Higher protein intake, around 1.2 to 1.6 grams per kilogram of body weight, is more optimal for muscle protein synthesis, especially for physically active individuals.
Resistance exercise plays a crucial role in preserving muscle mass, so incorporating strength training into one's routine is highly recommended, especially for older adults.
Advancements in food processing have improved the quality of plant-based proteins, making them comparable to animal-based sources in terms of essential amino acid content.
Regular exercise, particularly resistance training, helps maintain sensitivity to anabolic stimuli, combats anabolic resistance, and preserves muscle mass, especially in older individuals.
Deep dives
Importance of protein intake for muscle maintenance
Protein intake is crucial for maintaining muscle mass, especially as we age. The recommended daily intake for adults is around 0.8 grams per kilogram of body weight, but recent research suggests that higher protein intakes, around 1.2 to 1.6 grams per kilogram of body weight, may be more optimal, especially for physically active individuals. These higher protein intakes can promote muscle protein synthesis, which is essential for building and preserving muscle. However, the effect of protein intake is relatively small compared to the benefits of regular exercise, especially resistance training. It's also important to distribute protein intake evenly throughout the day rather than relying on one large meal. While animal-based protein sources are generally considered higher quality than plant-based sources, the quality of plant-based proteins has improved with advancements in processing methods. Thus, plant-based protein sources can still provide sufficient essential amino acids for muscle protein synthesis.
The impact of disuse and disease on muscle loss
Disuse and disease can significantly accelerate muscle loss, especially in older individuals. Even short periods of immobilization or reduced physical activity can lead to a catabolic crisis, where muscle loss occurs at a faster rate. For older adults, these events can be particularly detrimental, as the rate of muscle loss becomes more pronounced. Hospitalization or prolonged periods of bed rest are examples of disuse events that can trigger catabolic crises and result in severe muscle loss. To counteract this, older individuals should focus on maintaining an even distribution of protein intake throughout the day, with particular emphasis on consuming more protein in the morning. Additionally, resistance exercise plays a critical role in preserving muscle mass, so incorporating strength training into one's routine is highly recommended.
The importance of protein quality and the role of leucine
Protein quality, specifically the content of essential amino acids, plays a crucial role in promoting muscle protein synthesis. Among the essential amino acids, leucine is considered the most potent stimulator of muscle protein synthesis. Animal-derived protein sources are generally higher in essential amino acids compared to plant-based sources. However, advancements in food processing have led to improvements in the quality of plant-based proteins. Cooking methods and the isolation of plant proteins have made plant-based protein sources more comparable to animal-based sources in terms of essential amino acid content. While supplementation with leucine alone can stimulate muscle protein synthesis, it is generally recommended to focus on obtaining sufficient protein from a variety of food sources rather than relying solely on individual amino acid supplements.
Anabolic resistance and the role of physical activity
Anabolic resistance refers to a reduced sensitivity of muscles to anabolic stimuli, such as exercise and protein intake. As we age, there is a natural decline in physical activity, which contributes to anabolic resistance. Inactivity and insulin resistance are both factors associated with anabolic resistance. Physical activity, especially resistance training, can help maintain sensitivity to anabolic stimuli and mitigate the effects of anabolic resistance. Additionally, maintaining overall insulin sensitivity through regular exercise and a healthy diet can further support muscle protein synthesis. It is important for older individuals to stay physically active and engage in regular exercise to combat anabolic resistance and preserve muscle mass.
The benefits of physical activity
Maintaining physical activity levels through aerobic and resistance exercises is crucial for overall health. Being as active as possible is essential, and aerobic exercises help improve cardiovascular fitness while resistance exercises contribute to strength and muscle growth. Recommendations suggest doing resistance exercises two times a week, but higher frequency and duration can lead to additional benefits. The goal is to go from a sedentary lifestyle to being physically active, as even small changes can have significant positive effects on physical and mental health.
Exercise guidelines and the importance of recovery
The ideal frequency for resistance training is two times a week, with each session lasting 30 to 45 minutes. While there are variations in exercise routines, basic exercises like push-ups, squats, and various weightlifting techniques can be done with body weight or minimal equipment. Recovery plays a vital role in exercise effectiveness, as it allows the body to repair and rebuild muscle tissue. The mechanical stress from exercise stimulates muscle protein breakdown, and recovery ensures protein synthesis occurs to repair and strengthen the muscles. Adequate rehydration, refueling, and protein intake contribute to proper recovery.
Understanding the role of hormones in muscle protein synthesis
Hormones like testosterone and growth hormone play important roles in muscle protein synthesis. Testosterone is not as influential as once believed, as studies have shown that both men and women experience similar muscle growth with resistance training. Growth hormone stimulates collagen synthesis and strengthens tendons and muscles, making it essential for overall muscle health. While some supplements claim to boost hormone levels, the body's natural hormone production and regulation are more effective and safer. Hormone replacement therapy can be beneficial for individuals with clinically low hormone levels under proper medical supervision.
The potential benefits of omega-3 and creatine supplements
Omega-3 fatty acid supplements have shown potential for reducing muscle atrophy and promoting muscle growth, especially in older individuals. They have anti-inflammatory properties and can resolve inflammation, contributing to optimal muscle function. Creatine supplementation has been extensively studied and proven to be safe and effective for muscle growth and cognitive performance. It primarily benefits high-intensity exercise and may aid older individuals in maintaining muscle mass. Gradual supplementation and selecting monohydrate form are recommended for optimal results.
Stuart Phillips, PhD, is a professor of kinesiology at McMaster University in Hamilton, Ontario, Canada, where he also serves as the director of the Physical Activity Centre of Excellence. His research centers on the roles exercise and nutrition play in influencing human skeletal muscle protein turnover and how these lifestyle factors influence body composition, especially as we age.
In this episode, we discuss:
(00:00) Introduction to Dr. Stuart Phillips
(07:16) Why muscle is important for longevity
(14:34) Is the importance of muscle mass (per se) overstated?
(16:48) Is the RDA on protein too low?
(19:03) Minimum vs. optimal protein intake (for athletes)
(19:29) Why older adults need more protein
(24:52) Caloric restriction vs. higher protein for aging
(28:04) What is a catabolic crisis?
(29:40) Effects of space flight on muscle
(36:16) Practical tips for protein intake
(39:34) Protein timing and the anabolic window
(41:27) Most important factors for hypertrophy
(43:57) Should we supplement leucine?
(45:46) Does plant protein support hypertrophy?
(56:30) Causes of anabolic resistance
(58:22) What types of exercise and how much?
(01:06:56) Protein and rest as tools for recovery
(01:08:14) Mechanisms of muscle protein synthesis and breakdown
(01:08:31) Does rapamycin inhibit hypertrophy?
(01:13:07) What is Dr. Phillips doing to age well?
(01:15:25) Hormonal responses to exercise
(01:17:09) Sex differences in hypertrophy
(01:19:38) Effect of menopause on muscle
(01:20:03) Do testosterone boosters work?
(01:21:56) Does growth hormone improve muscle?
(01:26:30) Androgen replacement therapy (benefits vs. drawbacks)
