Dietary protein: guidelines, requirements and a lack of common sense Douglas Paddon-Jones, Ph.D. The University of Texas Medical Branch
Overview 1. protein metabolism 2. building muscle in response to a protein-rich meal 3. translating science into practice 4. priority areas: aging - physical inactivity hospitalization 5. negative consequences of extra protein? 6. sarcopenia and a new strategy
Maintaining Muscle Mass and Function Synthesis Balance Breakdown Muscle growth Malnutrition Inactivity Illness/Injury Hormones Exercise Nutrition Muscle loss
Protein Synthesis (%/h) Stimulating Muscle Growth with Protein 0.14 0.12 * * 0.1 0.08 0.06 0.04 0.02 50% increase Young Elderly 0 Fasting 30 g protein Symons et. al. AJCN, 2007
Protein Synthesis (%/h) Protein Synthesis and Portion Control - a message of moderation - 30 g protein 90 g protein 0.14 0.12 * * * * 0.1 0.08 0.06 0.04 0.02 0 Fasting 30 g protein Fasting 90 g protein Young Old ~1.2 g/kg/day for 180 lb individual Symons et. al. AJCN, 2007 Symons et. al. JADA. 2009
Net Muscle Protein Synthesis (mg Phe/leg) Age-related protein dose-response 60 6 g 50 Young 40 30 20 10 Elderly 5 g 8 g 0 More than ~25 g protein Less than ~15 g protein 6 g Katsanos et. al. AJCN, 2005
Protein Synthesis (%/h) Synergistic Effect of Protein and Exercise 0.18 0.16 * * 0.14 0.12 100% increase * * 0.1 0.08 0.06 0.04 0.02 50% increase Young Elderly 0 Fasting Protein meal Protein + Exercise Symons et. al. JNHA, 2010
Timing of Protein and Exercise Meal Appearance in plasma Peak anabolic window Whey Protein Amino Acids 10-20 minutes Consume 0-60 minutes post exercise Intact Proteins (beef, fish etc.) 120+ minutes Consume approx.. 90 minutes before exercise * note, the timing relates only to muscle protein anabolism and does not take into account practical issues such as exercise performance, satiety, gastric comfort, hunger or coingestion of other nutrients.
Leucine Content of Foods 1 scoop (36 g) of whey protein isolate 3.2 g 1 scoop (36 g) soy protein isolate 2.4 g 4 oz. sirloin steak 2.0 g 4 oz. chicken breast 2.0 g 1 cup low-fat yogurt 1.1 g 1 cup fat-free milk 0.8 g 1 egg 0.5 g 2 tbsp. peanut butter 0.5 g 1 slice wheat bread 0.1 g Sources: USDA National Nutrient Database for Standard Reference, Release 20. and GNC WPI 28
Protein synthesis: % / hr Optimizing meal anabolism with Leucine 0.12 0.11 P=0.02 0.10 0.09 0.08 0.07 0.06 0.05 P=0.04 Post-absorptive Post-prandial 0 Day 1 (pre) Day 14 ( 2 weeks LEU)
Daily protein distribution - typical? - maximum rate of protein synthesis Catabolism Anabolism 10 g 15 g 65 g Total Protein 90 g A skewed daily protein distribution fails to maximize potential for muscle growth
Daily protein distribution - Optimal - maximum rate of protein synthesis Catabolism Anabolism 30 g 30g 30 g Total Protein 90 g ~ 1.3 g/kg/day Repeated maximal stimulation of protein synthesis increase / maintenance of muscle mass
Bed rest is a defacto treatment modality - if you re hospitalized you become inactive - % of Time 100 90 80 70 60 50 40 30 20 10 0 Inactive (0 steps/min) Low Activity (< 15 steps/min)
Inactivity and Aging Muscle Loss of lean leg mass (g) 250 0-250 -500-750 -1000-1500 -2000 Healthy Young 28 Days Inactivity 2% total lean leg mass Healthy Elders 10 Days Inactivity 10% total lean leg mass 3 times more muscle loss 1/3 the time All volunteers consumed the RDA for protein Paddon-Jones et. al. 2004 Kortebein et al. 2007
Protein Synthesis (%/h) Inactivity reduces muscle protein synthesis 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Day 1 Day 10 * 30% 24 h muscle protein synthesis during 10 day of inactivity in elders (stable isotope methodology) Kortebein et al. 2007
Protein Synthesis (%/h) Protein combats inactivity-induced muscle loss 0.1 0.09 0.08 Day 1 Day 10 - older adults - # 0.07 0.06 * 30% 0.05 0.04 0.03 0.02 0.01 0 Normal Diet Normal Diet + Amino Acids Normal Diet Normal Diet + Amino Acids Ferrando & Paddon-Jones et. al. 2009
grams Are our older inpatients eating enough? 100 80 60 40 20 0 Presented Consumed Protein Carbohydrate Fat per meal Paddon-Jones, pilot data
Loss of lean leg mass (g) Muscle Loss in Hospitalized Elders 250 0 Healthy Young 28 Days Inactivity Healthy Elders 10 Days Inactivity Elderly Inpatients 3 days hospitalization -250-500 -750-1000 -1500-2000 2% total lean leg mass 10% total lean leg mass 10+ % total lean leg mass Paddon-Jones, Pilot Data
The Protein Myth Adults eat more protein than they need True: most adults eat more protein than the minimum to prevent deficiencies But: minimum needs optimum health
Dietary protein and Bone the myth Increased protein causes calciuria and will ultimately weaken bone
Dietary protein and Bone the reality Protein Ca 2+ [Ca 2+ ] + Moderate protein diets (1-1.5 g/kg/day) are associated with normal calcium metabolism Ca 2+ Low protein intakes ( 0.8 g/kg/day): intestinal calcium absorption is reduced and levels of parathyroid hormone increase, causing the release of calcium from bone Feskanich D, et al. Am J Epidemiol 1996;143:472-9. Cooper C, et al. Calcif Tissue Int 1996;58:320-25
Protein and Renal Function Institute of Medicine: protein content of diet is not related to progressive decline in kidney function with age."
(kg) (kg) Sarcopenia: - traditional model - 55 Lean Body Mass 35 Fat Mass 50 45 40 35 30 20 30 40 50 60 70 80 30 25 20 15 10 5 20 30 40 50 60 70 80 Age (years) Age (years) Holloszy, Mayo Clin Proc. 2000
Lean muscle mass (kg) Alternate model of muscle loss - developing tactical nutrition interventions - 31 29 27 25 23 21 19 17 15 40 44 48 52 56 60 64 68 72 76 80 84 88 Age (yrs)
Prevention and treatment strategies - muscle mass & function - PREVENTION: a). Consume a moderate amount of high-quality protein, 3-times per day b). Consume protein in close proximity to physical activity TREATMENT: a). React aggressively with nutritional support to reduce the rapid loss of muscle and strength associated with physical inactivity
Summary Hypertrophy is slow, but atrophy can be exceedingly fast Benefits of exercise and high quality protein are not age dependent The RDA for protein is not sufficient in many circumstances 25-30 g of protein maximally stimulates muscle protein synthesis Distribution of protein throughout the day is key Moderation and common sense are still the key theme
Madonna Mamerow, Ph.D. Fellow Kirk English Doctoral Student Joni Mettler, Ph.D. Fellow Christopher Danesi Coordinator