Protein

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Barb Rogers

Proteins are macromolecules. They are constructed from one or more unbranched chains of amino acids; that is, they are polymers. A typical protein contains 200–300 amino acids but some are much smaller (the smallest are often called peptides) and some much larger (the largest to date is titin a protein found in skeletal and cardiac muscle; one version contains 34,350 amino acids in a single chain!).

Every function in the living cell depends on proteins.

• Motion and locomotion of cells and organisms depends on contractile proteins. [Examples: Muscles]
• The catalysis of all biochemical reactions is done by enzymes, which contain protein.
• The structure of cells, and the extracellular matrix in which they are embedded, is largely made of protein. [Examples: Collagens] (Plants and many microbes depend more on carbohydrates, e.g., cellulose, for support, but these are synthesized by enzymes.)
• The transport of materials in body fluids depends of proteins. [blood]
• The receptors for hormones and other signaling molecules are proteins.
• Proteins are an essential nutrient for heterotrophs.
• The transcription factors that turn genes on and off to guide the differentiation of the cell and its later responsiveness to signals reaching it are proteins.
• and many more — proteins are truly the physical basis of life.

Different Kinds of Protein

Protein from animal sources, such as meat and milk, is called complete, because it contains all nine of the essential amino acids. Most vegetable protein is considered incomplete because it lacks one or more of the essential amino acids. This can be a concern for someone who doesn't eat meat or milk products. But people who eat a vegetarian diet can still get all their essential amino acids by eating a wide variety of protein-rich vegetable foods.

For instance, you can't get all the amino acids you need from peanuts alone, but if you have peanut butter on whole-grain bread you're set. Likewise, red beans won't give you everything you need, but red beans and rice will do the trick. The good news is that you don't have to eat all the essential amino acids in every meal. As long as you have a variety of protein sources throughout the day, your body will grab what it needs from each meal.

1 gram of protein = 4 calories

Utilization

• Protein is used for building, maintaining and repairing muscle, skin, blood, and other tissues
• energy takes priority over tissue building
• Very little protein is used as fuel when caloric supply is adequate
• The best fuel choices are carbohydrates and fats
• If carbohydrates are not adequate, protein can convert to carbohydrates via gluconeogenesis
• Nitrogen excretion does not rise following physical activity when carbohydrates are adequate.
• Protein contains nitrogen

Best Sources

• Eggs, milk, fish, and meat
• Certain vegetable proteins can be eaten together or with animal proteins to compliment proteins for proper amino-acid ratios
• Beans
• High in lysine, low in methionine
• Soybean are the exception
• Grains
• High in methionine, low in lysine

Requirements

• Average consumption for U.S. is 100 grams/day
• Protein requirements
• 10% to 20% of the diet should be protein for sedentary individuals
• 40 grams/day for females
• 55-70 grams/day or 0.8 grams/kg body weight for males
• Recommended protein intake for athletes or physically active people (Paul 1989)
• Protein and carbohydrate requirements increases
• more calories
• ratio of protein to carbohydrates does not change
• 20% of the total calories (some diets are as high as 40%)
• Increases during an increase or change of training
• Surprisingly protein requirements for endurance athletes are greater than weight trained athletes
• Protein requirements increase when calories are insufficient

How to Calculate Your Protein Needs:

1. Weight in pounds
2. Weight in lbs x 0.8-2.0 gm/lbs = protein gm.

Use a lower number if you are in good health and are sedentary (i.e., 0.8). Use a higher number (between 1 and 2.0) if you are involved in consistent and intense weight or endurance training.

Calculating Protein as a Percentage of Total Calories

Another way to calculate how much protein you need is by using daily calorie intake and the percentage of calories that will come from protein. To do this, you'll need to know how many calories your body needs each day.

After you've figured out your maintenance calories, next figure out what percentage of your diet will come from protein. The percentage you choose will be based on your goals, fitness level, age, body type and metabolic rate. Most experts recommend that your protein intake be somewhere between 15 and 30%. When you've determined your desired percentage of protein, multiply that percentage by the total number of calories for the day.

1. Choose a calorie factor that describes your activity level:

                                      Men             Women

Very Sedentary              15                   13

Sedentary                       16                   14

Moderatly Active            17                   15

Active                             18                   16

Super Active                   19                    17

2. Determine your total daily calorie need:

____________lbs.      X         _________________    =   ____________

desired weight                         cal. factor                            cal./day

3. Then multiply .2 (20% of calories as protein) to determine how many grams of
protein you need each day:

______________   X  0.2 (percentage)  =   ____________________

cal./day                                                        grams of protein

4. And last, decide how you want to split up this total daily protein for different meals during the day.

Breakfast     AM Snack    Lunch    PM snack    Dinner    Eve Snack

___grams  ___garms   ____grams  ___grams  ___grams  ___grams

No matter what your calculations are, remember that there are no magic foods or supplements that can replace the right training and the right diet. The foundation of any program, whether your goal is to lose weight or gain muscle, is a combination of strength training and a healthy diet that includes carbs, with a balance of protein and fat.

It is clear that athletes need to consume more protein than the current USRDA for 0.8 g/kg/day in order to maintain nitrogen balance. Conversely, since the requirements of carbohydrates, and overall calories also increase with physical activity, the recommended proportion of calories from protein does not change significantly. With a calorie sufficient diet, protein requirement values needed to maintain positive nitrogen balance of both weight trained and endurance trained athletes constitutes intakes of 12% to 20% of total daily calories.

The brave man is not he who does not feel afraid, but he who conquers that fear.Nelson Mandela

Protein