What are Complimentary Proteins?

Before getting to the question of complimentary proteins, we should review complete and incomplete proteins and essential and nonessential amino acids first.

Essential amino acids are the amino acids that must be obtained from the diet.  The body cannot produce these with the use of other amino acids or components at all or in sufficient quantities to meet its needs.  There are nine amino acids considered “essential”:  histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Nonessential amino acids are those which are not necessary to be obtained through food.  Nonessential amino acids can be synthesized in the body from other food components.  Other amino acids supply the nitrogen to form the amino group, and fragments from carbohydrates and fat are used to form the rest of the structure.  The nonessential amino acids may also come straight from protein sources, but it is not necessary.  The nonessential amino acids include alanine, arginine, asparagine, aspartic acid, cystine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine.

There is yet another category of amino acids known as conditionally essential amino acids.  These amino acids are normally nonessential, however, must be supplied by the diet in special circumstances when the need for the amino acid exceeds the body’s ability to produce it.  For example, as you see above, tyrosine is a nonessential amino acid, which is made from the essential amino acid, phenylalanine.  If the diet fails to contain adequate amounts of phenylalanine, or if the body cannot make this conversion for some reason, such as the inherited disease phenylketonuria, then tyrosine now becomes conditionally essential and must be obtained from the diet.

Complete proteins are protein sources which provide all essential amino acids in adequate amounts for human use.  Examples of complete proteins include sources from animals (meat, fish, poultry, eggs, and dairy) and soy.

Incomplete proteins are lacking in, or are low in one or more essential amino acids.  Incomplete proteins come from grains, legumes, and vegetables.

And finally on to this month’s question:  What are complimentary proteins?  As you see above, incomplete proteins are not considered “complete” because they are lacking in sufficient amounts of essential amino acids when consumed alone.  However, when paired with another incomplete protein or a complete protein, the result yields a complimentary protein that provides all essential amino acids in sufficient quantities in order to support health.  The pairing of incomplete protein foods, like beans (the legume) and rice (the grain) is a common example.  Look below for other complimentary protein pairing ideas:

  • Peanut butter on wheat bread
  • Peanut butter with oatmeal
  • Macaroni and cheese
  • Hummus with pita bread
  • Grilled cheese sandwich
  • Tofu and stir-fried vegetables with rice
  • Whole grain cereal with soy milk
  • Brown rice and black bean burrito
  • Yogurt with nuts
  • Lentil soup with whole grain bread
  • Pizza
  • Lasagna