function in healthy individuals.

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