Utah Department of Health    Women, Infants and Children

Section C: Protein -

Proteins are important for our bodies.  They help to build and maintain body tissue and regulate body processes.  Proteins provide 4 kilocalories of energy per gram of protein.  There are 20 amino acids found in protein.  Nine of these are referred to as essential because they must be consumed in the diet (body is unable to make on its own).


What is the difference between complete and incomplete proteins?


Complete proteins (also called high-quality proteins) contain all 9 of the essential amino acids.  Most animal foods are complete proteins.  Incomplete proteins (or low-quality proteins) lack significant amounts of certain essential amino acids.  Plant foods (with the exception of soybeans) are incomplete proteins.  Two incomplete food protein sources that compensate for each other’s inadequate supply of specific essential amino acids are called complementary proteins.  Examples of complementary proteins are legumes + grains or legumes + nuts and seeds.  Incomplete food protein sources do not have to be eaten at the same meal to be considered complementary proteins.  As long as they are eaten over the course of a day, they are considered complementary proteins.  Combining incomplete proteins is generally only a concern for those who do not regularly consume animal products or soy products.  Even then, protein intake will be adequate if the person simply focuses on eating a variety of plant foods including grains, legumes, nuts, seeds, vegetables, and fruits and eats a sufficient number of calories throughout the course of the day.


What causes food allergies?


If a protein from the diet is absorbed, without being completely digested, an allergic reaction may occur.  The body recognizes the absorbed protein as a foreign substance by the immune system, and launches an attack.  Symptoms of food allergies may manifest themselves in the respiratory system, skin, nervous system, urinary tract or digestive system. Allergies are more common in people with gastrointestinal disease and immature gastrointestinal tracts (infants).





What happens if I don’t get enough protein in my diet?


If too little protein is consumed, a deficiency occurs.  Though no longer common in the United States, protein energy malnutrition is a serious nutritional problem world wide.  Protein energy malnutrition (PEM) is classified as Kwashiorkor or Marasmus.


Kwashiorkor (moderate energy deficit, protein intake insufficient)

Physical characteristics:  bloated belly


Marasmus (energy and protein intake are inadequate)

Physical characteristics:  severe wasting


Dietary Reference Intake for protein:



Percent of total energy intake










The RDA for protein for adults is 0.8 gram of protein per kilogram of body weight.


Times of increased need:

1st 6 months of life (2.2 g/kg)

6 months – 12 months (1.6 g/kg)

Pregnancy (additional 10 – 15 g/day)

Lactation (additional 15-20 g/day)



Last edited 5/2011.