biochem exam 2 - nutrition Flashcards
what are the 9 essential amino acids?
and because they are essential, how does it relate to our diet
histidine (arginine for babies)
isoleucine
leucine
lysine
methionine
phenylalanine
threonine
tryptophan
valine
HILL MPTTV
protein turnover-
nitrogen balance-
positive status
negative status:
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)
Protein in foods
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
Mutual Supplementation with Complementary Proteins: an illustrative example
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
Protein Quality
“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
PDCAAS
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….
PDCAAS (continued)
Determine digestibility – Pinto beans: 79%
- PDCAAS = Digestibility x AA Limiting Score * Pinto beans: PDCAAS = 0.79 x 0.84 = 0.66
Health Effects: Inadequate Protein Intake
Develops when diet includes too little protein or lacks essential amino acids.
- Many adverse consequences
- Often referred to as protein-energy malnutrition (PEM)
Health Effects: Excessive Protein Intake
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
XS Protein Intake Effects (cont.)
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.
Recommended Protein Intake
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.
Celiac Disease
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).
Gluten-free diets
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.
Gluten-free foods
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
Protein Supplements
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 ($)
AA Supplements
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.
Vegetarian Diets
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)
Vegetarian Diet - must include:
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
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
- 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: 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
- 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
What is the recommended daily protein intake for a person who weighs 100 kg and consumes 3000 kcal/day?
- 50-175g
- 75-260g
- 300-1050 g
- 375-500g
- 1650-1950g
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
