2.6.2. Creatinine and Protein Supplements Flashcards
Recommended intake of protein
0.8 g/kg body (ideal body) weight/day
What are high quality proteins?
Where do we get them?
contain many essential amino acids (9)
His, Iso, Leu, Lys, Met, Phe, Thr, Trp, Val
usually from: dry beans and meat, chicken, or fish products
What are low quality proteins?
Where do we get them?
lacks some essential amino acids required for human diet
from: many vegetables
What happens in cases of high-protein diets, when very low in calories/protein of low quality or biologic value get a NEGATIVE NITROGEN BALANCE?
Body protein is degraded as AAs are converted to glucose. Even with high quality protein, ammonia and urea levels rise, putting stress on the kidneys.
What is the major end product of nitrogen metabolism? Follow the track of ammonia out of the body
Urea.
ammonia created by oxidative deamination reactions (involving amino acids), which can only be excreted as urea
this conversion is the urea cycle (ornithine cycle), which occurs in the liver
urea is excreted at the kidneys
Where did dietary standards come from?
Food and Nutrition Board (FNB) in 1940 came up with standards for war fighters
Dietary Reference Intakes (DRI)
a system of nutrition recommendations from the institute of medicine
Recommended Dietary Allowance (RDA)
daily dietary intake level considered sufficient by the FNB to meet the requirements of nearly 97-98%. This does NOT take into account the physically active
RDA for men and women is what for protein?
.8 g of protein per kg body weight (.36g/lb)
RDA changes based on activity.
What is the protein RDA for people who have:
- Low to moderate activity
- Endurance training
- strength and weight training
- High energy with insufficient calories
low to moderate activity = 0.8-1.0 g/kg
endurance training = 1.2-1.4 g/kg
strength and weight training = 1.2-1.7 g/kg
high energy w/ insufficient calories = 1.5-2.0 g/kg
Effective limits on protein in a meal
anything above .25 +/- .05 g/kg/meal of protein will not given any significant benefit
this typically lands around 20-25 g per serving
Estimated Average Requirement (EAR)
amount of nutrition needed to meet about 50% of population’s needs
Acceptable Macronutrient Distribution Range (AMDR)
reflects an intake range with a reduced risk of chronic disease
What percent energy of your total intake is protein?
protein = 10-35% total energy intake
Tolerable Upper Intake Levels (UL)
highest level of daily consumption that data so far have shown no side effects in humans without medical supervision when used indefinitely
insufficient data to define an upper limit for protein intake at this point in time
PDCAAS
Every protein source has a score associated with it called the Protein digestibility-corrected amino acid score (PDCAAS)
The amount of protein that is oxidized is increased by consuming protein in amounts higher than the RDA, and protein turnover increases with increased protein consumption as well
What does this mean about the excess protein consumed?
This means that the excess consumed protein is NOT being used for building muscle, but instead for energy (when using protein for energy, it is not an energy efficient process)
How much of muscle is protein? Water?
Muscle is only 20% protein
Most of it (75%) is water!
Concerns with high protein diets:
- generates an excess acid load
- fish and meat are highest
- plants are lower (leafy greens super low) - increase loss of calcium in the urine
- decreased intake of carbohydrates in exchange for proteins
- higher fluids needed with higher protein diets
2 primary stimulants to muscle protein synthesis
- Muscle contraction increases muscle protein synthesis
- Food intake
meal = increase in muscle protein synthesis
Compare Fast vs. slow protein
Fast
- increase blood AA rapidly
- might be better in the case of aging and preventing muscle wasting
- example: Whey (in milk!)
Slow
- slower increase in blood AA, but blood AA lasts longer
- help inhibit muscle breakdown by keeping blood AA level higher longer, so no need to break down muscles
- example: Casein (in milk!)
Muscle Mass Accretion
Muscle building
What is gain of lean muscle based on?
Gain in lean muscle mass based ONLY on the dietary source of protein
Whey vs. Casein on muscle building
Whey protein promotes a much greater insulin response than Casein
This does help prevent muscle wasting, HOWEVER, this does not dictate where the protein will be going or how it will be used
What are Essential amino acids?
cannot be synthesized by the body, so must be consumed in the diet
What are Conditionally Essential AAs?
the body CAN produce them, but this production can become the rate-limiting step in a series of reactions, so these AAs can become conditionally essential
the above means that they may not be synthesized in adequate amounts during highly demanding conditions
Leucine appears to be a specific signal for protein synthesis. What does it become in the body and what does this molecule do?
becomes Beta-hydroxy-beta-methylbutyrate (HMB)
common supplement and potential signaling molecule for protein synthesis
what 3 amino acids are needed to make creatine?
arginine
glycine
methionine
What does creatine phosphate do for us?
Creatine phosphate transports high-energy phosphate from the mitochondria to actinomyosin fibers and provides ATP for muscle contraction
Creatinine is produced non-enzymatically from creatinine phosphate, and a constant amount (dependent on body mass) is released into the blood each day and excreted by the kidneys
How should you use creatine in a muscle building diet?
3 g/day loads muscles maximally
may cycle on and off for periods of 28 days
NOT a booster of muscle performance (causes weight increase)
What muscle fibers may store more muscle creatine?
type II muscle fibers may store more muscle creatine
Muscle damage results in the release of creatine kinase (CK) into the blood; CK catalyzes reversible reaction:
creatine + ATP ←> creatine phosphate;
What molecule in the blood reveals that you have had a heart attack?
release of heart isozyme confirms heart attack has occurred
What is GFR and how is it related to Creatine Kinase?
creatinine kinase is cleared by the kidneys; used to approximate glomerular filtration rate (GFR); normally 100 mL/min; can use inulin because freely filtered (neither resorbed nor secreted)
Formula for GFR?
GFR = U(insulin) * V/P(insulin) = C(insulin)
