#299 ‒ Optimizing muscle protein synthesis: the crucial impact of protein quality and quantity, and the key role of resistance training | Luc van Loon, Ph.D.
Professor Luc van Loon, an expert in skeletal muscle metabolism, discusses the critical role of protein in muscle protein synthesis, differentiating between protein types and forms. He also explores the intricate connections among physical activity, lean muscle mass, and dietary protein for performance and recovery.
Deep Dive Analysis
16 Topic Outline
Luc van Loon's Background and Research Focus
Fuel Selection and Metabolism During Endurance Exercise
Intramuscular Lipids in Athletes vs. Diabetics
Post-Exercise Glycogen and Fat Replenishment Windows
Transition to Protein Metabolism: Amino Acids as Building Blocks and Signals
Measuring Muscle Protein Synthesis Using Stable Isotopes
Protein Digestion, Absorption, and Fate of Excess Amino Acids
Impact of Food Processing and Texture on Protein Digestion
Whey vs. Casein: Digestion Rate and Anabolic Response
Optimal Protein Quantity and Distribution for Muscle Synthesis
Muscle Loss with Aging and Inactivity: The Catabolic Crisis Model
Anabolic Resistance: Causes and Mitigation Strategies
Protein and Exercise for Hospitalized Patients
Efficacy of Collagen Protein Supplements
Plant-Based Protein Quality and Quantity Considerations
Unanswered Questions: Brain Protein Metabolism
7 Key Concepts
Stable Isotope Tracers
These are non-radioactive isotopes (e.g., Carbon-13) used to label metabolites like carbohydrates and amino acids, allowing researchers to track their movement, oxidation, digestion, absorption, and incorporation into tissues like muscle protein in vivo.
Intramyocellular Lipids (IMCL)
These are fat droplets stored inside muscle fibers. In endurance athletes, IMCLs are a dynamic and readily used energy source, while in sedentary or diabetic individuals, high IMCLs often indicate low turnover and contribute to insulin resistance.
Athlete's Paradox
This refers to the observation that both endurance-trained athletes and individuals with type 2 diabetes can have high levels of intramyocellular lipids. The crucial distinction is that athletes actively utilize and replenish these stores, whereas in diabetics, they remain largely static with low turnover.
Muscle Protein Synthesis (MPS)
The biological process by which muscle cells create new proteins, essential for muscle growth, repair, and adaptation. It is directly stimulated by the availability of amino acids (particularly leucine) and physical exercise, with different types of exercise promoting synthesis of specific protein types (e.g., myofibrillar vs. mitochondrial).
Catabolic Crisis Model
A hypothesis proposing that age-related muscle loss (sarcopenia) is not a continuous, gradual decline but rather a cumulative effect of discrete, short periods of reduced physical activity (e.g., illness, injury) from which older individuals do not fully recover their muscle mass.
Anabolic Resistance
A diminished responsiveness of muscle protein synthesis to anabolic stimuli such as protein intake and exercise. This phenomenon is commonly observed in older individuals and during periods of physical inactivity, making it harder to maintain or gain muscle mass.
Splanchnic Sequestration
A term describing the uptake and retention of ingested amino acids by the gut and liver after a meal, before they reach the systemic circulation to be available for other tissues like muscle. This process can limit amino acid delivery to muscle, potentially contributing to anabolic resistance.
12 Questions Answered
The body prioritizes the oxidation of ingested glucose, saving endogenous liver and muscle glycogen stores. Combining glucose with fructose can slightly increase the maximum absorption rate, potentially up to 1.3-1.4 grams per minute for high-end athletes.
While both groups may have high levels of intramyocellular lipids (fat within muscle cells), athletes actively use and replenish these stores, making them a dynamic fuel source, whereas in diabetics, these stores have low turnover and contribute to insulin resistance.
Muscle glycogen can be largely replenished within 24 hours, especially if carbohydrate intake is optimized. Intramuscular fat stores take longer, up to 48 hours, to fully replete.
Researchers infuse stable isotope-labeled amino acids (e.g., Carbon-13 phenylalanine) into the bloodstream. Muscle biopsies are then taken over time to measure the incorporation of these labeled amino acids into new muscle proteins, yielding a fractional synthetic rate.
Foods that are more processed or have a finer texture (e.g., ground beef vs. steak, cooked eggs vs. raw eggs) tend to be digested and absorbed more rapidly, leading to a quicker and potentially greater spike in amino acid availability for muscle protein synthesis.
Both are highly digestible, but whey protein is digested and absorbed much more rapidly than micellar casein, leading to a faster and higher spike in blood amino acids and a greater initial stimulation of muscle protein synthesis. Casein's slower digestion leads to a more sustained, but lower, amino acid release.
For healthy, active individuals, approximately 20 grams of high-quality protein concentrate is often considered optimal to maximize muscle protein synthesis for 4-5 hours. However, larger amounts (e.g., 100 grams) can sustain elevated synthesis rates for longer periods (up to 12 hours).
While consuming protein immediately after exercise can lead to a greater acute muscle protein synthesis response, consistent training means every meal (before and after) will benefit from the increased muscle sensitivity. Over 24-48 hours, the total protein intake and training consistency are more critical than immediate post-workout timing.
Yes, even in a caloric deficit, engaging in resistance training (e.g., twice a week) can prevent muscle mass loss, making the muscle more responsive to protein intake and preserving lean body mass.
Anabolic resistance, a reduced muscle response to protein and exercise, is complex and can involve issues with digestion, absorption, splanchnic sequestration, muscle perfusion, and intracellular signaling. Physical activity is a potent countermeasure, as even short periods of inactivity induce it, and exercise can restore muscle sensitivity to protein even in older individuals.
While collagen is rich in glycine and proline, studies have not shown a significant increase in muscle connective tissue protein synthesis rates with collagen supplementation beyond the effect of exercise itself, at least in the short term. It is also a 'poor' protein for overall muscle protein synthesis due to its imbalanced amino acid profile compared to complete proteins.
Many plant-derived proteins are lower in essential amino acids like lysine or methionine. To ensure a balanced amino acid profile, it's important to consume a variety of plant-based protein sources that can complement each other. For vulnerable populations (e.g., sick, elderly, those with low food intake), animal-derived proteins may be more efficient due to higher quality and digestibility.
16 Actionable Insights
1. Maintain Muscle with Protein & Exercise
To maintain muscle mass, continuously stimulate it with anabolic stimuli like food intake (especially protein) and exercise, as muscle breakdown is constant.
2. Daily Protein Intake Target
Aim for 1.6 grams of protein per kilogram of body mass per day for muscle maintenance, and closer to 2 grams per kilogram per day for muscle gain, especially with high training volume.
3. Optimal Protein Per Meal
Healthy, active individuals should aim for approximately 20 grams of protein per main meal to maximize muscle protein synthesis for up to 4-5 hours. Adjust this to 30-40 grams or more for whole foods to compensate for slower digestibility.
4. Exercise Enhances Anabolic Response
Engage in consistent training, especially resistance training, as it makes muscles more sensitive to the anabolic properties of amino acids, enhancing the impact of every meal on muscle protein synthesis.
5. Combat Anabolic Resistance with Activity
Physical activity can normalize age-related anabolic resistance, making older muscles as responsive to protein as younger muscles. Even one week of inactivity can induce significant anabolic resistance.
6. Resistance Training on ADT
Men undergoing androgen deprivation therapy (ADT) should engage in resistance training (2-3 times per week) to increase muscle mass and strength, and attenuate fat mass gain, effectively counteracting the negative side effects of ADT.
7. Prevent Muscle Loss in Caloric Deficit
Even when in a caloric deficit, engage in resistance training (at least twice a week) to prevent muscle mass loss, which is crucial for overall health.
8. Pre-Sleep Protein for Muscle Synthesis
Consume a protein-rich snack before sleep, as it is rapidly digested and absorbed, stimulating muscle protein synthesis overnight. This can aid recovery from training and attenuate muscle loss in older or hospitalized individuals.
9. Exercise for Glucose Homeostasis
Regular exercise improves glucose homeostasis by promoting insulin-independent glucose uptake into muscle cells, an effect that can last up to 24-48 hours.
10. Chew Food Thoroughly
Chew food thoroughly to accelerate digestion and absorption, which can expedite muscle protein synthesis, especially for whole foods.
11. Cook Eggs for Better Digestion
Cook eggs instead of consuming them raw to achieve more rapid digestion and absorption of protein, leading to a better anabolic response.
12. Prioritize Protein Quality for Vulnerable
For individuals with reduced food intake (e.g., due to illness, cancer, pain), prioritize high-quality, animal-derived protein sources due to their superior digestibility and amino acid profile.
13. Compensate Plant Protein with Quantity/Variety
If consuming plant-based proteins, ensure a well-balanced meal with different plant sources to compensate for potential deficiencies in specific amino acids, or consume larger quantities to overcome lower quality.
14. Maximize Glucose During Endurance
During endurance exercise, continuously supply glucose from the gut (60-70g/hr, or up to 1.3-1.4g/min with fructose for high-end athletes) to save liver glycogen and prevent its too-fast depletion.
15. Replenish Intramuscular Fat for Multi-Day Events
For multi-day endurance events, ensure adequate fat intake to replete intramuscular lipid stores, as it takes one to two days to replenish them for subsequent performance.
16. Collagen Supplementation (Limited Evidence)
While collagen is rich in glycine and proline, current data does not strongly support a unique benefit for muscle connective tissue protein synthesis from collagen supplementation over other proteins, at least over short periods. Its potential benefit for tendons, ligaments, bone, and cartilage is still being investigated.
7 Key Quotes
You have a building site where you actually have bricks being delivered. And the bricks themselves pick up the phone and call the brick layers to come over.
Luc van Loon
Look at their own arm and realize that in 50 to 100 days, they have a new arm. It's completely refurbished. That is amazing.
Luc van Loon
If you're physically active, you are more of what you just ate.
Luc van Loon
If you become physically less active, you are less of what you just ate.
Luc van Loon
With one week of inactivity, I can make a young muscle respond completely like a senescent muscle.
Luc van Loon
At any age, and that's also a hundred plus, the muscle is still very responsive to physical activity.
Luc van Loon
It's ridiculous that people go on ADT and are not immediately getting resistance training in addition to it because it prevents all the negative side effects.
Luc van Loon
2 Protocols
Maintaining Muscle Mass During Caloric Deficit
Luc van Loon- Engage in resistance training at least twice a week.
- Ensure adequate protein intake.
Attenuating Muscle Loss in Hospitalized Patients
Luc van Loon- Provide protein-rich snacks between dinner and bedtime (e.g., cheese cubes).
- Encourage light physical activity between meals (e.g., walking stairs, standing up from toilet multiple times).