Dietary protein: guidelines, requirements and a lack of common sense

Transcription

1 Dietary protein: guidelines, requirements and a lack of common sense Douglas Paddon-Jones, Ph.D. The University of Texas Medical Branch

2 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

3 Maintaining Muscle Mass and Function Synthesis Balance Breakdown Muscle growth Malnutrition Inactivity Illness/Injury Hormones Exercise Nutrition Muscle loss

4 Protein Synthesis (%/h) Stimulating Muscle Growth with Protein * * % increase Young Elderly 0 Fasting 30 g protein Symons et. al. AJCN, 2007

5 Protein Synthesis (%/h) Protein Synthesis and Portion Control - a message of moderation - 30 g protein 90 g protein * * * * 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

6 Net Muscle Protein Synthesis (mg Phe/leg) Age-related protein dose-response 60 6 g 50 Young Elderly 5 g 8 g 0 More than ~25 g protein Less than ~15 g protein 6 g Katsanos et. al. AJCN, 2005

7 Protein Synthesis (%/h) Synergistic Effect of Protein and Exercise * * % increase * * % increase Young Elderly 0 Fasting Protein meal Protein + Exercise Symons et. al. JNHA, 2010

8 Timing of Protein and Exercise Meal Appearance in plasma Peak anabolic window Whey Protein Amino Acids 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.

9 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

10 Protein synthesis: % / hr Optimizing meal anabolism with Leucine P= P=0.04 Post-absorptive Post-prandial 0 Day 1 (pre) Day 14 ( 2 weeks LEU)

11 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

12 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

13 Bed rest is a defacto treatment modality - if you re hospitalized you become inactive - % of Time Inactive (0 steps/min) Low Activity (< 15 steps/min)

14 Inactivity and Aging Muscle Loss of lean leg mass (g) 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 Kortebein et al. 2007

15 Protein Synthesis (%/h) Inactivity reduces muscle protein synthesis Day 1 Day 10 * 30% 24 h muscle protein synthesis during 10 day of inactivity in elders (stable isotope methodology) Kortebein et al. 2007

16 Protein Synthesis (%/h) Protein combats inactivity-induced muscle loss Day 1 Day 10 - older adults - # * 30% Normal Diet Normal Diet + Amino Acids Normal Diet Normal Diet + Amino Acids Ferrando & Paddon-Jones et. al. 2009

17 grams Are our older inpatients eating enough? Presented Consumed Protein Carbohydrate Fat per meal Paddon-Jones, pilot data

18 Loss of lean leg mass (g) Muscle Loss in Hospitalized Elders Healthy Young 28 Days Inactivity Healthy Elders 10 Days Inactivity Elderly Inpatients 3 days hospitalization % total lean leg mass 10% total lean leg mass 10+ % total lean leg mass Paddon-Jones, Pilot Data

19 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

20 Dietary protein and Bone the myth Increased protein causes calciuria and will ultimately weaken bone

21 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: Cooper C, et al. Calcif Tissue Int 1996;58:320-25

22 Protein and Renal Function Institute of Medicine: protein content of diet is not related to progressive decline in kidney function with age."

23 (kg) (kg) Sarcopenia: - traditional model - 55 Lean Body Mass 35 Fat Mass Age (years) Age (years) Holloszy, Mayo Clin Proc. 2000

24 Lean muscle mass (kg) Alternate model of muscle loss - developing tactical nutrition interventions Age (yrs)

25 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

26 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 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

27 Madonna Mamerow, Ph.D. Fellow Kirk English Doctoral Student Joni Mettler, Ph.D. Fellow Christopher Danesi Coordinator