Growing up, I lived and died by the muscle-building rules outlined in magazines like Muscle & Fitness and Iron Man. Today, I’m still obsessed with muscle, but for different reasons. Muscle loss (i.e., sarcopenia) and its damaging consequences affect more than half of adults over fifty.[1] As unlikely as it seems, sarcopenia is serious business! It increases your risk for degenerative diseases and is a leading reason why adults are forced to leave their homes (i.e., become institutionalized). While Strength Training is the only way to prevent sarcopenia, what you eat also influences muscle maintenance. Knowledge of muscle-building nutrition has expanded significantly in recent years. Research indicates that total protein intake and timing influence muscle growth and health in older adults. Older adults often exhibit a skewed eating pattern regarding protein that doesn’t support muscle maintenance and development.
Here’s what we currently know about a muscle-building diet. Basing your protein requirements on the Recommended Dietary Allowance (RDA) will likely underestimate how much protein you need to build and maintain muscle. The Food and Nutrition Board of the Institute of Medicine (the organization establishing the RDA) has historically relied on research that uses an indirect measurement of protein turnover (i.e., nitrogen balance studies). This method is less accurate than modern methods that measure amino acid oxidation directly (i.e., the indicator amino acid oxidation method). The World Health Organization and the Institute of Medicine have recently recommended the IAAO as an acceptable method to assess protein requirements.[2]
Factors influencing protein requirements include body weight, activity level, age, and calorie intake. Naturally, the more you weigh, the more protein you require. Age is also a factor when it comes to protein. Many adults mistakenly think they need less the older they get. Aging decreases protein sensitivity (a condition known as anabolic resistance), which means you need more protein per pound of body weight the older you get.[3] Lastly, calorie intake also influences how much protein is required to build muscle. A hypocaloric diet (i.e., a diet that provides fewer calories than your body needs) increases your protein requirements. This is one reason why intermittent fasting can make it difficult to meet protein requirements and maintain muscle mass.
Every meal is an opportunity to activate the muscle-building process. Scientists call this muscle protein synthesis. A rapid increase in the number of essential amino acids (protein building blocks) in the blood appears to push the body into muscle protein synthesis.[4] This process is activated when you consume adequate amounts of protein. You can fill the gap by consuming complementary proteins if you’re a vegan or vegetarian and do not consume animal-based protein (i.e., meat, fish, eggs, cheese, etc.).
Complimentary proteins contain higher amounts of the amino acids that other foods are low in. For example, legumes (a plant-based protein source) contain the essential amino acid lysine, which is low in some grains. On the other hand, whole grains provide the essential amino acid methionine, which is lacking in lentils and some beans. Consuming complementary proteins at each meal makes sense if most of your protein is plant-based. Years ago, combining complementary proteins at every meal was considered unnecessary. However, new research methods that use direct protein turnover measures reveal that muscle protein synthesis is activated when significant quantities of essential amino acids are present simultaneously (i.e., at the same meal). Therefore, combining complementary proteins in adequate amounts at each meal (i.e., black beans and, brown rice, etc.) can provide the necessary amino acids to maximize muscle protein synthesis.
There’s no clear evidence that consuming most or all your protein from plants changes your protein requirements. However, you may need to consume more calories given that most plant-based proteins are less concentrated than animal proteins (i.e., one ounce of white fish contains 7 grams of protein for 25 calories, while ½ cup of black beans contains 7 grams for 115 calories). A protein’s quality depends on digestibility and amino acid profiles. Animal-based proteins (eggs, cheese, fish, etc.) score higher in both categories. Consuming more plant protein is the most straightforward way to offset this difference. Most studies recommend three to four protein meals/snacks daily to promote optimal muscle growth. You're a candidate for a protein supplement (i.e., shake, bar, etc.) if you don’t consume enough protein-rich whole foods [5]. For example, I blend a shake with protein powder, water, frozen fruits and vegetables, and ice to supplement my protein intake.
The American College of Sports Medicine, the Academy of Nutrition and Dietetics, and the International Society of Sports Nutrition recommend between 1.2 to 2.0 grams of protein per kilogram of body weight (an average of 1.6 grams per kilogram) for adults participating in Strength Training.[6] This translates to at least .7 grams of protein per pound of body weight per day. My weight of 185 lbs. equates to 130 grams of protein daily. This recommendation can be split into three or four meals or snacks (35 to 45 grams of protein each). If you weigh more than your target weight, use an estimated ideal body weight to calculate your protein needs. See the MEDFITNESS Protein Guide in the studio for a list of how much protein various foods contain.
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Richard J. Wolff, RDN
References
1. Janssen I, Heymsfield SB, Ross R. Low relative skeletal muscle mass (Sarcopenia) in older persons is associated with functional impairment and physical disability. J Am Geriatr Soc. (2002)
2. J Nutr 153: 12, 3472, 3489, 2023.
3. Protein and Exercise. Sports Nutrition: A Handbook for Professionals., Sixth Edition, 2017. Academy of Nutrition and Dietetics.
4 . Environmental Nutrition., Volume 42., Issue 9., September 2019.
5. British Journal of Sports Medicine. Volume 52, Issue 6. 2018. https://bjsm.bmj.com/content/52/6/376
6. Thomas DT, Erdman KA, Burke LM. American College of Sports Medicine Joint Position Statement. Nutrition and Athletic Performance. Med Sci Sports Exerc. (2016).
7. Protein Intake and Muscle Function in Older Adults. Curr Opin Clin Nutr Metab Care. 2015 May; 18(3): 248–253. doi: 10.1097/MCO.0000000000000162