FN 225: Nutrition
Tamberly Powell, M.S., R.D.
Health Professions Division
Lane Community College
Eugene, Oregon

EXAM 3 next week (Week 7).  Online Review Quiz this week (Week 6)

 


FORUM for Week 6:

1. One of the Video Clips this week discusses some environmental problems of eating lots of beef. One thing mentioned to make more environmentally friendly food choices is to eat less meat, "Meatless Mondays".   What types of meat alternative dishes do you prepare?  How do you make them tasty?

2. Look at your Diet Analysis printouts.  Did you meet or exceed your protein recommendation?  How could you improve your protein intake? 


 

LECTURE 6A: Protein

First skim through the Lecture Outline:




Watch the following two Video Clips to help with filling out the following sections of your lecture outline.

I  Introduction
 II  The Structure of Amino Acids & Protein
 


Video Clip: Protein Structure
approximately 9 minutes

Here is the link to the above video:  https://www.youtube.com/watch?v=4BGLoSmFZLQ 


Here is a great animation, "What is a Protein," that shows the peptide bonding between amino acids.  You will not need to know the intricate details of this, but it is a nice overview of the structure of amino acids.

Once amino acids join together to form a polypeptide, then the protein strand coils and folds based on how the amino acids in the strand attract and repel one another.  Here is an illustration of that:

 

An important concept with proteins is that SHAPE determines FUNCTION.  When the wrong amino acids are bonded together when synthesizing proteins, the result is a different shaped protein, that does not function like it should.  An example of this is Sickle Cell Anemia (which is a genetic disorder).  Below is a picture of hemoglobin, which is globular in shape and when packed in red blood cells to deliver oxygen, it gives red blood cells a donut shape.

 

With Sickle Cell Anemia, DNA gives cells the incorrect message when bonding amino acids together to make hemoglobin.

 

 

The result is a crescent shaped red blood cell, that is sticky and does not transport oxygen like the non-sickle red blood cells.

This is the result of a different shaped protein!
 

III Functions of Proteins

As your text states, "proteins are amazing, versatile, and vital cellular working molecules.   Without them, life would not exist".

Proteins function as both structural and working proteins.  Structural proteins tend to be long and fibrous in nature, and working proteins tend to be globular in shape. 

Structurally proteins make up hair, skin, nails, bone, connective tissue, muscle and other vital organs.

Working proteins include:

  1. Hormones like insulin and glucagon 

  2. Enzymes like lactase, and maltase

  3. Transport proteins like lipoproteins (remember these help transport fat and cholesterol), cellular pumps, and hemoglobin (as discussed above hemoglobin transports oxygen).  If you are interested, here is an animation that shows "The Sodium-Potassium Pump."

  4. Plasma proteins help regulate fluid balance in the blood, and prevent edema.

  5. Antibodies to help fight infection.

  6. Protein can be used as an energy source, but carbohydrate and fat are preferred fuel sources.

The important way the muscles help provide energy for the brain is by having their amino acids rearranged to become glucose for the brain.  Our brain canNOT use fat for energy, at least not in any significant amount.

Below is a short video illustrating a few of the functions discussed above.

Here is a link to the above video: http://youtu.be/izwgt1C8Kus

How does our body get these structural and working proteins?  Our body makes them.  Amino acids which are the building blocks for these proteins come from the diet, recycled amino acids within the body, or our body synthesizes non-essential amino acids.



IV  Protein in the Diet- Quality

Measures of Protein Quality in a food include digestibility and how well the amino acid pattern of the protein supports growth.

A.    Digestibility.  Animal protein is more digestible than plant protein.  I'm not sure why this is, I have not been able to find a good answer.  Let me know if you know why.

B.    Amino Acid Pattern     
1.    Complete protein       
This is a protein in food that has all the ESSENTIAL amino acids (in the needed proportions) for building protein in the cells of the body.   Food sources for complete protein are listed in the document, "Food Sources and Health Benefits of the Macronutrients" which is posted in moodle.  Typically these are foods of animal origin, with the exception of soy.  One food not listed there is quinoa.  Quinoa along with soy are both examples of plant proteins that have all the essential amino acids (in the needed proportions). A chicken puts protein in its eggs for the same reason we need to eat protein- to provide amino acids to build proteins for the embryo.  In other words, the developing chick will get amino acids out of that yolk and white, then uses those amino acids to build the proteins it needs for muscles, bones, enzymes, hormones, etc.

Complete proteins include meats, eggs, dairy, soy, and quinoa.

2.    Incomplete protein       
This is a protein in food that is missing enough of one or more of the essential amino acids needed for the building of protein in the body's cells.  Typically these are plant proteins.

Incomplete proteins include most plant foods like grains, vegetables, nuts, seeds, and legumes or beans.

As you can see above protein is found in a variety of foods.  Below you can see the food groups and about how much protein is provided per serving.  Any whole food is going to have some protein.  Refined foods like concentrated fats and sugars will not provide any protein.  Meats are going to be the best source of protein, partially because of the portion.  If someone was to eat 3 oz. of meat (about the size of a deck of cards) they would be getting approximately 21 grams of protein.





3.    Mutual Supplementation of Proteins-

Mutual supplementation is when 2 incomplete proteins are combined to form a complete protein.  For example combining a legume and grain, like beans and rice.


 

In the illustration above the orange squares represent what essential amino acids legumes and grains are high in, and the white squares represent what essential amino acids they are limited in.  If you were to simply eat grains and no other foods, you would develop a protein deficiency, since your body would not have all the essential amino acids needed to build body proteins.  However, if you were to combine grains with legumes, you would be getting all the essential amino acids you need.   We call this mutual supplementation. 
 

A good example of Mutual Supplementation would be a bean burrito.  The tortilla would be a grain source and the beans would be the legume.

Another example of Mutual Supplementation would be split pea soup & cornbread, as split peas are legumes.

 
Green beans with a dinner roll would be a poor example of Mutual Supplementation because the green beans haven't had much time to manufacture protein the way a kidney bean would.  Green beans are more similar to a vegetable than they are a legume, and vegetables are not as rich in protein as are legumes.

The oatmeal & milk would be a fine way to get protein, but is NOT an example of Mutual Supplementation because the milk has complete protein and Mutual Supplementation involves 2 incomplete proteins.


V  Problems with Protein Quantity

A.     Problems with high protein levels in your diet:     
1.    Amine group (the N part) of extra amino acids:
Below is aspartic acid, an amino acid we looked at earlier when we said all amino acids have 4 parts.  One part is the amine group and the other 3 parts have carbon (1- Central C & H, 2-acid group (COOH) & 3- side chain). First the amine group.

Aspartic Acid

     
When there is a high dietary intake of protein, the body will rely more on this protein as an energy source.  When protein is going to be used for energy the amine group (NH2) is removed from the amino acid and the liver incorporates (NH2) into urea which is then excreted by the kidney.  In a sense protein is not a clean burning fuel, and has some waste that is created when used as a fuel source. This waste removal may be hard on the liver and kidneys, especially in someone who has compromised liver or kidney function.  
     
2.    Central C & H, acid groups (COOH) & side chains (mostly C, H, O)
are used for energy if you need it OR if the calories are extra, it is changed into fat.
     

3.  A high protein diet is not good for the heart, if the dietary choices are high in both saturated fat and cholesterol.  I had a student keep food records for his diet analysis project when he was doing the Atkins diet, and he was eating 45% of his total Calories from fat, 20% of those Calories from saturated fat, and almost 1,500 mg of cholesterol.  Most of this saturated fat was predominately coming from red meat.  If you remember from the lipid chapter last week, these numbers are well above the recommendations for a heart healthy diet.

4. Environmental Problems

Video Clip: The Hidden Costs of Hamburgers

approximately 8 minutes

Link to above video:  http://youtu.be/ut3URdEzlKQ 


(Next week you will look at a resource in Lecture 7B that will list where in Lane County you can purchase grass-fed beef, and other local more sustainably produced products.)

B.  Protein Deficiency: Global Hunger

Since the first cells to suffer from protein deficiency are those that are replaced most often, including red blood cells, plasma proteins as well as inner and outer skin cells (epithelial tissue), you would expect early symptoms to be problems affecting

blood (anemia- not enough hemoglobin to adequately transport oxygen)
the digestive tract since it's inner "skin" (poor absorption)
outer skin (scaly and dry)

Protein deficiency usually happens when someone isn't getting enough food, so that means they ALSO aren't getting enough calories and they have something called PEM or Protein Energy Malnutrition.  There are two forms of PEM.
The protein deficiency part is called kwashiorkor, a beautiful word from Ghana in Africa  that means "the evil disease that strikes the first child when the second child is born.  In other words, weaning.  It is possible to nurse 2 children, but it takes a well-nourished mother to do it.

When the child is weaned a mother who is very poor can probably manage just a thin cereal to feed her first child (incomplete protein source).  The child may get barely enough calories, but not enough protein.  That's the situation below for the child below who has kwashiorkor.  Notice the edema (fluid buildup) at the ankles and wrists as well as the skin problems.  Remember, plasma proteins help keep fluid in the blood vessels.  If there is not enough protein to synthesize plasma proteins, the fluid in the blood vessels leaks into tissue space and accumulates.  On the right is the same child once protein was added to his diet.
01kwashiorkor
With marasmus, shown below with the girl with anorexia nervosa, all nutrients are insufficient due to insufficient calorie intake.

02marasmus

The mother shown below seems to have a deficiency of calories (Marasmus) and the child a deficiency of protein (kwashiorkor).  Notice the abdominal edema (called ascites) in the child.
03pcmsudanmotherson

Click here for Part 2 of LECTURE 6A.