What Is A Complete Protein? Complete vs Incomplete Proteins | Ask The Fitness Nerd

[ 17 ] March 8, 2009 |



Completely Confused About Complete Proteins? Learn What A Complete Protein Is and How Balance Your Protein Intake

Dear Fitness Nerd,Picture of Complete Protein Foods and Incomplete Protein Foods

Can you explain exactly what a complete protein is? I’m 23 and pretty into fitness, working out, etc. I lift weights several times a week and run daily.  But I’m also a vegetarian and concerned I may not be eating enough protein every day to support my activity levels.  I’m also worried that since I primarily eat plant sources of protein, I might not be getting a complete protein. Can you help me out here? Thanks!   – Jessa (San Diego – CA)

A complete protein is a protein source that contains all eight essential amino acids in the sufficient proportions to support normal biological functions.   In adults, the eight essential amino acids are:

  • Phenylalanine
  • Valine
  • Threonine
  • Tryptophan
  • Isoleucine
  • Methionine
  • Leucine
  • Lysine

These amino acids are called “essential” because the body cannot make them, so they have to be supplied through diet.  Recently, histadine has been added to this list as well, as scientists discovered that adults cannot synthesize it.



Incomplete proteins are proteins that lack one or more of the eight essential amino acids. Most plant-based proteins will meet the criteria for an incomplete protein, while animal-based foods are considered the primary sources of complete protein.

Examples of Complete Proteins from Animal Sources

The most common examples of complete proteins are foods that come from animals. These sources of protein include things like:

  • Fish
  • Seafood/Shellfish
  • Poultry
  • Milk
  • Eggs
  • Cheese
  • Meat

When you consume these foods,  you take in all eight essential amino acids in a single food source. There is generally no need for additional amino acid supplementation.

Examples of Complete Proteins from Plant Sources

There are only a handful of plant-sources of protein that provide all eight amino acids in the necessary proportions to qualify as a ”complete protein.”  These sources of complete protein include:

  • Quinoa
  • Buckwheat
  • Hempseed
  • Soybeans

Most people who eat a variety of plant-based and animal-based foods typically do not have to worry about whether they are consuming complete proteins — the variety in their diet will typically take care of that naturally.

Complete Protein for Vegetarians

In terms of complete proteins for vegetarians, conventional wisdom has stressed protein combining of certain foods together in the same meal to ensure that a person is receiving adequate amounts of all eight essential amino acids.  Examples of complete protein food combinations include consuming beans and rice  in the same meal or eating corn and wheat together. 

The idea here is to combine a food that is lacking in one or more amino acids with another food that contains those missing essential amino acids.  In doing so, you create a complete protein.

However, recent research has indicated that it may not be necessary to consume complementary proteins in the same meal.  A small amount of amino acids are ”pooled” by the body  – so for most moderately active people eating a variety of plant-based proteins across the day should suffice. For very active people, athletes or even fitness buffs who are trying to add lean mass,  protein combining may be more desireable.

While protein combining may be unnecessary for the average vegetarian, there are some exceptions:  If a person is on a vegetarian diet that is heavily dependent on fruit, tubers or is high in junk food, they may not be consuming sufficient amounts of essential amino acids.  In these cases, diet modification may be necessary.

Complete Proteins and Vegetarian Athletes

While protein deficiency in vegetarians is generally rare — especially for people of average activity levels –vegetarian or vegan athletes may need to pay extra attention to the amount of protein they consume, even if the protein combinations are less important. 

Because protein requirements are typically higher in athletes or very active individuals in general (regardless of their type of diet), if you are focusing on building additional lean tissue, you may need to up your protein slightly on a plant-based diet to ensure recovery, muscle growth and support the added demands of your sport or physical activities.

Many plant-based sources of protein such as certain types of beans, pluses and grains (for example wheat) are not as easily digested as animal-sources of protein, so you may require a slightly higher RDA of protein versus a person who includes meat, eggs, milk or seafood in their diet. 

Even this is a bit controversial, since scientists continue to debate whether the Protein Digestibility Corrected Amino Acid Score (PDCAAS) accurately measures true protein digestibility in humans – especially since there are a number of variables that can influence how much protein from a food is absorbed by your body (including cooking methods, other foods consumed alongside it, your age and even flora and fauna in the gut.)

While the USDA and World Health Organization (WHO) does not differentiate between athletes and non-athletes when it comes to recommended daily allowances for protein, a good rule of thumb for endurance and strength athletes in good health is to have a protein intake of around 10 – 20% of your total calories.  

Recommended ranges are typically out  1.4 – 1.8 grams of protein per kilogram of body-weight per day, or roughly 150 grams of protein for a 180 lb male, or about 110 grams of protein for a 130 lb female.

Should I Worry About Getting Complete Proteins?

Depending on the type of vegetarianism that you follow, you may already be consuming plenty of sources of complete proteins.

Lacto-Ovo vegetarians who eat eggs and/or dairy products should have few concerns about complete proteins.  Vegetarians who only eat plants probably have little to worry about, but there are many vegetarian athletes and body builders who choose to protein combine just to be safe.

Whether this is necessary is open to debate. The belief among these individuals is that protein combining may give them a performance and recovery edge — especially immediately following weight training when complete proteins may be more vital to recovery and growth.  There is very little direct clinical research around this, however.

The research that does exist has looked not specifically at protein combining in vegetarian athletes, but rather at the use of sources of complete protein — typically whey and/or casein protein from diary products — as a post-workout recovery meal.  In these cases, individuals consuming this combination of protein and carbohydrates have shown increases in lean body mass over those who consumed only whey or carbohydrates.

The reasons for this are still open to interpretation. It may be simply that whey protein is quickly digested by the body, making it more readily available for recovery. Or it may be that consuming a complete protein itself assists with  protein synthesis. More than likely, it is a combination of the two.

If  muscle building on a vegetarian diet is one of your goals, go ahead and protein combine — especially immediately following your workouts.  It won’t hurt, and may possibly help.  While this is a bit easier and more convenient for Lacto-Ovo vegetarians, if you are on a strictly plant-based diet, you can always try soy protein isolates or grains like quinoa.

Have a Question for the Fitness Nerd? Want a Chance To Win Some Free Under Armour?

If you have a question for the Fitness Nerd on exercise, diet, nutrition or healthy eating and cooking, send your question to: [email protected]

Each month, I’ll draw a name from all of the legitimate questions I receive and the winner will receive a $20 Under Armour eGift Card redeemable exclusively at http://www.underarmour.com/.

What’s my definition of legit? Legit means that your question is related somehow to fitness, diet, nutrition, supplements, exercise, healthy eating, etc. You get the point.

Please include your full name, city and state and e-mail address to be entered in the drawing. Only your first name, last initial and location will be posted with your question. The winner will be chosen and announced on the first day of each month. Void where prohibited, you need not be present at the drawing to win, blah, blah, blah ….

Share this:
Share this page via Email Share this page via Stumble Upon Share this page via Digg this Share this page via Facebook Share this page via Twitter
If you enjoyed this post, make sure you subscribe to my RSS feed!

Tags: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,

Tags: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,

Category: Ask The Fitness Nerd, Protein

About the Author ()

Leader of the Best Internet Marketing Team in the World By Day, Fitness Nerd By Night.

Comments (17)

Trackback URL | Comments RSS Feed

  1. Jenny DiDonato (1 comments) says:

    This is a great post!  Very easy to read and very informative.

    • Matt (194 comments) says:

      Jenny, thanks for stopping by and leaving a comment. Glad you liked the article. Great seeing and hearing from one of my local Tweets!

  2. Vegetarian Bodybuilding (1 comments) says:

    Great post…real informative…will try to follow your tweets also

  3. John (14 comments) says:

    Good question, good answer. Meat is a rich source of those essential amino acids. Vegans can still get these from vegetables, but not from the common ones.
    John

  4. Melissa Bastian (1 comments) says:

    Thank you for this informative, thorough, and well balanced article!  All too often we hear that it’s just impossible to get enough protein from plants, that you just absolutely must consume high quantities of complete proteins, bla bla bla.  I’m so happy to find another source that is reiterating what I’ve been trying to explain to people for ages.

  5. Will Werner (4 comments) says:

    Your promotion to get more visitors to your website is brilliant. Making an Under Armour product as prize for the competition is an excellent way to target your audience interested in fitness. Very nice job with the article also!

  6. Isaac Gonzalez (1 comments) says:

    Does anyone have a complete list of protein foods ?–~

  7. Deann Chavous (1 comments) says:

    Nice site. I always train hard at least three times a week and following a tough session your body wants the best quality protein to fix you for your subsequently workout. I at all times go for lean protein as the best muscle building food, essentially poultry, turkey in addition to fish. I also have scrambled egg whites for breakfast.I usually combine these meals with a complex carb as well as veg as well. I keep away from protein shakes because I see them as a waste of money, the body is designed to digest food and drinks lack the thermic affect of foods.

  8. Mitch Hell (1 comments) says:

    I think this topic is very important. As a trainer myself, most people don’t understand this! Good info, keep it up!

    Mitch Hell

  9. david miller (1 comments) says:

    Very helpful.  My trainer has been mentioning ‘complete proteins’ and I didnt want to appear an idiot and ask what it meant.  Now I know, better informed in my day ;-)

  10. Dany (1 comments) says:

    According to your post, you said the essential amino acids needed to be a complete source of protein are Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Leucine, Lysine, and Histidine.  Aren’t  bananas, spinach and many other plant base protein complete source of protein?  According to nutritiondata.com all the essential amino acids are found in fruits and vegetables.  What do you think?

  11. sadz saeed (1 comments) says:

    Hi Matt recently I’ve read loads of your blogs about the exercise tips about how to loos weights, how to perform correct exercise and etc etc.. so I’ve got a question can you advice me which protein shake is best for women’s to take which helps them to lose weight, contain the entire vitamins  and minerals and also help to grow hair… cos I’ve noticed when ever i go on healthy eating diet and exercise on regularly basics i tended to lose lots of hairs… so pls pls can you help me and answer my question..  

Leave a Reply

Comments links could be nofollow free.