Transcript HSC 4572: Selected portions Chapter 6

Valerie Schulz, MMSc, RD, LD/N, CDE
 Compare
essential to non-essential amino
acids
 State the outcome if essential amino acids
are missing
 Discuss various roles of protein in humans
 Describe fate of amino acids/protein
consumed with sufficient carbohydrate vs a
carb-poor diet
 Identify major forms of protein malnutrition
 Discuss why consuming too much protein is
not recommended
 Summarize advantages/risks of vegan diet
 Amino
acids (aa): links in the chains of proteins
 General structure of amino acids:
(side
group) - varies
H–H-N –
(amino
C–
H
C–O-O-H
(acid group)
group)
 The
nitrogen (N) makes protein different from
carbohydrates or fats
 The side group makes each aa different, and
more complex than carbs or fats
(review of what was learned in HUN 2002)
 Unlike
CHO and fat, protein contains
___________
 Each building block of protein, the ________
__________, bind with ___________ bonds.
 Human bodies (can / cannot) make essential
amino acids.
 What makes one amino acid different from
another? The ______ group
 How many amino acids are there? ______
(Pg 191; heading is ‘How do Amino Acids Build Proteins?’)
 Primary
sequence is determined by the _____
blueprint.
 Secondary structure caused by attractions of
___________ groups.
 Tertiary structure caused by folding of the
protein as electrically charged side groups are
attracted to __________ and orient to the
outside of protein. The side groups that have a
neutral charge are repelled by water and
attracted to each other; they tuck themselves
_________ the protein structure.
 (Review
of Chapter 3 – you tell me)
 Mouth: (does any protein digestion happen here?)
 Stomach:


(2 things happen here)
Denatured/unfolded by ________
e_______________ break proteins into smaller chunks
 Small
intestine: many e_________, secreted into
the small intestine by the pancreas or made in
the small intestine, break up the chunks
(don’t need to know specific names)
 Absorbed as ________ __________, into the blood
 Large
intestine: (does any protein absorption happen here?)
 Each
human protein has a distinctive
sequence, leading to a specific 3-D shape and
function.
 The variety of possible sequences for amino
acid strands is tremendous (compare 26
letters of alphabet, and how many words are
in unabridged dictionary)
A
single human cell may contain as many as
10,000 different proteins, each one present
in thousands of copies.
 The
following slide shows the hemoglobin
molecule, exemplifying:


3-D structure of proteins
Function is related to shape:




notice how the protein chains, shown in color, bend so
that the heme molecule is held in place.
Iron atom is held by heme.
Function of hemoglobin is to carry iron, & oxygen
Peer into the blue, green, purple and orange
chains to see the primary sequence of the amino
acids that determines the final shape of the
protein, so it is perfect to carry heme
 Protein
carriers transport amino acids into
the intestinal cells.


The aa might be used in the intestinal cell for its
own purposes (intestinal cells are remade ~every
3 days)
If not needed in the intestinal cell, aa move on
into the blood on the way to the liver.
 Important
point: EVERY protein we eat is
broken down to amino acids before it is
remade into human proteins. So we cannot
eat an enzyme to help our digestion, because
it would be denatured in the stomach.
(Pg 194; the Variety of Proteins, Nutrients and Gene Expression)
 Every
cell nucleus contains the DNA for making
__________ human protein, but cells do not
make them all.

Some genes are “expressed” and others are not
depending on the cell type.

For example, only cells of the pancreas express the gene for
the protein hormone insulin.
 Nutrients
do not change DNA structure, but they
greatly influence genetic expression
(will not be tested on protein synthesis, Figure 6.6, pg 195)
 Those
who suffered through HUN 2002 with
me will remember the following cartoon slide
 It likens the long strand of DNA to a
“sentence”, and then considers the smaller
gene piece as a “word” in that sentence
 The blue part is the actual codes that stand
for each amino acid
 The green parts are the all important control
areas, where what we eat will have an
impact on how often (or not) this protein is
expressed. (Like omega-3 fats causing more
anti-inflammatory proteins to be made.)
Genes can be thought of as 'words' along the DNA 'sentences'.
 Amino
acids with similar structures use the same
transport systems to enter intestinal cells
 As a result, amino acids may compete with one
another for absorption, ie, excess of one may
slow absorption of the other that uses the
same system
 When single amino acid supplements are
consumed, the supplemented aa may
overwhelm the transport system
 This reduces the absorption of the other amino
acids using the same system.
 Joe
takes an excess of amino acid “A”, which
uses the same transport or carrier proteins as
amino acids “B” and “C”
 All the carrier proteins get filled up with
“A”, because there is so much of it
 There is not enough space on the carrier
proteins to transport “B” or “C”, so less of
those two are absorbed
 Especially if “B” or “C” are essential amino
acids, Joe will be creating a deficiency by
taking an excess of “A”
Building materials: for
growth/maintenance [muscle, collagen]
Hormones: messengers; some are proteins
Regulators of fluid balance: proteins hold
1.
2.
3.
water in the cells or in the plasma (blood). In
protein malnutrition, blood levels fall too low,
water ‘leaks out’ in between the cells, causing
edema
Enzymes:
4.
1.
2.
3.
4.
Digestion (break down)
Build (ex: bones)
Transform (ex: amino acid into glucose)
Enzyme action: figure 6-7 (changed from 6.9)
1.
Acid-Base regulators: proteins have negatively
charged surfaces, can attract loose H+ ions
“buffers”
2.
Transporters: 1. hemoglobin carries oxygen
from lungs to all cells; 2. lipoproteins carry lipids
in the watery blood; 3. special transport proteins
carry vitamins & minerals
3.
Antibodies: designed to destroy specific antigen
(ex: virus)
4.
Source of energy (glucose): gluconeogenesis –
making glucose from protein
 When
insufficient carbohydrate and fat are
consumed to meet the body’s energy need,
food protein and body protein are sacrificed
to supply energy.
 The
____________ part is removed from each
amino acid, and the resulting fragment is
oxidized for energy.
 No
storage form of amino acids exists in the
body.
 When



an amino acid arrives in a cell, it can be:
Used as is to build protein
Altered somewhat to make another needed
compound, such as the vitamin niacin
Dismantled to use its amine group to build a
nonessential amino acid

The remaining carbon, hydrogen and oxygen atoms can be
converted to glucose or fat
 In
a cell starved for energy with no glucose or
fatty acids:


The cell strips the amino acid of its amine group
(nitrogen part) and uses the remainder of its
structure for energy
The amine group is excreted from the cell and then
from the body in the urine
 In
a cell that has a surplus of energy and amino
acids, the cell



takes the amino acid apart
excretes the amine group
converts the rest to glucose or fat for storage
 Amino
acids are “wasted”
(won’t be used as protein) when:




Energy is lacking from other sources (either not
enough kcal and/or not enough carb).
Protein is overabundant (can’t store it)
An amino acid is oversupplied in supplement form.
The quality of the diet’s protein is too low (too few
essential amino acids).
© 2012 John Wiley & Sons, Inc. All rights reserved.
 To
be used efficiently as protein, protein must
be accompanied by:



ample carbohydrate and fat (kcal)
(“Protein-sparing” effect of carbohydrate)
vitamins and minerals.
 Protein
quality is influenced by a protein’s
digestibility and its amino acid composition.



Amino acids from animal proteins are most easily digested
and absorbed (over 90%)
Amino acids from legumes are next (80 to 90%)
Amino acids from plant foods vary (70 to 90%)
 High-quality
proteins – provide enough of all of
the essential amino acids needed to make new
proteins
 Low-quality proteins – do not provide all the
essential amino acids


If a nonessential amino acid is unavailable from
food, the cell synthesizes it
If the diet fails to provide an essential amino acid,
the cells begin to conserve the amino acid and
reduce their use of amino acids for fuel.
 If
a person does not consume all essential
amino acids needed, the body’s pools of
essential amino acids will dwindle:


First, blood and muscle proteins are dismantled
to provide the needed essential amino acids
Finally, body organs are compromised.
 If
food “A” lacks essential amino acids (if it is a
low-quality protein), then the amino acids in
food “A” can be used only if essential amino
acids are present from another source.
 If
food “A” is paired w/another low-quality
protein food that fills in the gap, then the two
together provide all essential amino acids, giving
the same benefit as a high quality protein.
 See following slide (you will not be tested on the
names of the amino acids that are complementary, just
know the concept)
 The
DRI recommendation for protein intake
depends on size and stage of growth
recommended intake is 0.8 gram per
kilogram of body weight per day
 DRI
 Minimum



is 10 percent of total calories
2000 kcal x 10% = 200 kcal
200 kcal / 4 kcal per g protein = 50 g protein
50 g protein spread over 3 meals is ~15-20g/meal
 Athletes
may need slightly more (1g per kg)
I
just wanted you to be exposed to the
concept on the following slide
 It is used more in intensive care and research
situations than it would be in day-to-day
nutrition care or education
 Now
that we have covered all the basics of
protein, will consider the effects of lack of
protein or too much protein on disease.
 PEM
occurs in two main forms:
K___________________ (acute protein deficiency)
 M_____________ chronic food (protein & energy) deficiency

 PEM
is not unknown in the United States, where
millions live on the edge of hunger.







Inner cities
Rural areas
Some elderly people, especially those living alone
Hungry and homeless children
People suffering from anorexia nervosa
People with wasting illnesses such as AIDS, cancer, or drug and
alcohol addictions
GI issues that have slowed or stopped the intake of food:
esophageal strictures, intestinal blockages
Variable
Marasmus
Kwashiorkor
Onset
Earlier, usually in
first year
Later, after breastfeeding has stopped
Growth Failure
significant
Not much
Edema
No
yes
Blood protein
concentration
Not much change
Very low
Skin changes
Not usually
Red patches & boils
Fatty liver
no
yes
 Marasmus
- without adequate nutrition:

Muscles, including heart, weaken

Brain development in children stunted, learning impaired
Metabolism slows, body temperature is subnormal
Person is apathetic, does as little activity as possible
Growth ceases; child is no larger at 4 than was at 2
Digestive enzymes in short supply, intestinal cells cannot
replenish, absorption fails
Blood proteins, incl hemoglobin, not produced: anemia
Antibodies degraded to provide amino acids for other
synthesis, leaving the person an easy target for infection,
including ones that cause diarrhea







Infections w/PEM cause 2/3 of child death in developing world
 Kwashiorkor
Without severe wasting of body fat
 Proteins that maintained fluid balance diminished,
fluid leaks out of blood, accumulates in belly and
legs, resulting in edema
 Skin loses elasticity, cracks; sores develop, fail to
heal
 Fatty liver, caused by lack of protein carriers to
transport fat out of liver
 Fatty liver loses some function, including ability to
clear toxins, which accumulate, reducing appetite

 There
is no benefit from eating excess protein:
 Why?
 In
human beings, a high-protein diet increases
the kidneys’ workload but this alone does not
appear to damage healthy kidneys or cause
kidney disease. (What does?)
 In people with kidney problems, a high-protein
diet may speed the kidneys’ decline.
 People with Stage 1 – Stage 4 can slow
progression to Stage 5 (dialysis) by eating lower
protein.
 Diagnosed
by comparing BUN with creatinine
to estimate GFR: glomerular filtration rate
 According to the National Kidney Foundation,
normal results range from 90 - 120
mL/min/1.73 m2. (not necessary to memorize)
 GFR decreases with age
 Levels below 60 mL/min/1.73 m2 for 3 or
more months are a sign of chronic kidney
disease (CKD)
 GFR below 15 mL/min/1.73 m2 is a sign of
kidney failure; requires immediate medical
attention. Dialysis usually when GFR <7.







Eat a healthy diet: Include a variety of grains,
especially whole grains, fresh fruits and vegetables
Choose a diet that is low in saturated fat and
cholesterol and moderate in total fats
Limit intake of refined and processed foods high in
sugar and sodium
Choose and prepare foods with less salt or high
sodium ingredients
Aim for a healthy weight, consume adequate calories
and include physical activity each day
Consume the DRI for vitamins and minerals
Keep protein intake within the Daily Reference Intake
(DRI) level recommended for healthy people (0.8g/k)
(potassium ,phosphorus usually not restricted unless blood levels above
normal)










Including grains, fruits and vegetables, but limiting whole
grains and certain fruits and vegetables if blood tests show
phosphorus or potassium levels are above normal.
A diet that is low in saturated fat and cholesterol
Limiting intake of processed foods high in sodium; prepare
foods with less salt or high sodium ingredients.
Aiming for a healthy weight by consuming adequate
calories, including physical activity
Limiting protein intake to the level determined by the
dietitian’s assessment of individual needs (as low as
30g/day)
Consuming DRI for water soluble vitamins; C limited
Vitamin D and iron may be tailored to individual
requirements.
Limiting phosphorus if blood levels of phosphorus or PTH
are above normal.
Limiting calcium if blood levels are above normal.
Limiting potassium if blood levels are above normal.
 Alcohol
abuse
 Drug-induced:
http://www.medicinenet.com/liver_disease/
page2.htm#what_are_the_causes_of_liver_di
sease
 (from above link): start reading at ‘What are
the causes of liver disease?’, read down
through alcohol abuse, cirrhosis. Under drug
induced, just notice the part about
acetaminophen. Start again at infectious
hepatitis, then stop at hemochromatosis.




Limited amount of protein. A damaged liver cannot
process protein very well. This causes a build-up of
ammonia in the bloodstream.
More carbohydrate. Carbohydrate is the body's energy
supply. A healthy liver makes glycogen from
carbohydrate. The glycogen is then broken down
when the body needs energy. A damaged liver can't
do this. Without glycogen, more carbohydrate is
needed from the diet to make sure the body has
enough energy.
A moderate amount of fat. Fat provides calories,
essential fatty acids, and fat-soluble vitamins.
A limited amount of fluids and sodium. Liver damage
can cause high blood pressure in the major vein of
the liver. This can result in ascites, a fluid build-up in
the abdominal cavity. Limiting fluids and sodium can
help prevent this. (you saw the ascites picture in
Chap 3 controversy on alcohol )
 Common
diet prescription for ESLD (End stage
liver disease):





30-60g protein (usually works out to 8-15% of
kcal); lower amounts if history of high blood
ammonia, or encephalopathy. High quality protein
is more desirable (why?)
60-70% kcal as carbohydrate; fruit is encouraged.
Usually have to demonstrate how to add extra.
Carbs do not need protein carriers for absorption.
25-30% kcal from fat (about same as is
recommended for population at large). Fat needs
protein carriers.
2gm (2000mg) Na+ or less. This is the difficult
part to implement
Fluid restriction: not always
 What


constitutes a vegetarian diet?
Many subsets of reducing/omitting animal foods
Describe varieties :




“flexitarian”
Lacto-ovo
Lacto
vegan
 People
who eat well-planned vegetarian
diets suffer less often from chronic
diseases than people whose diets center
on meat

Strong evidence links vegetarian diets with
reduced incidences of chronic diseases. Benefits
include:





Less obesity
Defense against certain cancers (colo-rectal
associated with red and processed meats. Fish eaters
had lowest levels of cancer in a UK study)
Less heart disease (blood lipids stepwise: vegan,
lacto-ovo, meat-eating)
Less high blood pressure (specific etiology unclear:
lower body weight and higher K+ probable)
May help prevent diabetes, osteoporosis, diverticular
disease, gallstones, and rheumatoid arthritis
 When
meat (animal muscle) is omitted,
USUALLY see these changes:




Lower saturated fat
Increased whole grains (is whole wheat bread a
whole grain? You have discussed this!)
Increased fruit, vegetable, legumes - all
associated with improved health
Positive changes associated with a vegetarian diet
are the same changes associated with a WHOLE
foods pattern of eating
A
balanced, adequate diet in which lean
meats and seafood, eggs, and milk play a
part in addition to fruits, vegetables and
whole grains can be very healthy.
 On

the other hand:
Meat lovers who shun all vegetables have no
adequate substitutions for these foods (unlike
vegetarians who can find suitable replacements
for meat).
Both vegetarian and meat-containing diets, if not
properly balanced, can lack nutrients.
 Poorly planned meat eater’s diets may lack:

vitamin A
 vitamin C
 Folate
 fiber


Poorly planned vegetarian diets typically lack:






Iron
Zinc
Calcium
omega-3 fatty acids
vitamin D
vitamin B12.
Area
Vegan
Meat consuming
Pregnancy
If start pregnancy too
thin, need extra kcal.
Choose well to get
enough B12 and iron.
Receive enough B12, iron, zinc.
If also consume dairy, usually
enough Ca++, Vit D
Childhood
Vegan foods higher
fiber, child may get full
before achieve all
nutrients.
Same
Adolescence Teens wisely choosing
lots of fruits & vegs can
meet national dietary
objectives, rare in US.
Iron still an issue.
Very easy to choose foods that
exclude fruits and vegetables,
initiate fatty streaks, etc.
Aging
Poor dentition leads to problems
chewing meat; texture change
not well liked.
Softer cooked vegetable
proteins aesthetically
pleasing
Nutrient
Vegan
Meat consuming
Protein
Legumes, seeds, nuts, soy
Animal muscle, egg, dairy
Iron
Dark green leafy, dried
fruits (hi kcal), legumes
(w/ Vit C)
Animal muscle, egg (w/ Vit
C)
Zinc
Legumes, nuts, seeds
Animal muscle, dairy
Calcium
Dark green leafy, nuts,
Dairy
seeds (fortified plant milk)
Omega-3
Marine algae, flaxseed,
walnuts
Fatty fish