Protein quality/requirements

Question 1

what factors affect quality of protein sources

Answer 1

• major= AA composition/pattern
• digestibility (hydrolysis + availability of AA/chemical integrity)

Question 2

how to assess protein quality

(methods)

Answer 2

• indicator AA oxidation method (IAAO)
• bioassay
• AA scores
• protein digestibility-corrected AA scores (PDCAAS)

Question 3

what is AA balance

Answer 3

amount needed to replace losses
balance between the intake, utilization, and excretion of AA
imbalance can = deficiencies, reduced synthesis, excess waste

Question 4

what determines a person’s essential AA requirements

Answer 4

• age
• physiological state (pregnant/sick)
• quality of protein ingested
• lean mass (will increase demand)

Question 5

what is protein complementation

Answer 5

combining 2+ protein sources with different AA profiles in order to provide all essential AA in adequate amounts - essential AA missing from one is supplied by the other

Question 6

what are the DRIs for protein/AA intake

Answer 6

EAR = 0.66 g/kg/day
RDA = 0.8 k/kg/day
AMDR = 10-35%

Question 7

what are the pros/cons of the vegetarian diet

Answer 7

pro: help maintain healthy body weight, lower BP/CHD risk/T2D

con: over-reliance on one food/food group will not provide adequate nutrient range = can develop deficiencies

Question 8

what are the pros/cons of the carnivore diet

Answer 8

pro: excellent source of consistent high quality protein

con: positive association with increased BP/CHD risk/T2D/colon cancer

Question 9

at a low protein intakes, dietary protein is used less efficiently T or F

Answer 9

false, used more efficiently due to adaptation to low protein diet

Question 10

why are protein requirements higher when we are younger

Answer 10

• to support the more rapid tissue growth (muscle/organs) and bone formation
• higher rate of protein synthesis and degradation
• higher need for building/maintaining nutrient reserves

Question 11

why are protein requirements higher when pregnant/breast feeding

Answer 11

• building more tissues for fetal growth/development + more maternal tissue in uterus/breast/blood volume
• breast milk provides protein = need more intake to be able to produce it
• repair/maintenance of mother’s body

Question 12

what factor affects protein utilization

Answer 12

dietary non-protein energy
- insufficient energy intake = AA used for fuel instead of protein synthesis

Question 13

what happens when protein intake is inadequate

Answer 13

• decreased protein synthesis
• short term: impact of cells with rapid turnover
• long term: all organs/immune system affected

Question 14

how is protein nutritional status evaluated

Answer 14

• plasma protein levels (albumin, transferrin)
• assess rapid growing tissues (skin thinness, hair loss/growth)
• lean body mass

Question 15

what part of body is used in lean mass assessment? why?

Answer 15

mid-upper-arm muscle circumference/diameter because it is less affected by edema

Question 16

what is marasmus

Answer 16

energy + protein deficiency
- cause: diet lacking calories + protein + micronutrients + essential fatty acids
- symptoms: muscle wasting, subcut fat loss. growth retarded (<60% weight for age)
- onset: slowly, chronic PEU

Question 17

what is kwashiorkor

Answer 17

adequate energy, protein deficiency
- cause: decreased synthesis of enzymes/lipid transport, hypoalbuminemia
- symptoms: growth retarded (60-80% weight for age), edema, fatty liver, skin/hair change, anemia, diarrhea
- onset: rapid, acute PEU

Question 18

where/when does kwashiorkor occur

Answer 18

• developing countries: after breast feeding discontinues
• developed countries: major trauma (severe burns, sepsis), chronic malabsorption

Question 19

marasmus has a higher morality rate T or F

Answer 19

false, kwashiorkor has a higher morality rate

Question 20

what is the UL for protein

Answer 20

there is no UL for protein

Question 21

what are the outcomes of a high protein diet

Answer 21

• short term weight loss/calcium loss/ketoacidosis
• rabbit starvation of high lean meat intake (low fat and carb intake)
• adverse effects in patient with renal failure (lots of N waste for kidneys + electrolyte imbalance)

Question 22

the fraction of AA intake that is absorbed and accounts for ingested + fecal excretion of N is

Answer 22

apparent digestibility

Question 23

apparent digestibility that has been corrected for endogenous protein loss is called

Answer 23

true digestibility

Question 24

why are plant proteins a lower quality

Answer 24

• less complete AA range
• contain carbs
• protein may be encapsulated in cell wall/matrix = cannot access/digest the protein
• trypsin inhibitors (in legumes/cereal/raw egg whites)

Question 25

what can lower AA availability/digestibility in a food

Answer 25

• processing/storage at high ambient temps can lower bioavailability
• heat = irreversible Lys residue modifications
• strong acid treatments
• ultrastructural changes

Question 26

what is a limiting AA

Answer 26

the most deficient AA in a food item

Question 27

what is IAAO

Answer 27

indicator AA oxidation
- when 1 indispensable AA is deficient (limiting AA) the rest of the IDAAs above that level are oxidized

Question 28

what are the 4 major limiting AAs

Answer 28

Lys, Met, Thr, Trp

Question 29

how are AA scores determined

Answer 29

AA in test protein as a proportion of AA in reference protein

Question 30

how are PDCAAS determined

Answer 30

AA score corrected for digestibility (x fecal true digestibility)

Question 31

what animal source lacks an essential AA? what plant source has all essential AA?

Answer 31

animal: gelatin lacks Trp
plant: soy contains all