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“Food Protein: Need and Quality”
How much do we really need, and what kind should we eat?
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DRI Recommendations (Dietary Reference Intakes)
“DRI recommended intake is 0.8 gram for each kg (2.2 lbs) of body weight.” “Or a minimum of 10% of total calories.” @ end of class, we’ll calculate your need.
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What about athletes? Athletes may need slightly more, but the increased need is well covered by most Americans’ diets. So most of us are already eating more than we need.
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Special Needs The DRI committee set some special requirements for some groups. “Children: no more than 35% of total calories” This is substantially higher than the rest of the population!
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The DRI committee also suggests that vegetarians need more iron than the general population.
There are a few other factors that could affect your protein needs…
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The Body’s Health “Infection: body needs extra protein for immune system.” The body is manufacturing antibodies, which are made of protein. People who are malnourished also need more protein, although they may have trouble digesting it.
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“Nitrogen Balance” So why are the recommendations what they are?
In order to figure out how much protein we need, we have to look at the nitrogen we eat and compare it to the nitrogen we need to excrete.
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“In healthy adults, nitrogen-in (consumed) = nitrogen-out (excreted).”
How can we measure someone’s nitrogen excreted? Under controlled conditions, we can examine the nitrogen totals in urine, sweat, feces. Then we can calculate what the person needs to consume to make up for these losses.
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Balance of Nitrogen Value
“Normal adults: nitrogen equilibrium.” There are other situations, where one is greater than the other, We’ll take a look at who this would be.
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“Nitrogen-in>nitrogen-out: person is making more proteins than they are losing.”
Who might be in this situation? “growing child, person building muscle, pregnant woman”
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“Nitrogen-in<nitrogen-out: losing protein.”
Who might be in this situation? “sick person, astronaut” Why an astronaut?
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Where should I get my protein?
We can put proteins into two categories. “High-quality proteins provide enough of all essential amino acids;” “Low-quality don’t.”
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In making our proteins, we need all of them!
If we don’t have enough, our body responds to this. “If not enough aa’s are around, the body:” “1. Breaks down internal proteins” Why would this be bad?
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Or “2. Limits synthesis of proteins.”
Why would this be bad? Compare this to a printer trying to make stationary for Jana Johnson without any N’s.
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In this case, the N was missing.
In the body, “the aa we are short on is called the limiting amino acid.” Partially completed proteins are not held on to until the diet improves. Rather, the protein is dismantled so that the other aa’s are available.
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“Complimentary Proteins”
So if we need all of the amino acids, and no food contains them all, what would be a logical way to construct a diet? “A diet should contain different proteins, so that all aa’s are consumed.”
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“When we eat multiple aa-rich foods, our bodies build complementary proteins.”
This means that what we don’t get from one food, we get from another.
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“This plan is called mutual supplementation.”
In this example, legumes and grains go together because they supply different aa’s.
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Protein Digestibility
Can you think of any proteins that are hard to digest? Hooves, horns, hair, etc. We can’t use the protein! “Digestibility is an important characteristic of proteins.”
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If we wanted to make a piece of meat more tender, how would we cook it?
“Moist heat improves digestibility.” If we dry it like jerky, it gets tougher and less digestible.
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Benefit of Living Here In the U.S., we have access to all different proteins! In countries where food is limited, they may have adequate quantity, but they may only have one type of aa. That can cause malnutrition.
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