April 2019 Issue
Protein Myths & Facts
By Carrie Dennett, MPH, RDN, CD
Vol. 21, No. 4, P. 30
Setting the Record Straight on This Popular — but Misunderstood — Macronutrient
Protein: It’s an essential component of muscle, skin, hair, and nails, as well as antibodies, hormones, and cell structures. With confusion among consumers about how much carbohydrate and fat they should be eating, protein has emerged as the most popular macronutrient. In spite of that, protein still can be misunderstood.
But before exploring—and debunking—protein myths with your clients and patients, it might be worth double-checking whether they know what protein is.
“I’ve had so many clients over the years tell me that their main protein sources are the following: avocados, spinach, and kale,” says Mandy Enright, MS, RDN, RYT, creator of the couples nutrition blog Nutrition Nuptials (www.NutritionNuptials.com). “I typically give them a list of protein sources that indicate anything that comes from an animal, such as the meat itself or a product produced by the animal like dairy, cheese, and eggs. I also review common sources of plant-based protein including soy, beans, pulses, nuts, and seeds.”
Here are the top protein myths dietitians often hear from clients and consumers and the facts to set them straight.
Myth: Animal protein is more easily absorbed than plant protein.
Fact: The biological value of a protein generally is determined by its amino acid composition (essential vs nonessential, complete vs incomplete) and digestibility. Whether the protein is plant- or animal-based is less of a consideration, although that may play a role in how efficiently our bodies can extract the amino acids from the food’s overall “matrix.”1,2
The protein digestibility-corrected amino acid score (PDCAAS) is commonly used in the United States to assess protein quality, while the digestible indispensable amino acid score is supported by the Food and Agriculture Organization of the United Nations.2
In the PDCAAS, foods with lower levels of indispensable, or essential, amino acids—the amino acids you must get from food because your body can’t make them—are characterized as “lower-quality” protein.2 However, the PDCAAS and other measures of biological value don’t account for whether the food is raw or cooked and how it interacts with other protein-containing foods.1 As a result, many plant foods may have a lower value because they’re too low in an essential amino acid, something that may matter little in the context of a varied diet. Also worthy of consideration is that plant-based protein has benefits for the environment, plus it comes “packaged” with fiber, healthful polyunsaturated and monounsaturated fats, and phytochemicals.
The “bioavailability myth” is one that Vicki Shanta Retelny, RDN, a Chicago-based author, speaker, and culinary consultant (victoriashantaretelny.com), hears often. “I clear it up by saying that the amino acids in plants are just as bioavailable as animal proteins and it not only helps maintain muscle mass but keeps your bones healthy, too,” she says.
Research does suggest that plant proteins from whole plant foods are slightly less digestible (maybe 10% to 20%) than animal proteins due to the high fiber content interfering with absorption. Another potential concern is how much leucine—one of the branched-chain amino acids—is in a food. Leucine is critical for triggering new muscle protein synthesis,3,4 and animal proteins such as dairy, eggs, meat, and fish contain more leucine than plant-based proteins. What does this mean? It means we need to eat more plant-based protein to get adequate leucine.1,5 Of the plant-based proteins, soyfoods contain the most leucine.6
Myth: Vegetarians and vegans don’t get enough protein.
Fact: In developed countries, at least, vegetarians and vegans get enough protein—and enough leucine.1,7 This myth likely stems in part from the bioavailability myth but also from the common worry that plant proteins, unlike animal proteins, aren’t complete.
It’s true that most plant foods don’t contain high levels of all nine of the essential amino acids—soy, quinoa, and buckwheat do, but most plant foods are lacking in either lysine or methionine. However, we now know that we don’t need to get all nine essential amino acids from the same food, and we don’t need to combine different plant foods, such as grains and beans, to form a “complete protein” in the same meal. Eating a variety of protein-rich plant foods in the course of your day provides enough protein and easily fills in any amino acid gaps.8
“Plant-based folks can easily meet their protein needs through soyfoods, beans and lentils, and nuts and seeds. Whole grains and veggies also contain protein,” says Seattle-based Ginger Hultin, MS, RDN, CSO, a spokesperson for the Academy of Nutrition and Dietetics and owner of www.champagnenutrition.com. “Just like an omnivorous diet, include a protein source at all meals and snacks. Try a tofu scramble for breakfast, some nut butter on whole grain toast, chia seed pudding, or hot quinoa with walnuts to start your day off right.”
California-based Jessica Gust, MS, RDN, owner of www.elementnutritionco.com, works with kids and families and frequently hears parents say that their child isn’t eating “enough” meat and thus isn’t getting enough protein. “They get concerned so they want to know about protein powder for their kids, which I don’t really recommend,” she says. “I usually will do a full intake assessment and find they are getting more than enough protein from milk and other dairy, beans and lentils, some meats, and peanut butter, plus a variety of other grains they eat. People are surprised to hear how much protein their kids are actually eating.”
New York–based Lisa Young, PhD, RDN, CDN, author of Finally Full, Finally Slim, says many of her clients think that if they move toward more plant-based eating, they will be lacking protein. “Clearly, that’s not the case,” she says. “I discuss healthful veggie and plant-based proteins including legumes, nuts, seeds, and tempeh.”
Myth: Daily protein needs for healthy adults are only 46 g for women and 56 g for men, and most Americans get too much protein.
Fact: According to the 2015–2020 Dietary Guidelines for Americans, while it’s true that many (60%) Americans exceed their recommendations for protein intake, based on servings, a significant percentage (40%) falls short.9 And, as dietitians know, the recommended protein intake isn’t the same number for everyone.
Unlike micronutrients, protein needs aren’t determined by age and gender—body weight matters. The Recommended Dietary Allowance (RDA) of 0.8 g/kg of body weight per day makes the 46 g appropriate for a 126-lb woman and the 56 g appropriate for a 154-lb man. Plus, research is increasingly finding that the term “adequate” isn’t the same as “optimal”—the RDA is defined as the level of protein required to offset deficiency in 98% of people but may do little to help maintain or build muscle mass.10
Considering that adults lose about 3% to 8% of muscle mass per decade after age 30, a rate that increases after age 60,11 countering that loss through appropriate physical activity and optimal protein intake is important to preserve muscle mass and prevent age-related declines in health and physical functioning, especially since older adults need more protein to stimulate muscle synthesis.12,13
Many researchers say that 1 to 1.2 g/kg per body weight per day is a more optimal intake, with room to go higher.3,10 In meal terms, for many adults this means aiming for at least 25 to 30 g protein per meal. This maximizes your body’s muscle repair and building machinery.5
In research studies, an uneven distribution of protein (too low at some meals, higher than necessary at others) is associated with frailty, slower walking speed, and fatigue.3,14
Myth: If more protein is good, then much more is better.
Fact: While getting enough protein is important for growth and maintenance of muscle and other tissues, what may not be ideal for health and the environment, according to a substantial body of research, is consuming excess animal protein.15,16 There’s evidence that a higher-protein diet can aid in weight loss and prevention of weight gain, especially when combined with physical activity, by increasing satiety and postmeal thermogenesis, but “high” protein isn’t as high as many consumers may think.
Several studies use a diet that provides 25% of calories from protein, compared with a “standard” research diet of 12% protein.5 This is still far below the 40% protein recommended by many commercial diet programs and diet books, but much higher than the RDA.
Cincinnati-based Karolin Saweres, RDN, LD, founder of www.mynutritionandme.com, says one aspect of the “more is better” myth is that taking protein supplements is more beneficial for muscle growth—and the more expensive the better.
Speaking of protein supplements, Columbus, Ohio–based Ashley Koff, RD, CEO of thebetternutritionprogram.com, often hears the myth that collagen is a good protein choice. “In reality, if you swap out your protein for collagen, it could negatively impact serotonin by not getting enough tryptophan,” she says. “So if you want to add collagen, it would need to be in addition to meeting your daily protein needs from quality plants, and, if you choose, animal products.”
North Carolina–based Judith Scharman Draughon, MS, RDN, LD, author of Lean Body, Smart Life, frequently hears this related myth: Protein gives you energy.
“I help clients understand that protein is for maintaining and building muscles as well as replacing other needed protein in the body,” she says. “That gives me an opportunity to address another major protein misunderstanding: the need for healthful carbohydrates with protein to allow the protein to be used for protein and not be broken down for energy instead, since creating energy is the body’s first priority.”
Myth: Soy isn’t a safe protein.
Fact: The origins of this myth come from one of the phytochemical types in soy, isoflavones, which also are phytoestrogens—plant compounds that weakly mimic the effect of the hormone estrogen. While this once raised concerns that eating soy might increase breast cancer risk, the American Cancer Society says the evidence suggests that moderate intake of soyfoods is safe and possibly beneficial.17 When eaten regularly, isoflavones have been linked to lower risk of breast and prostate cancer, as well as heart disease, type 2 diabetes, and osteoporosis.18
“Soy unsafe for those with cancer? Soy not good for men? Children should avoid soy? No to all!” Hultin says. “Tofu, tempeh, miso, and edamame are fantastic protein sources that offer a variety of vitamins, minerals, and antioxidants that meat doesn’t. Soy is a critical protein for any vegetarian or vegan. Swap it into your diet as an omnivore, too, for a healthful alternative protein source.”
Myth: You can’t be vegan and lose weight because beans are too high in carbs.
Fact: While it’s true that beans and lentils are higher in carbohydrates than animal-based protein foods, observational studies—which can’t establish cause and effect—show that vegetarians and vegans tend to have a lower BMI than nonvegetarians and nonvegans.19
In addition, recent clinical research shows that, overall, no one macronutrient ratio is superior for weight loss or for health.20 Results from the DIETFITS study, which randomized 609 adults to a low-fat (average 29% fat) or low-carb (average 30% carb) diet, found no average difference in weight change between the groups, although there were dramatic interindividual differences in each group.21
Myth: Too much protein is bad for the bones and kidneys.
Fact: Lindsey Janeiro, RDN, CLT, founder of nutritiontofit.com, often hears that higher protein intake can cause osteoporosis. “More recent research disproves this, including a 2017 review from the National Osteoporosis Foundation, which concluded that current evidence shows no adverse effects of higher protein intake,” she says.22
Indeed, hypotheses from the 1920s about excess protein leaching calcium from bones have been disproven. While it’s true that calcium excretion increases as protein intake increases, so does calcium absorption, leading to no net loss in calcium. In addition, protein makes up about one-half of bone volume and one-third of its mass.22
Adequate—but not excessive—protein (0.8–1.5 g/kg/day) is particularly important for bone health in children and adolescents, as it provides a source of amino acids to build the bone matrix while also stimulating insulinlike growth factor 1, which is important for bone formation.23 In older people with osteoporosis, several studies have found that bone mineral density is higher when protein intake is more than 0.8 g/kg/day or is 24% of total energy intake.3
As for protein and kidney health, the National Kidney Foundation says protein isn’t “hard” on healthy kidneys, and that difficulties don’t develop until stage 4 or 5 of chronic kidney disease.24 A 2009 prospective study among healthy adults found no association between protein intake and decline in kidney function,25 while a 2019 review article also found no association between baseline protein intake and long-term kidney function decline in the general public or people with normal kidney function at baseline.26
Myth: It’s difficult to get enough protein at breakfast.
Fact: Breakfast is the meal where protein tends to be lowest, because foods such as oatmeal, cereal, and toast are relatively low in protein. But while it can feel challenging to meet protein needs at breakfast, it’s certainly not impossible. It’s also important, because the human body breaks down and rebuilds muscle throughout the day.
Research suggests that to maximize the body’s muscle repair and building machinery, after age 30 adults need to distribute protein intake fairly evenly across the day.3,5
The following are several dietitians’ favorite protein-rich breakfasts that are somewhat “out of the box”:
• Saweres says one of her favorite delicious breakfasts is fava beans with chopped fresh tomato, green onions, cumin, salt, and pepper.
• Lisa Andrews, MEd, RD, LD, owner of soundbitesnutrition.com, recommends adding a side of black or pinto beans to eggs. “They are really filling and provide a nice dose of protein and fiber to start the day,” she notes.
• Denver-based Jessica Crandall Snyder, RDN, CDE, AFAA, owner of www.vitalRD.com, also likes beans with eggs in the form of breakfast tacos, adding bell peppers and tomatoes, but her new favorite breakfasts are sweet potato hash with eggs and flavorful, nutrient-rich shakshuka—eggs baked in a spicy tomato-pepper sauce. She also recommends making breakfasts on Sundays for the week ahead. “The prep work is done and then you can ‘make time’ for fueling your body and metabolism before starting your day,” she says.
• South Carolina–based Jennifer Hunt, RDN, LD, owner of www.healthy-inspiration.com, likes to pour egg whites into hot cooked oatmeal or hot cereal. “It makes them light and fluffy with a boost of protein,” she says.
• Draughon likes adding cottage cheese to scrambled eggs to boost protein and keep them from drying out. “The cottage cheese really does make better eggs and you don’t know it’s there,” says Draughon, who also suggests mixing a couple of heaping spoonfuls of cottage cheese or plain Greek yogurt into a small container of sweetened Greek yogurt to boost protein while diluting the sugar. “Top with nuts, too, and you can pack close to 30 g of protein into a 5.3-oz cup of Greek yogurt on your way out the door.”
• Janeiro points out that breakfast doesn’t have to be traditional American breakfast foods. “There’s no reason why you can’t eat your leftover chicken or salmon from dinner last night for breakfast today,” she says. “In fact, that can save time in the morning and money, if it was something you otherwise would have tossed.”
• Gust says parents love her suggestion to make pancakes from banana, eggs, oats, and pumpkin spice—higher in protein and fiber than traditional pancakes without added sugars. Other winners are egg breakfast muffins—aka omelets in muffin tins—stirring peanut butter into hot cereal, and rolling fruit slices in chia, flax, or hemp seeds to provide “grip” and add some protein—great for babies and toddlers.
— Carrie Dennett, MPH, RDN, CD, is the nutrition columnist for The Seattle Times, owner of Nutrition By Carrie, and author of Healthy for Your Life: A Holistic Guide to Optimal Wellness.
1. Paddon-Jones D, Coss-Bu JA, Morris CR, Phillips SM, Wernerman J. Variation in protein origin and utilization: research and clinical application. Nutr Clin Pract. 2017;32(1_suppl):48S-57S.
2. Marinangeli CPF, House JD. Potential impact of the digestible indispensable amino acid score as a measure of protein quality on dietary regulations and health. Nutr Rev. 2017;75(8):658-667.
3. Bauer J, Biolo G, Cederholm T, et al. Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. J Am Med Dir Assoc. 2013;14(8):542-559.
4. Devries MC, McGlory C, Bolster DR, et al. Leucine, not total protein, content of a supplement is the primary determinant of muscle protein anabolic responses in healthy older women. J Nutr. 2018;148(7):1088-1095.
5. Arentson-Lantz E, Clairmont S, Paddon-Jones D, Tremblay A, Elango R. Protein: a nutrient in focus. Appl Physiol Nutr Metab. 2015;40(8):755-761.
6. van Vliet S, Burd NA, van Loon LJ. The skeletal muscle anabolic response to plant- versus animal-based protein consumption. J Nutr. 2015;145(9):1981-1991.
7. Sanders TA. The nutritional adequacy of plant-based diets. Proc Nutr Soc. 1999;58(2):265-269.
8. Marsh KA, Munn EA, Baines SK. Protein and vegetarian diets. Med J Aust. 2013;199(4 Suppl):S7-S10.
9. US Department of Health and Human Services. 2015–2020 Dietary Guidelines for Americans, 8th ed. Chapter 2: shifts needed to align with healthy eating patterns. https://health.gov/dietaryguidelines/2015/guidelines/chapter-2/current-eating-patterns-in-the-united-states/. Published January 7, 2016.
10. Phillips SM, Chevalier S, Leidy HJ. Protein “requirements” beyond the RDA: implications for optimizing health. Appl Physiol Nutr Metab. 2016;41(5):565-572.
11. Volpi E, Nazemi R, Fujita S. Muscle tissue changes with aging. Curr Opin Clin Nutr Metab Care. 2004;7(4):405-410.
12. Moore DR, Churchward-Venne TA, Witard O, et al. Protein ingestion to stimulate myofibrillar protein synthesis requires greater relative protein intakes in healthy older versus younger men. J Gerontol A Biol Sci Med Sci. 2015;70(1):57-62.
13. Wall BT, Cermak NM, van Loon LJ. Dietary protein considerations to support active aging. Sports Med. 2014;44(Suppl 2):S185-194.
14. Deutz NE, Bauer JM, Barazzoni R, et al. Protein intake and exercise for optimal muscle function with aging: recommendations from the ESPEN Expert Group. Clin Nutr. 2014;33(6):929-936.
15. van Nielen M, Feskens EJ, Mensink M, et al. Dietary protein intake and incidence of type 2 diabetes in Europe: the EPIC-InterAct Case-Cohort Study. Diabetes Care. 2014;37(7):1854-1862.
16. Levine ME, Suarez JA, Brandhorst S, et al. Low protein intake is associated with a major reduction in IGF-1, cancer, and overall mortality in the 65 and younger but not older population. Cell Metab. 2014;19(3):407-417.
17. ACS guidelines on nutrition and physical activity for cancer prevention: common questions about diet and cancer. American Cancer Society website. https://www.cancer.org/healthy/eat-healthy-get-active/acs-guidelines-nutrition-physical-activity-cancer-prevention/common-questions.html. Updated February 5, 2016.
18. Messina M. Soy and health update: evaluation of the clinical and epidemiologic literature. Nutrients. 2016;8(12):E754.
19. Farmer B. Nutritional adequacy of plant-based diets for weight management: observations from the NHANES. Am J Clin Nutr. 2014;100(Suppl 1):365S-368S.
20. Ludwig DS, Willett WC, Volek JS, Neuhouser ML. Dietary fat: from foe to friend? Science. 2018;362(6416):764-770.
21. Gardner CD, Trepanowski JF, Del Gobbo LC, et al. Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults and the association with genotype pattern or insulin secretion: the DIETFITS randomized clinical trial. JAMA. 2018;319(7):667-679.
22. Shams-White MM, Chung M, Du M, et al. Dietary protein and bone health: a systematic review and meta-analysis from the National Osteoporosis Foundation. Am J Clin Nutr. 2017;105(6):1528-1543.
23. Mitchell PJ, Cooper C, Dawson-Hughes B, Gordon CM, Rizzoli R. Life-course approach to nutrition. Osteoporos Int. 2015;26(12):2723-2742.
24. Is protein and phosphorus hard on kidneys? National Kidney Foundation website. https://www.kidney.org/blog/ask-doctor/protein-and-phosphorus-hard-kidneys. Published May 15, 2012.
25. Halbesma N, Bakker SJ, Jansen DF, et al. High protein intake associates with cardiovascular events but not with loss of renal function. J Am Soc Nephrol. 2009;20(8):1797-1804.
26. Bilancio G, Cavallo P, Ciacci C, Cirillo M. Dietary protein, kidney function and mortality: review of the evidence from epidemiological studies. Nutrients. 2019;11(1):E196.