Not all topics in medicine receive the degree of attention they should. I want to shed some light on one such topic here – sarcopenia. I hope to clarify why this is an important topic and how to equip the reader with the most potent tools to prevent or slow this process.
Sarcopenia is the loss of muscle tissue and function. Much like our bones, muscles are dynamic, in constant flux throughout the day between breaking down and building up. Unfortunately, as we age our bodies become less sensitive to the signals that trigger muscle production, leaving muscle breakdown to take over, this unfavourable adaptation is known as anabolic resistance. As a result, with age, it becomes more difficult to maintain lean muscle mass and function and easier to accumulate fat mass. This is important as decreased muscle mass and function are major drivers of increased falls, fragility, disability and reduced physical capacity. By far the most serious health risk is falling. Falls contribute to the fourth leading cause of death in Canada (accidents), are the leading cause of injury in Canadians over 65 years and result in longer hospital stays than any other condition. Preventing falls saves lives!
How do we prevent muscle wasting?
Fortunately, the two most powerful tools for preventing muscle breakdown and promoting muscle growth are in our hands – nutrition and exercise. Dietary protein consumption and resistance exercise are key to long healthy muscles.
The recommended dietary allowance (RDA) for protein is 0.8g/kg/day (Ex: 150lb person = 68kg x 0.8g/kg = 54.4g/day protein). However, there are concerns this number is too low because the purpose of the RDA is to balance the offset of bodily proteins throughout the day, not to provide the optimum amount to promote new protein production. Furthermore, the studies used to estimate the RDA were done primarily in younger people and as highlighted above, the protein demands increase as we age due to anabolic resistance.
The goal of protein consumption is to ingest enough to stimulate muscle protein production and put the breaks on muscle protein breakdown. We know the required protein threshold is primarily impacted by age and activity level with younger populations being able to get away with less and older populations requiring more, independent of activity level. Studies looking at a large range of protein consumption and its effect on muscle protein production show a trend of higher protein amounts providing more muscle protein production. There is no formally established consensus, but the authors of a sarcopenia prevention review paper published in December 2021 recommend a protein target of 1.6-1.8g/kg/d, double the RDA (Ex: 150lbs person = 68kg x 1.6g/kg = 108.8g/day protein)
We also know we want to distribute our protein consumption throughout the day. Protein consumption within each meal has an ideal range – too little and we do not stimulate protein production, too much and we saturate our tissues, and the excess protein is not absorbed, known as the “muscle full effect”. The same authors recommend a minimum of 0.6g/kg/meal (Ex: 150lbs = 68kg x 0.6g/kg = 40g/meal). That is a great ideal target, however, obtaining 30-50 grams of protein in each meal of the day can be difficult. Prioritization should be given to your first and last meals of the day. This is because the overnight “fasted” state stimulates muscle breakdown and timing protein consumption in the morning and evening best blunts the duration of this period. As intermittent fasting has become more common, it is important to note that high-protein low-calorie foods provide muscle preservation benefits while maintaining a caloric deficit and the benefits of intermitting fasting. A simple quality protein powder in the morning achieves this.
Although protein consumption can reduce muscle protein breakdown, it is important to highlight resistance training should be the primary intervention for increasing muscle mass and function. Protein intake and resistance training work synergistically to support muscle retention as we age. When it comes to dosing resistance training, accumulating evidence suggests that previous recommendations for high-load, maximum repetition training is not the ideal strategy, especially as we age. Rather, less weight at higher repetitions more frequently improves muscle strength and function in older and younger adults. A minimum of at least 2 training sessions per week is recommended.
The steady loss of muscle mass and function as we age contributes significantly to falls, pain and overall decreased quality of life. Incorporating more protein throughout the day alongside a simple yet consistent resistance training program can enrich the quality of our lives now and have us on the path toward a long healthy fruitful life.
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Dr. Luke Mountjoy, ND