A new study published in The Journal of Nutrition concluded that “ounce equivalents” of animal- and plant-based protein-rich foods may not be metabolically equivalent after all. Dietary protein is needed for the synthesis of the structural and functional components of living cells. Thus, food protein quantity and quality are both essential for good health. The Dietary Guidelines for Americans (DGAs) published an “ounce equivalents” recommendation to help consumers meet protein requirements with a variety of protein food sources. For example, the DGAs present a variety of “ounce equivalents” in the protein food groups stating that 1 ounce of meat is equivalent to 1 cooked egg, ¼ cup of red kidney beans, 1 tablespoon of peanut butter, 2 ounces of tofu, and 0.5 ounces of mixed nuts. However, the DGAs do not currently address the issue of differences in protein quality associated with varied food sources. In general, animal proteins have higher protein digestibility and a better essential amino acid profile relative to dietary requirements. These measures of protein quality indicate that animal proteins can more readily provide the daily requirement of essential amino acids than plant protein. To investigate the physiological response to various ounce equivalents of protein food sources, Robert Wolfe (University of Arkansas for Medical Sciences) and colleagues randomly assigned 56 young healthy adult participants to 1 of 7 food intervention groups: 2 ounces of cooked beef sirloin, 2 ounces of cooked pork loin, 2 cooked eggs, ½ cup of red kidney beans, 2 tablespoons of peanut butter, 4 ounces of tofu, or 1 ounce of mixed nuts. Prior to the onset of the study, participants followed a 3-day dietary weight maintenance. Participants’ net whole-body protein balance was assessed using a stable isotope tracer infusion protocol. The changes from baseline following consumption of the different protein food sources were compared with the baseline value for that individual. Consumption of ounce equivalents of animal-based protein food sources resulted in greater gain in whole-body net protein balance above baseline than the ounce equivalents of plant-based protein food sources. Overall, animal-based protein food sources elicited greater anabolic responses than plant-based protein food sources. The improvement in whole-body net protein balance was due to an increase in protein synthesis with all the animal protein sources. In addition, the egg and pork groups also suppressed protein breakdown compared with the plant protein sources. The magnitude of the whole-body net balance response was correlated with the essential amino acid content of the protein food source. The researchers concluded that “ounce equivalents” of protein food sources as expressed in the DGAs are not metabolically equivalent and this should be considered as the DGAs develop approaches to establish healthy eating patterns. A corresponding editorial by Glenda Courtney-Martin (University of Toronto) stresses the importance and timely contribution of this study, which could guide future decisions regarding how protein foods can be better categorized by the DGAs. References Park S, Church DD, Schutzler WE, Azhar G, Il-Young K, Ferrando AA, Wolfe RR. Metabolic Evaluation of the Dietary Guidelines’ Ounce Equivalents of Protein Food Sources in Young Adults: A Randomized Controlled Trial. The Journal of Nutrition, Volume 151, Issue 5, May 2021, Pages 1190–1196, https://doi.org/10.1093/jn/nxaa401. Courtney-Martin G. False equivalence or fake news: is a peanut really an egg? The Journal of Nutrition, Volume 151, Issue 5, May 2021, Pages 1055–1056, https://doi.org/10.1093/jn/nxab051. Images via canva.com. Dr. Kathy Beerman teaches in the School of Biological Sciences at Washington State University. The author of several published articles, she is interested in research that focuses on the efficacy of a novel approach to treating iron deficiency anemia in rural regions of Guatemala and Ecuador. Dr. Beerman teaches an undergraduate nutrition course for health majors, as well as a course that prepares students to participate in a 10-day medical mission to Guatemala. Since joining the faculty at Washington State University in 1990, she has been the recipient of several teaching awards (the Burlington Northern Faculty Meritorious Achievement in Teaching Award, the R.M. Wade Foundation Award for Excellence in Teaching, and the Sahlin Faculty Excellence Award for Instruction). More recently, she received the CAS Outstanding Achievement Award in International Activities (2017) and the President’s Award for Leadership (2018). Other scholarly activities include co-author of two introductory nutrition textbooks (Nutritional Sciences: From Fundamentals to Food and NUTR). Protein is an essential part of the diet. It helps to build, repair, and maintain the body’s structures. Foods derived from plants and animals can both provide protein, but there are some differences. Protein exists throughout the body, in everything from the muscles and organs to the bones, skin, and hair. The body does not store protein like it does other macronutrients, so this protein has to come from the diet. Proteins are made up of amino acids. A person’s body needs a balance of all 22 types of amino acids to function correctly. The body cannot produce nine of these acids, called essential amino acids. A complete protein source refers to a type of food that contains all nine. Having the right balance of amino acids can build muscle and help the body to recover from exercise quickly. Understanding the differences between plant and animal proteins is important for anyone who wants to ensure that their diet is healthful. In this article, we look at the differences between animal and plant proteins. We also investigate the effects on health, describe which type is better for bodybuilding, and list the best sources of each.
One of the main differences between plant and animal proteins involves their amino acid contents. Amino acids are the building blocks of protein. When the body digests the proteins in food, it breaks them down into amino acids. The body may need different amino acids at different times. Many people believe that the diet should include complete sources of protein, which contain all nine essential amino acids. Some animal products are complete sources of protein, such as:
Most plant proteins are incomplete, which means that they are missing at least one of the essential amino acids. However, some plant-based foods, such as quinoa and buckwheat, are complete sources of protein. It is important for vegetarians and vegans to mix their protein sources and ensure that they are getting all of the essential amino acids. Also, keep in mind that some sources of plant protein may take longer for the body to digest and use. The following are examples of plant-based foods rich in protein:
Many other nuts, grains, and vegetables also contain high amounts of protein. When choosing between plant and animal sources of protein, it is important to factor in the other nutrients that the foods provide. Foods rich in protein can have widely ranging nutritional profiles. Certain sources of animal protein can contain high levels of heme iron and vitamin B-12, while some plant-based foods lack these nutrients. On the other hand, plant-specific nutrients, called phytonutrients, and some antioxidants are absent from sources of animal protein. Animal products contain saturated fat and higher levels of cholesterol than sources of plant protein. A person may wish to avoid animal products for these reasons. Many used to believe that dietary cholesterol was associated with cardiovascular disease. While recent evidence suggests no significant link, the Institute of Medicine (IOM) still recommends limiting dietary cholesterol. Fiber is another important factor. Only plant-based foods contain fiber, which helps to keep the digestive system balanced. Eating more plant protein may also improve a person’s overall health. Results of a 2016 meta-analysis suggested that eating more animal protein, especially that derived from processed red meat, may increase the risk of dying from cardiovascular disease. However, researchers noted that they only found the link between animal protein and cardiovascular disease in people with at least one lifestyle-related risk factor, such as smoking, heavy alcohol intake, or being overweight or obese. The results also indicated that eating more plant protein may help to reduce this risk and others. In general, the best way to cover a person’s dietary needs is to eat a wide variety of foods. Athletes and others looking to increase muscle mass and reduce the amount of time it takes to recover from exercise often pay close attention to their protein intake. Protein helps repair and build up the muscles after a rigorous workout. Many athletes turn to whey protein for building muscle. This type of protein is easier for the body to break down and absorb, which can give whey an edge over other sources, such as meat, eggs, and vegetables. Regarding plant-based sources, one study suggests that that rice protein isolate may offer similar benefits to whey protein. Many people recommend consuming a combination of plant-derived proteins after a workout. This can provide the body with a range of amino acids. Simply getting enough protein in the diet may be more important than focusing on the kind of protein. One study found that including above-average levels of protein in the diet improved signs of muscle health, such as lean mass and strength in the quadriceps. The researchers noted that the amount of protein was more important than the type. However, some sources of protein may be better for general health. For example, fish and white meats tend to contain less fat than red meats. For many people, the choice between animal and plant proteins involves a range of considerations. Rather than focusing on a single type of protein, it may be better to focus on eating a wide variety of foods. This can help ensure that a person gets a healthful balance of amino acids and other vital nutrients. Anyone with specific questions about protein requirements and sources should speak with a dietitian. Last medically reviewed on August 21, 2018
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Why are animal proteins considered to be better than plant proteins
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