Protein

Question 1

Information on protein metabolism?

Answer 1

• Proteins provide structure to all cells in the human body
• Many proteins are enzymes that increase the rate of metabolic reactions
• Amino acids have central roles in the metabolism of many organs and tissues
• Amino acids are precursors for the synthesis of body proteins
• Amino acids are regulators for the synthesis of neurotransmitters, hormones, DNA, and RNA

Question 2

What is the ratio between nitrogen and protein?

Answer 2

1g nitrogen = 6.25g protein

Question 3

What are the three steps of calculating nitrogen balance?

Answer 3

1) Determine nitrogen excretion (e.g., urine, faeces, sweat) (in grams per 24hr period)
2) Determine nitrogen intake (Protein intake as grams per day divided by 6.25
3. N balance = 2 minus 1

Question 4

What are the limitations of Nitrogen balance? (Tissues, sensitivity, positive balance)

Answer 4

• No information on tissues
• Lack of sensitivity
• Positive balance may not relate to lean body mass

Question 5

What is the formula for net protein balance?

Answer 5

Muscle protein synthesis - Muscle protein breakdown

Question 6

Do higher protein diets cause a decline in kidney and liver function?

Answer 6

• No data that links higher protein diets to renal disease
  The FAO/WHO report concluded “the protein content of diet is not related to progressive decline in kidney function with age”

Question 7

Do higher protein diets cause bone loss?

Answer 7

• (Shams-white et al. Am J Clin Nutr. 2017): “Current evidence shows no adverse effects of higher protein intakes. Although there were positive trends on BMD at most bone sites
• (Mangano et al. Curr Opinion Clin Nutr Megan Care. 2014) says “protein’s positive effect on bone health is augmented by increased calcium intake”

Question 8

What is the synthesis rate of muscle protein pools? (Percentage turnover, g of protein, renewal period)

Answer 8

• Muscle protein turns over between 1-2% per day
• In a healthy man this equates to approximately 300-600g of muscle protein
• Complete renewal of body protein over 3-4 months

Question 9

How does different modes of exercise affect distinct muscle protein synthesis? (Resistance, endurance)

Answer 9

• Resistance exercise increases the synthesis of force producing proteins
• Endurance exercise increases the synthesis of energy producing proteins

Question 10

Why is it important for athletes to optimize protein requirements beyond the RDA? (3 points)

Answer 10

1. Repair replace and remodel damaged proteins (e.g. muscle)
2. Support lean tissue maintenance
3. Support optimal function of the immune system

Question 11

What are the results of synergistic anabolic actions of exercise plus protein? (MPS, post exercise, augmented fed state)

Answer 11

1. Demanding exercise stimulates a prolonged elevation of muscle protein synthesis (MPS)
2. In the post-exercise period, the MPS response to protein ingestion is enhanced
3. This augmented fed-state MPS response may persist for 1-2 days post-exercise

Question 12

What is the optimal protein dose for Muscle protein synthesis in young adults?

Answer 12

Ingestion of 30g protein is sufficient to maximise MPS rates during recovery from a single bout of endurance exercise

Question 13

How much protein per day is needed to maximise whole-body anabolism in resistance-trained men?

Answer 13

2.0g/kg/day, 2.5 x higher than the current RDA

Question 14

Does milk consumption promote greater muscle protein synthesis than soy protein?

Answer 14

Yes, applies to both short term and long term

Question 15

What is in Milk that makes it more effective than soy milk?

Answer 15

20% whey protein, 80% Casein

Question 16

How important is dietary protein quality for muscles?

Answer 16

Animal proteins contains more essential amino acids, particularly the branched chain amino acid, leucine

Question 17

What are the differences in digestibility of amino acids and total tract digestibility of crude protein in relation to animal-based proteins versus Plant-based proteins? (Protein score, total tract digestibility)

Answer 17

• Animal proteins easily have the highest protein score compared to plant-based proteins.
• In particular animal proteins from the total tract digestibility of crude protein.

Question 18

Is there a role for ‘slow’ proteins in muscle remodelling: Eat before you sleep?

Answer 18

Yes, evidence to show increase in muscle fibre size

Question 19

Can a plant-based diet really save the planet and support optimal human health?

Answer 19

• They focus on the idea that lower meat consumption will significantly lower Greenhouse Gases
• And that animal foods may harm human health, comes largely from epidemiology

Question 20

How good are plant proteins for muscle anabolism?

Answer 20

Ingesting a large dose of mycoprotein (Quorn) resulted in a similar postprandial muscle anabolic response to whey protein.

Question 21

What type of weight is lost during energy deficit? (Contribution of fat-free mass)

Answer 21

In persons with normal weight, the contribution of fat-free mass loss often exceeds 35% of total weight loss

Question 22

How do we overcome the blunting of muscle protein synthesis during energy restriction?

Answer 22

• Resistance exercise increased MPS equal to energy balance
• 15g and 30g after REX in energy deficit increased MPS approx 16, 34 and 42% above resting energy balance

Question 23

Can higher dietary protein promote high quality weight loss during energy deficit?

Answer 23

Yes, more and quicker weight loss, whilst maintaining and even gaining lean mass

Question 24

What are some factors that may help lean mass preservation/gain during energy restriction?

Answer 24

• Exercise training (particularly resistance)
• High dairy protein
• Higher protein diet
• Early-post exercise protein intake
• Balanced distribution of daily protein intake