The Importance of Protein in Our Diet

Protein Shake

What are proteins?

Protein is extremely important and needed for your body to be healthy and function properly. Protein is made up of amino acids, which the body must have in order to synthesize various proteins and nitrogen containing molecules that make human life possible.

Amino acids

Amino acids are the building blocks of life. There are 2 categories of amino acids, essential and nonessential.

  • Essential amino acids are amino acids that the body cannot make and we must obtain through diet.
    • Essential- leucine, isoleucine, valance, lysine, tryptophan, threonine, methionine, phenylalanine, histidine
  • Nonessential amino acids are amino acids that the body is able to make for itself.
    • Nonessential- alanine, asparagine, aspartic acid, cystine, glycine, hydroxyproline, glutamic acid, serine
  • There are also conditionally essential amino acids, which are amino acids that are normally nonessential, but under certain physiological conditions they become essential and the body is unable to make them.
    • Conditionally essential Amino Acids- Tyrosine, cysteine, proline, arginine, glutamine

Why do we need protein and how much is needed?

Dietary protein contributes to the body’s supply of amino acids that is needed to produce important molecules in our body such as enzymes, hormones, antibodies, protein transport and to serve as a buffer. Protein is also needed for the body’s growth, muscle building and repair.

It is recommended for adults to consume 0.8 gram protein per kilogram of bodyweight. For example, a 130 pound person (59 kilogram) would need 47 grams protein per day. Keep in mind, this recommendation is the amount of protein needed to prevent deficiencies for generally healthy adults.

If we take into consideration the reasons why protein is important such as enzymes, hormones, immunity, protein synthesis (the making of new proteins), weight management, satiety, muscle growth and repair, it is obvious we need more protein than what is needed to prevent deficiencies. Active healthy adults may require consuming approximately 1 gram of protein per pound of bodyweight. For those who want to gain strength and build muscle, consider taking in 1.25-1.50 gram per pound of bodyweight.

Eating more protein may improve your metabolism and lead to better weight management. The amount of energy, up to 30%, it takes for your body to digest, absorb, transport and store protein is a lot higher than it is in carbohydrates and fat. High protein foods are slow to digest and empty the stomach, which results in feeling full longer. This means there is a more steady effect on blood sugar compared to the sharp rise that results in eating simple carbohydrates. When your blood sugar rises then falls sharply, as in eating simple carbohydrates, it sends out signals that you are hungry. The more satiety you feel after a meal, the better you will be at managing your weight.

Protein quality

Complete proteins are proteins that contain all essential amino acids in the amounts needed by humans. These include all animal products, excluding gelatin, and soy protein. Quinoa is also a complete protein.

Incomplete proteins have too little of one or more essential amino acids. These are plant foods such as legumes, vegetables, cereals and grain products.

Incomplete Protein Combinations to Provide all Essential Amino Acids

For vegans, this information is important to ensure all essential amino acids are consumed daily. By eating a variety of legumes, vegetables and grain products, vegans should have no problem consuming all essential amino acids.

Protein Sources and Serving Sizes

Food

Serving Size

Protein*

Hamburger, extra lean CP

3 oz

22 g

Chicken, roasted CP

3 oz

27 g

Salmon, wild CP

3 oz

17 g

Tuna, water packed CP

3 oz

20 g

Sirloin steak, lean CP

3 oz

25 g

Cottage cheese CP

1 c

28 g

Skim milk CP

1 c

8 g

Yogurt CP

8 oz

8 g

Cheddar cheese CP

1 oz

7 g

Soy milk CP

1 c

8 g

Tofu CP

1/2 c

7 g

Mixed nuts IC

1 oz

5 g

Peanut butter, crunchy IC

1 Tbsp

8 g

Lentils, cooked IC

1/2 c

17 g

Kidney beans, cooked IC

1/2 c

8 g

Couscous, cooked IC

1 c

6 g

Spaghetti, whole wheat IC

1 c

7 g

Egg CP

1 large

6 g

Whole-wheat bread IC

2 slices

4 g

Quinoa, cooked CP

1 c

8 g

Rice, cooked IC

1 c

4 g

Kale, cooked IC

1 c

2 g

CP= complete protein, IC= incomplete protein, c=cup, g=gram, oz=ounce Tbsp=tablespoon

*Numbers rounded to nearest whole number. Source: USDA National Nutrient Database for Standard Reference.

Take home message:

  • Consume a complete lean protein with every meal.
  • Protein burns more calories to process and store than carbohydrates and fat, which can lead to a higher metabolic rate.
  • Protein causes a steady rise in blood sugar resulting in satiety and a delay in hunger. This can also result in weight loss. 
  • Complete proteins are animal products, excluding gelatin, soy and quinoa.
  • Combine incomplete proteins to make a complete protein, such as peanut butter and whole grain bread.

Sources

Gropper, S.S., Smith, J.L. and Groff, J.L. Advanced Nutrition And Human Metabolism. Belmont: Thomson Wadsworth. 2005

Mahan LK, Escott-Stump S. Krause’s Food, Nutrition & Diet Therapy. 11th ed. Philadelphia, PA: Saunders/Elsevier. 2004.

Balachandran, A.T. (Oct. 24, 2008). How Much Protein Do You Need for Muscle Growth? Retrieved from http://www.exercisebiology.com/index.php/site/articles/how_much_protein_do_you_need_for_muscle_growth/

USDA National Nutrient Database for Standard Reference. Retrieved from http://ndb.nal.usda.gov/ndb/foods/list

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