One of the most important things you can do to stay healthy and functional as you age is to preserve lean body mass. Unfortunately, we begin to lose lean tissue after the age of 30, and this process accelerates during late-middle age. By the time men and women reach their early 70s, 27% of women and 23% of men have difficulty walking a quarter mile or lifting 25 pounds. Most also have problems climbing a single flight of stairs.
Loss of muscle leads to other problems as well. Carrying more lean muscle is linked with better metabolic health and insulin sensitivity and loss of muscle tissue is correlated with insulin resistance. Muscle acts as a “sink” for glucose, sucking it in and helping maintain normal blood glucose levels.
Is it inevitable that you’ll lose muscle and become less functional as you age? Loss of functionality is due primarily to deconditioning and a gradual loss of muscle tissue, a problem known as sarcopenia. The combination of muscle atrophy from lack of physical activity and a diet low in protein and other essential nutrients accelerates the loss of muscle mass and strength related to aging.
Fortunately, there’s something you can do to preserve muscle mass and the ability to stay functional as you age – resistance train. Then make sure you’re eating a balanced diet with adequate amounts of protein. Of course, this raises a very important question – do you need MORE protein to build and maintain muscle as you age?
Are You Getting Enough Protein?
A small study published in the American Journal of Physiology, Endocrinology, and Metabolism looked at whether adults over the age of 50 need more dietary protein to fuel protein synthesis and whether the timing and distribution of protein intake matters.
Researchers divided 20 healthy women and men between the ages of 52 and 75 into 4 different groups. One group ate the recommended daily amount of protein (0.8 grams per kilogram), evenly divided across all 3 meals – breakfast, lunch, and dinner. These folks got roughly 33% of their daily protein at each meal. A second group ate the same amount of protein in an uneven distribution, getting most of their protein at dinner and less at breakfast and lunch. Two other groups ate almost double the amount of protein (1.5 grams per kilogram daily) with one group getting their protein in an uneven distribution and the other getting it evenly divided between their 3 daily meals.
Protein Quantity Matters For Protein Synthesis
The results of this study showed protein distribution across meals doesn’t seem to impact muscle protein synthesis. In other words, spacing protein evenly over the day and getting roughly similar amounts at each meal didn’t boost muscle protein synthesis in this study. What DID matter was protein quantity. Eating more TOTAL dietary protein (0.8 grams per kilogram daily versus 1.5 grams per kilogram daily) resulted in greater muscle protein synthesis in these older adults.
This study adds to a growing body of evidence that the standard recommendation of 0.8 grams per kilogram of body weight protein daily may not be enough to maintain lean body mass in people over the age of 50, especially when research suggests older adults experience some degree of “anabolic resistance,” the reduced ability to respond to anabolic stimuli that promote muscle growth. Studies show young adults experience increased muscle protein synthesis when they take in even small amounts of essential amino acids, around 10 grams, whereas older adults don’t. BUT older adults do respond with protein synthesis to higher quantities of essential amino acids.
One of the most important essential amino acids for muscle growth is leucine, one of the building blocks for muscle tissue – but leucine’s role extends beyond serving as a muscle building block. It activates a muscle-building pathway called mTOR (mammalian target of rapamycin), a pathway that turns on the “machinery” that synthesizes new muscle protein. mTOR is the signal that says, “Let’s make some protein!”
The muscles of older people seem to be less responsive to the mTOR signaling effects of leucine. You don’t lose the ability to synthesize new muscle tissue as you age, but you DO need more essential amino acids to turn on protein synthesis compared to when you were in your twenties. Plus, once you’re past the age of 50 you may not absorb as much of the protein you take in through diet. With fewer amino acids entering the bloodstream and reaching muscle tissue, muscle protein synthesis declines. The good news? A study in older men showed they were still able to synthesize adequate amounts of muscle proteins when they took in more protein and essential amino acids through diet.
What Does This Mean?
Once you’re past the age of 50, you may need more essential amino acids, including leucine, to boost muscle protein synthesis due to age-related anabolic resistance. According to some research, lack of physical activity itself is a contributing factor to anabolic resistance. Doing regular resistance training may help to prevent anabolic resistance and make your muscles more responsive to the protein you take in through diet.
Although it may not be necessary to space your protein intake evenly out over the day, as long as you’re taking in enough total protein, getting a dose of protein after a workout is still important. A number of studies show that consuming 20 to 30 grams of protein after a resistance training session boosts muscle protein synthesis, regardless of age. Some studies show this increased stimulus for protein synthesis persists for days after a resistance training session.
The Bottom Line?
After the age of 50, you may benefit from consuming up to twice the amount of dietary protein currently recommended for young adults to help overcome anabolic resistance. Regular resistance training and exercise, in general, is also a stimulus for making your muscles more responsive and capable of building muscle tissue. You don’t necessarily have to take a protein supplement to do this. Focus on getting your protein from a variety of sources – lean poultry, fatty fish, eggs and plant-based protein sources like tempeh, lentils, beans, and nuts.
With careful attention to your diet and a strong focus on resistance training, you can avoid the disabling effects of sarcopenia as you age.
References:
Endocrinology and Metabolism, 2014; 308 (1): E21 DOI: 10.1152/ajpendo.00382.2014
Aging, Physical Activity, and Health. Joy J. Shephard. (1997)
Am J Physiol Endocrinol Metab. 2005 May;288(5): E883-91. Epub 2004 Dec 21.
Am J Clin Nutr May 2005 vol. 81 no. 5 953-963.
Exerc Sport Sci Rev. 2013;41(3):169-173.
Related Articles By Cathe:
Anabolic Resistance: Why You Lose Muscle as You Age
5 Ways Your Workout Should Change after the Age of 50
Can Consuming Protein after a Workout Help You Build More Muscle?
New Study Suggests More Protein is Better for Building Muscle
Muscle Hypertrophy: What Limits the Ability of Your Muscles to Grow?
