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Protein

A Protein is a chain of linked amino acids. They have many different functions: they help build and maintain your cells; give structure, help digestion and aid movement. There are many sources both animal and plant that can be used to get the 8 essential amino acids that your body can not make itself. Eating a balanced mix of these foods with only moderate red meat and dairy is the healthy choice.

Protein
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What it is

 

Proteins are complex organic compounds made of amino acids in a chain. In general a protein contains 20 different standard amino acids in chains of varying combinations and lengths. Many of these amino acids can be made by your body, although you can not make all the amino acids that your body needs. There are 8 of these essential amino acids that must be found in the foods that you eat. You digest these foods and break down the protein from the food into free amino acids that can then be used for many vital processes and functions in the body.
 

Amino Acids Used By Your Body

 
Essential Non-essential
Isoleucine Alanine
Leucine Asparagine
Lysine Aspartate
Methionine Cysteine*
Phenylalanine Glutamate
Threonine Glutamine*
Tryptophan Glycine*
Valine Proline*
  Serine*
  Tyrosine*
  Arginine*
  Histidine*

* essential in certain cases (often age or health related)


Each protein is assembled using the genetic code in your genes having its own unique amino acid sequence to create a protein with a set purpose. Proteins are in every cell in your body, they make up a major part of your skin, muscles, glands and organs. Protein is also in all your body fluids except for urine and bile.


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What it does

 

Proteins are needed by your body to help maintain and build your cells. They are necessary for all growth and development in your tissue , skin, muscles, organs and glands. Proteins can provide structure (ligaments, fingernails, hair), help in digestion (stomach enzymes), aid in movement (muscles), and play a part in our ability to see (the lens of our eyes is pure crytalline protein). They are essential in the repair of wound and the building and recovery of muscles. Proteins are of increased importance to people during childhood, adolescence, pregnancy as well as those people who are ill or recovering from illness and those who perform strenuous physical activity.

Proteins:

  • Have structural functions or mechanical functions in muscles.

  • Are  vital in the cytoskeleton, which forms the structure that maintains your cells shape.

  • Vital in cell signaling, enabling your cell to recognize and respond to their microenvironment. This is the basis for development, tissue repair, immunity and your cells internal stability.

  • Are enzymes that are vital in metabolism.

  • Essential for immune response – antibodies are proteins used by the immune system to identify and neutralize bacteria, viruses and other foreign objects.

  • Needed for cell adhesion that enables a cell to bind to a surface, another cell and the extracellular matrix that define collagen, elastin and other connective tissue.

  • Cell Cycle - Protein is vital in the series of events leading to cell division.

 


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Where you get it

 

Proteins-containing foods are often divided into two groups: complete protein foods and incomplete protein foods. The complete protein foods contain all of the 8 essential amino acids while the incomplete protein foods are lacking one or more of those 8 essential amino acids.Complete proteins are found in animal foods while the only vegetal plant protein considered a complete protein is soybeans. 

The important consideration when choosing the foods you will eat to meet your protein needs is that it is the combination of proteins over an entire day that is important, not what is in one particular food. Plant proteins can be combined to give you a complete protein containing all the 8 essential amino acids.

Animal protein and vegetable protein probably have the same effect on your health. Red meat and dairy foods are good sources of protein although they are also very high in unhealthy saturated fat and cholesterol. Eat both in moderation, limiting meat to preferably once a week and no more that twice a week.

A 170g cooked steak is a great source of protein—40 grams worth. But it also gives you 35 grams of fat, 12 of them saturated. That's almost two-thirds of the recommended daily intake for saturated fat. The same amount of salmon gives you 34 grams of protein and 18 grams of fat, with only 4 of them saturated. A cup of cooked lentils has 18 grams of protein, but under 1 gram of fat.

Vegetal sources
• Beans and other legumes
• Seeds
• Nuts
• Grains, amarath and quinoa being the highest protein level
• A small amount is also found in vegetables

Animal Sources
• Meat
• Fish
• Poultry
• Eggs
• Dairy foods – milk, cheese and yogurt

Be aware that a diet high in meats and dairy products can be high in cholesterol and saturated fat.

 

Supplements
A nutritionally balanced diet will give you all the protein you need. Protein supplements are rarely needed by healthy people. If you are ill are recovering from a illness or disease, are an elite athlete or bodybuilder you may require more protein that that recommended. Please be sure to seek advice from a health professional before eating higher levels of protein.

There are many protein supplements on the market today. Most are used in the sports industry to build and maintain muscle mass. The quality of these types of proteins can vary greatly. If you use these products be sure to examine the ingredients to ensure it uses a high quality protein base and does not contain unwanted additives.


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Things to watch out for

Proteins in the diet and in the environment are responsible for allergies – overreactions of the immune system. By changing or limiting the types of proteins that you eat or come in contact with can greatly reduce allergy conditions. This should be done with the guidance of a trained health professional.
 
Too Little
Protein malnutrition leads to the condition known as kwashiorkor. 

Lack of protein can cause:
• growth failure
• loss of muscle mass
• decreased immunity
• weakening of the heart and respiratory system, 
• death.

Too Much
Eating a high amount of protein as in a high protein diet or in athletic training  does not seen to harm your heart and there is no good evidence that increases your risk of cancer nor does research suggest that it increases the risk of type 2 diabetes. What can increase the risk of these health problems can be the source of the protein not the protein itself. Red Meat and dairy products that are high in saturated fats and cholestrol can increase these risks. A diet high in vegetal protein and fat may in fact slightly decrease the risk of type 2 Diabetes (adult onset)

Loss of bone density and osteoporosis 
During the digestion of protein your body releases acids that are usually nutallized by calcium and other agents in the blood. Eating a lot of protein, such as the amounts that are often recommended in high protein diets, used a lot of calcium. Insufficient available calcium may cause calcium to be pulled from your bones Eating high levels of protein may not harm you bones over a short time but a lot of protein for a long time could weaken your bones.


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How much you need

To reach your health goals and become healthy the most important step is to eat a well balanced diet of food from across all the food groups. 

This list is of recommended daily amount of each food group for an average person 19 to 50 years old with a low level of exercise (30minutes of less a day). If you are older you may need a little less, if you are younger, a little more and if you are very active even more food should be eaten. For more information on serving sizes see our special feature on Sizing Up A Serve.
 
Servings per food group:
• Whole Grains (Carbohydrates):  6 – 8 
• Meat and beans (Protein):  1 – 2 
• High quality fats: 1
• Dairy:     2 – 3
• Fruit: 2
• Vegetables: 5
• Water: 6

The following are the recommended serving sizes for protein:

• 3 ounces of cooked lean meat, poultry, or fish (a portion about the size of a deck of playing cards)
• 1/2 cup of cooked dried beans
• 1 egg, 
• 2 tablespoons of peanut butter
• 1 ounce of cheese

The recommended dietary Intake** (RDI)
The recommended dietary Intake** (RDI) is the level of intake of nutrients considered adequate to meet the known nutrient needs of practically all healthy people.

Specific recommendations for each vitamin depend on age, gender, and other factors (such as pregnancy and general health). 

Recommended dietary Intake (RDI)    

Infants     
0–6 months     9.1 (g/d) (AI) Adequate Intake
7–12 months     11 (g/d)

Children     
1–3 years     13 (g/d)
4–8 years     19 (g/d)

Males 
9–13 years     34 (g/d)
14-18 years     52 (g/d)    
19–70+ years     56 (g/d)

Females
 9–13 years     34 (g/d)
14-18 years     46 (g/d)    
19–70+ years     46 (g/d)

Pregnant 
18-50     71 (g/d)
Lactating 
18-50     71 (g/d)

By far the best way to get your daily requirements of nutrients is to eat a balances diet that contains a wide variety of whole foods from all the food groups.  Note that processed foods are depleted of most of their nutrients.

**Many countries have equivalent recommendations although the RDI  is accepted throughout the world as a valid source of information. These recommendations are based in scientific knowledge and are presented by the US National Academy of Sciences, US Institute of Medicine and the US Food and Nutrition Board.
 


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References

Harvard Medical School, The Nutrition Source, Protein: Moving Closer to Center Stage  http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/protein-full-story/index.html, retrieved 05/2009

USDA – National Agriculture Library, http://www.nal.usda.gov/fnic/topics_a-z.shtml, retrieved 02/2009

US National Library of Medicine and the National Institute if Health http://www.nlm.nih.gov/medlineplus, retrieved 02/2009

University of California, Berkley, The newsletter of nutrition, fitness and self care, http://www.wellnessletter.com/index.html, retrieved 02/2009

Wikipedia, Protein, http://en.wikipedia.org/wiki/Protein, retrieved 05/2009

Institute of Medicine, Food and Nutrition Board. DIETARY REFERENCE INTAKES FOR Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academy Press, Washington, DC, 2005.

Fürst P, Stehle P Institute of Nutrition Science, University of Bonn, (01 Jun 2004). "What are the essential elements needed for the determination of amino acid requirements in humans?". Journal of Nutrition 134 (6 Suppl), http://jn.nutrition.org/cgi/content/full/134/6/1558S 

Murray, Michael T.  Encyclopedia of Nutritional Supplements,  Prima Publishing, Rocklin, CA, 1996.

Griffith, H. Winter. Vitamins, Herbs, Minerals & Supplements: The Complete Guide. Arizona: Fisher Books, 1998.

Dunne, Lavon J. Nutrition Almanac, 3rd ed, McGraw-Hill, New York, 1990.

Bratman, Steven, and David Kroll. Natural Health Bible. Rocklin, CA: Prima Publishing, 1999.

Paul Pitchford. Healing with whole food, North Atlantic Books, 2002.

Goldman L, Ausiello D. Cecil Textbook of Medicine. 22nd ed. Philadelphia, Pa: WB Saunders, 2004.

Bratman, Steven, and David Kroll. Natural Health Bible. Rocklin, CA: Prima Publishing, 1999.
 


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