The inability to retain muscle and strength associated with aging is called sarcopenia, and it is not only a concern for older adults. Loss of muscle mass begins to occur after the age of thirty at the rate of 1% per year [1], and the gradual inability to retain muscle mass and strength generally begins occurring by age fifty [2]. Muscle loss affects 5-13% of adults between the ages of sixty to seventy, and up to half of adults older than eighty years of age have sarcopenia [3].
Not being able to retain muscle mass results in older adults no longer being able to remain active, a reduced quality of life, osteoporosis, increased risk of falls, and a worsening of metabolic health [4].
Most people have never paid attention to the amount and quality of the protein they eat – choosing instead to select protein foods based on taste preference, economics, or ethical or religious reasons. These are all important considerations; however, they are not the only ones. As outlined in a previous article about the role of protein in the diet of older adults, high biological value protein that contain sufficient amounts of the amino acid leucine are necessary for the health of muscle [5], but in this regard not all protein foods are equal.
Amino acids are the building blocks of protein, including muscle, and there are twenty amino acids categorized into two groups: essential and non-essential amino acids. Essential amino acids, including leucine which is required for muscle growth and repair are not produced by the body in sufficient amounts. Leucine must be obtained through diet, which is what makes it an “essential” amino acid.
The leucine content of proteins is critical because leucine is what triggers mTOR signaling in muscle that stimulates muscle growth. For this reason, the proteins people need to contain sufficient leucine – especially older adults who want to retain muscle mass, and mobility.
Plant proteins generally contain lower levels of leucine compared to animal proteins [6]. Grains such as wheat contain less than 7% leucine [7] and even quinoa which is considered a “complete protein” because it has all essential amino acids only contain only 4.5% leucine [8]. People who want to eat a more plant-based diet to retain muscle may turn to legumes (“beans”) for protein, but they are usually incomplete proteins – meaning they are missing essential amino acids, and are generally poor sources of leucine. Even soybeans, which are complete proteins, contain only 8% leucine [9].
Dietary Recommendations for older adults emphasize a minimum of 20g of protein per meal, with more than 2.3 g leucine at each of 3 meals to ensure the building of new muscle protein [10].
Furthermore, to retain muscle and to recover the loss of muscle mass in older adults, the recommended intake of leucine is 3g per at each of 3 meals, along with 25-30g of protein [11].
Protein Sources to Help Retain Muscle
Animal proteins are highly bioavailable complete proteins and the richest sources of leucine. Only 1 cup of 1% fat cottage cheese contains 2.9g of leucine per cup – the amount needed for an entire meal! A cup of plain yogurt contains 1.3g of leucine, and a cup of Greek yogurt contains 1.2 g of leucine. Only 3 oz. of ground beef or pork contains 1.8g of leucine and the same amount of chicken breast contains 2.25g – all the leucine that is needed in a meal [11]. These are excellent protein and leucine containing food to help retain muscle.
Soybeans which are a complete plant-based protein contain only 0.28g leucine per half cup, and firm tofu which is a concentrated form of soy protein has between 0.73g of leucine for three ounces, so to get sufficient leucine from firm tofu would require an older adult to eat ¾ of a pound – well beyond the appetite of many older adults. Incomplete proteins such as lentils have only 0.7g of leucine per half cup, and black beans only 0.61g leucine per half cup – so for an older adult to get the minimum amount of leucine at a meal (2.3 g leucine) from either of these, they would have to eat more than 3 cups at a meal, or 5 ½ cups of chickpeas (0.42g of leucine per half cup).
For older adults who want to eat a more plant-based diet, ensuring adequate highly bioavailable protein that are also rich sources of leucine is essential to retain muscle – so I recommend “prioritizing protein” along with eating plenty of non-starchy vegetables, like broccoli, green beans, and leafy greens.
Prioritize Protein to Retain Muscle
“Prioritizing protein” means to first decide what protein you are going to eat at a meal, and then build the rest of the meal around that. For older adults, the protein should have between 25-30g of highly bioavailable protein, and 2.3-3g of leucine.
For breakfast, choosing high leucine proteins such as a cup of cottage cheese, or a cup of plain Greek yogurt will provide the needed minimum amount of highly bioavailable protein, as well as sufficient leucine. On the other hand, 2 eggs only contain 12 g of highly bioavailable protein, and 1.2g leucine less than half the recommended amount for older adults.
Choosing 4 oz (113g) of canned tuna for lunch will provide 4g of leucine and 21g of protein, and 3 oz of chicken breast (113g) will provide 2.4g of leucine and 26.5g of protein. To top up the leucine contents, you can serve that with some salad greens sprinkled with an ounce (28g) of pumpkin seeds that contains 0.7g of leucine or an ounce (28g) of sunflower seeds that contains 0.46g of leucine.
In terms of dinner options, while steak is one of the richest sources of leucine – having 3.4 g leucine per 4 oz (113g), cost is a factor. More cost-effective options for those that eat it are 4 oz. (113g) of pork chops which contains 27g of protein, and 2.5 g of leucine. Four ounces of ground beef contains only 16 g of protein but has 2.5 g of leucine, so boosting the protein content of the meal can be as simple as adding some Greek yogurt for dessert.
UPDATE (August 20, 2023) – Be sure to read the new article “Is Plant Protein and Animal Protein Equivalent” based on a recently published study.
Final Thoughts…
The quality of life of older adults and their health depends on remaining active, which requires adequate muscle mass, and preventing sarcopenia requires sufficient protein with all the essential amino acids, as well as enough of the amino acid leucine.
Given that we lose muscle mass at the rate of 1% per year after the age of thirty, which proteins we choose to eat at each of our meals is essential.
If you would like support ensuring you or a loved one eats sufficient high quality protein and leucine as well as other nutrients of concern, please reach out to me through the Contact Me form, above.
To your good health,
Joy
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References
- Keller K, Engelhardt M. Strength and muscle mass loss with aging process. Age and strength loss. Muscles, Ligaments and Tendons Journal. 2013;3(4):346-350.
- Lexell J. Human aging, muscle mass, and fiber type composition. Journals of Gerontology Series A: Biological and Medical Sciences. 1995;50:11–16
- Cruz-Jentoft AJ, Bahat G, Bauer J, Boirie Y, Bruyère O, Cederholm T, et al. Sarcopenia: revised European consensus on definition and diagnosis. Age Ageing. (2019) 48:16–31. 10.1093/ageing/afy169
- Hunter GR, Singh H, Carter SJ, Bryan DR, Fisher G. Sarcopenia and Its Implications for Metabolic Health. J Obes. 2019 Mar 6;2019:8031705. doi: 10.1155/2019/8031705. PMID: 30956817; PMCID: PMC6431367.
- Tessier AJ, Chevalier S. An update on protein, leucine, omega-3 fatty acids, and vitamin d in the prevention and treatment of sarcopenia and functional decline. Nutrients. (2018) 10:1099. 10.3390/nu10081099
- Berrazaga I, Micard V, Gueugneau M, Walrand S. The Role of the Anabolic Properties of Plant- versus Animal-Based Protein Sources in Supporting Muscle Mass Maintenance: A Critical Review. Nutrients. 2019 Aug 7;11(8):1825. doi: 10.3390/nu11081825. PMID: 31394788; PMCID: PMC6723444.
- Norton, L.E., Wilson, G.J., Layman, D.K. et al. Leucine content of dietary proteins is a determinant of postprandial skeletal muscle protein synthesis in adult rats. Nutr Metab (Lond) 9, 67 (2012). https://doi.org/10.1186/1743-7075-9-67
- El-Sohaimy, Sobhy & Mehany, Taha. (2015). Physicochemical and functional properties of quinoa protein isolate. Annals of Agricultural Sciences. 60. 10.1016/j.aoas.2015.10.007.
- Amino Acid Analysis of Soybean, https://www.drugfuture.com/chemdata/Soybean.html
- Bauer JI, Biolo G, Cederholm T, Cesari M, 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 Aug;14(8):542-59
- Nutrition Heart Beat, Leucine: perform better and maximize your muscle through diet, https://nutritionheartbeat.com/sports-nutrition/leucine-diet-muscle
- Rondanelli M, Nichetti M, Peroni G, Faliva MA, Naso M, Gasparri C, Perna S, Oberto L, Di Paolo E, Riva A, Petrangolini G, Guerreschi G, Tartara A. Where to Find Leucine in Food and How to Feed Elderly With Sarcopenia in Order to Counteract Loss of Muscle Mass: Practical Advice. Front Nutr. 2021 Jan 26;7:622391. doi: 10.3389/fnut.2020.622391. PMID: 33585538; PMCID: PMC7874106.
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