biochem exam 2 - nutrition

Question 1

what are the 9 essential amino acids?

and because they are essential, how does it relate to our diet

Answer 1

histidine (arginine for babies)

isoleucine

leucine

lysine

methionine

phenylalanine

threonine

tryptophan

valine

HILL MPTTV

Question 2

protein turnover-

nitrogen balance-
positive status
negative status:

Answer 2

Protein Turnover: breakdown and synthesis of proteins, recycling amino acids

Nitrogen Balance:
– Positive status: The body synthesizes and consumes more protein than it degrades and excretes (OK for growing infants & children, pregnant women, and recovering patients)
– Negative status: The body synthesizes and consumes less protein than it degrades and excretes (except under severe stress, starvation)

Question 3

Protein in foods

Answer 3

Most people in the U.S. & Canada consume enough

• When food is scarce or “incomplete”, must consider
  – “Complete Protein:” contains all essential AA’s in needed amounts (esp. animal protein)
  – “Limiting AA:” essential AA; less than needed – Plant proteins are more diverse, and often
  incomplete (e.g., corn) (v. complete: soy, quinoa) * Vegetarian strategy: next slide

Question 4

Mutual Supplementation with Complementary Proteins: an illustrative example

Answer 4

legumes has
- Ile & Lys

Grains have
- Met & Trp

together you will get
- Ile, Lys, Met & Trp

so eating legumes and grains covers these amino acids

Question 5

Protein Quality

Answer 5

“High Quality:” digestible enough to provide adequate amounts of all the AA’s required for protein synthesis
– Animal protein: 90-99% HQ
– Plant protein: 70-90% HQ (due in part to digestion- resistant cell walls)

so animal protein is the best for getting high-quality protein

we can use the PDCAAS to measure protein quality
- it stands for protein digestibility corrected amino acid score

Question 6

PDCAAS

Answer 6

First, determine the Amino Acid Score, e.g. for Met:
- mg/g-protein AA reference pattern = 25
- mg/g-protein AA profile: pinto beans = 21.1

21.1/25 = 0.84 as the limiting score

limiting scores:
His: 1.67 x 0.79 = 1.31
Ile: 1.7 x 0.79 = 1.343
Leu: 1.4618 x 0.79 = 1.154
Lys: 1.352 x 0.79 = 1.06
Phe: 1.925 x 0.79 = 1.52
Thr: 1.6185 x 0.79 = 1.27
Trp: 1.257 x 0.79 = 0.99
Val: 1.565 x0.79 = 1.23

i dont think im doing this right but yeah….

Question 7

PDCAAS (continued)

Answer 7

Determine digestibility – Pinto beans: 79%

• PDCAAS = Digestibility x AA Limiting Score * Pinto beans: PDCAAS = 0.79 x 0.84 = 0.66

Question 8

Health Effects: Inadequate Protein Intake

Answer 8

Develops when diet includes too little protein or lacks essential amino acids.

• Many adverse consequences
• Often referred to as protein-energy malnutrition (PEM)

Question 9

Health Effects: Excessive Protein Intake

Answer 9

Many of the adverse effects are due to the fats (esp. saturated) associated with animal protein.

• Weight control: if high-fat
• Heart disease: increased risk associated with increased [homocysteine], which may result from ↑ coffee, smoking, ↓ B-vitamins

Question 10

XS Protein Intake Effects (cont.)

Answer 10

Cancer: correlation between increased intake of animal protein and cancer of the colon, breast, kidney, pancreas, prostate, ovaries

• Bone loss: without adequate Ca intake, high protein intake may accelerate bone loss (high intake → Ca excretion); but inadequate intake may compromise bone health
• Kidney disease: high-protein diet may require high nitrogen excretion, creating an added
  burden for the kidneys.

Question 11

Recommended Protein Intake

Answer 11

10-35% of daily energy intake (4 kcal/g; so, on a 2000-kcal diet, 50-175g)

Old Rec.: 10%

• Adult RDA: 0.8 g/kg/day (2.2 lb./kg)
• Higher for infants and children
• RDA same for athletes
• However, most of us (U.S. & Canada) already consume more than enough protein
• Problems begin around 2x the RDA.

Question 12

Celiac Disease

Answer 12

Immune disorder – to wheat gluten and
related proteins in barley and rye

Immune reaction damages intestinal tissue, resulting in GI disturbance and poor absorbance.

• Diet therapy: gluten-free diet (wheat, barley and rye, and foods derived from these).

Question 13

Gluten-free diets

Answer 13

Necessary for anyone with celiac disease
.
* Such diets have become popular, which has benefited suppliers of gluten-free foods, but there has been little research to document the health benefits of such diets for non-celiacs.

Question 14

Gluten-free foods

Answer 14

Gluten-containing wheat, rye, and barley add texture and flavor to foods.

• Replacements (most often rice) may not taste as good, may not contain as many nutrients (such as folate and iron), and may have more fat, sugar, or sodium (to improve taste).
• More rice may also mean more arsenic. (Moderation is the key.)

careful that gluten is replaced by other things and may have side effects

Question 15

Protein Supplements

Answer 15

Exercise, not supplements, builds muscle

• Carbohydrates used before proteins
• Very popular: whey protein powders
  – May increase protein synthesis, but not athletic performance
• Main beneficiary: the supplier ($)

Question 16

AA Supplements

Answer 16

With a few exceptions, single AA supplements are generally not beneficial
– Branched-chain AA supplements are popular as fuels, but not as good as glucose or FAs

• May help patients with liver disease, but not recommended for others
  – Lys suppress herpes infections? No evidence.
  – Trp may induce drowsiness, but adverse side effects have been observed.

Question 17

Vegetarian Diets

Answer 17

Advantages:
– Weight control
– Reduces risk for diabetes
– Blood pressure control (low body weight; low-fat, high-fiber diet)
– Decreased risk of heart disease
– Decreased risk of cancer (esp. colon cancer)

Question 18

Vegetarian Diet - must include:

Answer 18

Protein (milk & eggs [if in diet]; grains, legumes, seeds, nuts, vegetables; usually OK)

• Iron: because it may be poorly absorbed from plant foods (dark green leafy veg., legumes, whole-grain bread & cereal); but Vit. C helps absorption; usually OK
• Zinc: because it may be poorly absorbed from plant foods (whole grains, nuts, legumes)

Calcium: because absorption may be limited (fortified juices & soy milk, legumes, broccoli, sesame seeds, etc.)

• Vitamin B12: because it is found almost exclusively in animal-derived foods (also in fortified soy milk & cereals*, supplements)
• Vitamin D: but this is formed by exposure to the sun and is in many dairy products
• Omega-3 fatty acids: in some seeds, oils

P-IZC-B12D-03
protein, ions, vitamins in that order

Question 19

According to the data provided, what is the limiting amino acid?
1. His
2. Ile
3. Leu
4. Lys
5. Met (+Cys)
6. Thr
7. Trp

Answer 19

3. Leu
   I’ll just say that it is the limiting amino acid because it has the highest reference number (the data to the left) :) makes sense

Question 20

Question: If Digestibility = 84%, what is the PDCAAS of Leu product?
1. 0.42
2. 0.59
3. 0.65
4. 0.77
5. 0.84

Answer 20

3. 0.65
   (42.3/55) x 0.84 = 0.65 good :)
   the data from the right column is the numerator, the data to the left is the denominator, and multiply that value by the digestibility

Question 21

What is the recommended daily protein intake for a person who weighs 100 kg and consumes 3000 kcal/day?

1. 50-175g
2. 75-260g
3. 300-1050 g
4. 375-500g
5. 1650-1950g

Answer 21

Remember:
– 10-35% of daily energy intake
– 4 kcal/g
– (Adult RDA: 0.8 g/kg/day [2.2 lb./kg])
* Answer:
– (10-35%) x 3000 = 300-1050 kcal/day – (300-1050) / 4 g/kcal = 75-260 g