What is an “Incomplete” Protein?

beans

image: howtogrowfreshvegetables.com

This is a guest blog post by Claire Harrison

I’ve begun to look more closely at beans. Now bean protein is considered an “incomplete” protein.

I don’t know about you, but I’ve never really understood the term: incomplete protein. I know we have to “complete” the protein with other food, but what does that mean, and how are we supposed to do it?

Clearly, it was time to do some research, and here is what I learned.

There are 9 essential amino acids that come only from food.

Your body contains thousands of different proteins that have different metabolic functions. However, all proteins are molecules that include the same amino acids. It’s the arrangement of these amino acids that determines the type and function of a protein.

Your body can make many of these amino acids on its own, but not all. The nine essential amino acids that come from food and their main purposes are

  • Histidine—physical and mental growth
  • Isoleucine—muscle production, blood formation
  • Leucine—growth hormone production, tissue production and repair
  • Lysine—bone development, hormone production
  • Methionine—digestion of fats, removal of plaque
  • Phenylalanine—brain processes and mood
  • Threonine—monitoring of body proteins
  • Tryptophan—mood, pain, and sleep regulation
  • Valine—muscle production

The proportion of these 9 essential amino acids in a food determines whether it is “complete” or “incomplete.”

The “complete” or protein-rich foods: Certain foods contain the nine amino acids in a balanced ratio that enables your body to access them. Another way to put this: these foods deliver the protein to you immediately—in “one bite,” so to speak.

Meat, poultry, fish, eggs, and dairy fall into this category as well as plant products made from quinoa and soy.

The “incomplete” or less protein-rich foods: The plant-based foods—legumes, whole grains, nuts, seeds, fruits, and vegetables—also contain all the essential amino acids.

However, they have a low amount in one or more of these amino acids. For example, lentils have a low amount of methionine, and brazil nuts have a low amount of lysine.

This lower amount or “limiting amino acid(s)” creates an imbalance that limits the ability of the food to make its other amino acids available to you. To put it another way, you cannot get the protein in “one bite.”

Your body creates a nutrition resource—an “amino acid pool”—from the food you eat during the day.

Let’s say you eat rice cereal in the morning, salad at lunch, and legumes at dinner. Your body “pools” together the various essential amino acids from these foods and uses them, as needed, to create proteins.

In other words, you do not have worry about creating the right balance of essential amino acids at any one meal. Your body handles the “balance-making” for you.

The moral of the story: Eat a wide variety of non-processed, plant-based foods.

Your body does the nutrition work for you, but you must give it the tools to get the job done.

Highly processed foods, e.g., potato chips, and the “white” foods, e.g., white bread, are not good tools because they have been stripped of many good nutrients.

To get the most efficient, effective use of the amino acids stored in your body, make sure your diet includes beans, whole-grain cereals and breads, sweet potatoes, brown rice, nuts and seeds, and fruits and vegetables.

Helpful links for more information:

  • The Savvy Vegetarian: A good overview of this subject along with a helpful chart of complementary foods.
  • Self Nutrition Data: This website displays the amino acid proportions for individual foods.

After a career as a communications consultant and university instructor, Claire Harrison has turned to blogging about food and recipes for gluten-sensitive, lactose-intolerant people who must also diet for health reasons. Read her Food ReFashionista blog.

 

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  • Homecookedhealthy

    Claire, interesting article.  I do wonder more and more about the whole grains though.  After lots of research it appears that much of the grains, even the whole grains do not have the actual nutrional value that they used to due to the GM.  The actual end grain is so much different that our bodies don’t really get a lot of nutrition from this.  Have you seen of these studies?  Just learning about them myself and would love to hear your opinion.

    • Claire

      Hi, I’m glad you enjoyed the post, and you’ve asked an interesting question. I haven’t seen the studies although I have heard about the issue. Certainly, increases in gluten-intolerance suggest that GM changes to wheat have created a indigestible product for some people, me included!

      However, your question raised two further questions in my mind about the research.1) When was the food’s nutrition info determined? As I understand it, our knowledge of a food’s nutrients come from the Nat’l Nutrient Database at the US Dept. of Agriculture. But the info in this database doesn’t say when a nutrient profile was created – recently? last year? 10 years ago? I’m not sure how to find that info out. To make the claim of food not being as nutritious, researchers would need to compare its profiles from before GM and after GM. 2) What do we know about digestion now that we didn’t know before? Because of better ways of “seeing” into the body and better tools for scientific measurement, researchers know a lot more about food and body interactions than they knew, say, 25 years ago. It seems to me that this knowledge would also affect scientific decisions about food value. For example, 25 year’s ago Food X contains an enzyme known to to increase brain function, but now researchers can measure liver function more accurately and have discovered that the enzyme in Food X is not as well digested as previously thought so it isn’t as effective. In other words, the earlier claims of Food X’s “goodness” were based on less information.So…my opinion. I do think that the industrialization of our food has changed the way we eat and what we eat, and not for the better. As to whole grains, specifically? I think I’d have to see the studies to see how these problems were resolved. Hope this helps. Claire

    • Claire

      Hi, I’m glad you enjoyed the post, and you’ve asked an interesting question. I haven’t seen the studies although I have heard about the issue. Certainly, increases in gluten-intolerance suggest that GM changes to wheat have created a indigestible product for some people, me included!

      However, your question raised two further questions in my mind about the research.1) When was the food’s nutrition info determined? As I understand it, our knowledge of a food’s nutrients come from the Nat’l Nutrient Database at the US Dept. of Agriculture. But the info in this database doesn’t say when a nutrient profile was created – recently? last year? 10 years ago? I’m not sure how to find that info out. To make the claim of food not being as nutritious, researchers would need to compare its profiles from before GM and after GM. 2) What do we know about digestion now that we didn’t know before? Because of better ways of “seeing” into the body and better tools for scientific measurement, researchers know a lot more about food and body interactions than they knew, say, 25 years ago. It seems to me that this knowledge would also affect scientific decisions about food value. For example, 25 year’s ago Food X contains an enzyme known to to increase brain function, but now researchers can measure liver function more accurately and have discovered that the enzyme in Food X is not as well digested as previously thought so it isn’t as effective. In other words, the earlier claims of Food X’s “goodness” were based on less information.So…my opinion. I do think that the industrialization of our food has changed the way we eat and what we eat, and not for the better. As to whole grains, specifically? I think I’d have to see the studies to see how these problems were resolved. Hope this helps. Claire

  • http://www.facebook.com/profile.php?id=719171113 Jasona Marta

    One point in your article creates a question for me: 
    Your body “pools” together the various essential amino acids from these foods and uses them, as needed, to create proteins.In other words, you do not have worry about creating the right balance of essential amino acids at any one meal. Your body handles the “balance-making” for you.This doesn’t quite make sense to me and I’m wondering if you have any resources you can cite to expand on this… To me, digestion is taking place every moment you put something into your mouth. What I interpret here is that my body is pooling all the food I eat all day and then processing it when? Although we may not have to worry about creating balance, wouldn’t it be more effective to eat more of the foods that are already completely protein-balanced? Like chia, hemp, spirulina, buckwheat, amaranth and others not mentioned in your article?I’m not trying to start an argument or anything… just looking for a little justification so I can learn and be able to further educate my clients and customers. Thanks a bunch!

  • http://www.facebook.com/profile.php?id=610808592 Elizabeth Sophie

    Hi Claire,

    Thank you for this useful information! Would it be possible for you to share the scientific references you utilized to describe the amino acids’ main purposes, and the “amino acid pool” info? Thank you!

    Liz

  • http://www.facebook.com/rachel.terlau Rachel Terlau

    Thank you for this informative article.  Like another commenter below, I’m also confused on the “pooling” affect that supposedly occurs when consuming incomplete proteins throughout the day. I realize this is the claim made my a number of reputable vegans/vegetarians who do not consume animal proteins. However, i’ve not yet been able to grasp this concept in terms of how it occurs molecularly. If you could please provide some references to this fact which would further my personal research, I would really appreciate it! In my understanding, it is when you couple certain foods (say legume and brown rice) together in any given meal which creates the complete protein, but not at varying meal times throughout the day. Any help on this is greatly appreciated!

  • The Food Refashionista

    Dear Elizabeth, Rachel, and Jasona,

     

    Thanks for your comments. 
    First, please let me say that I’m not an organic chemist or molecular
    biologist. If I were, I’d have had a completely different life, I’m sure! I did
    try to read some articles on the chemistry of amino acids but gave up quickly.
    It was well beyond me and, I figured, my readers.

     

    Here’s the issue I primarily wanted to address: I eat very
    little complete protein. Do I have to worry about mixing the right things at
    every mealtime?

     

    What I learned was that in her book, Diet for a Small
    Planet, Frances Lappe started the idea of mixing the right foods together at one
    meal to get protein, but this notion was later proven to be false. In fact,
    some people say that the terms “incomplete” and “complete” protein is outdated.

     

    In doing my research to answer my question, I avoided all
    non-medical sources such as fitness and well-being web sites. Other than the
    Savvy Vegetarian, which seemed to provide a good summary, I also avoided
    vegetarian sites as their authors might pick and choose from the research.

     

    So I read through a number of “for-non-professional” sites
    on medical information, including

     

    ·     
    http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/protein-full-story/index.html

     

    ·     
    http://www.nlm.nih.gov/medlineplus/ency/article/002467.htm

     

    ·     
    http://goaskalice.columbia.edu/complete-and-incomplete-proteins-grains-and-vegetables

     

    ·     
    http://www.ajcn.org/content/59/5/1203S.full.pdf

     

    The idea of “pooling” came from the “storage” concept in the
    Savvy Vegetarian article. Since I couldn’t make heads or tails out of the
    molecular biology, it seemed to me that the idea of “pooling” helped make sense
    out of the complexity. But from your comments, I think the term was misleading.
    I needed another metaphor to explain that somehow, during digestion, the right amino
    acids in our blood streams get to the right cells to create the right
    amino-acid combinations (proteins) that the cell needs. Perhaps a “bus full of
    amino acids?” J

     

    I hope this satisfies… Claire

  • Tamara

    Well, you can ditz around “completing” and “pooling” and generally farting around worrying over amino acids or you can just wise up and consume some dairy, some meat, some eggs. Brain food that tastes good and is good for you. Good common sense (unless your brain is so far gone from starving on incomplete proteins you can’t think straight anymore).

  • Jennie

    Oh, for Christ’s sake eat a little dairy or meat or eggs to get enough protein to keep your stupid-assed vegetarian pea brains from shriveling like raisins. God damned stupid vegan asswipes starving themselves and their children. That will guarantee vegetarian families will only become dumber and dumber. Darwin will claim your foolish souls for the good of the gene pool. Stupid fucking foodies.

    • M.N.

      Wow Jennie, I’m not even a vegetarian and yet I was offended by your comments.
      I think you could’ve easily gotten your point across without all the swearing.

  • Suzielouwho

    The concept of “incomplete” and “complete” protein has been out of the academic and vegetarian circles for more than 15 years.  How about losing the “communication” experts and using some real bonafide, degreed nutrition experts!!

  • Barb

    For what it’s worth, I thought your post clarified sometime I’ve also been confused about but hadn’t bothered to research.  There’s a reason why scientist need communicators! Thank you.

  • Christopher

    I would suggest the blog post by CH is incomplete. My background includes a PhD in Nutrition Science and 10 years of teaching Human Nutrition to undergraduates (and 30 years of following a vegetarian diet). I usually spend more than an hour lecturing on this topic to explain it, but I will spare you most of the details.

    I have never seen or heard of specific roles being assigned to specific amino acids before and would be quite curious to learn where that information came from. There are thousands (millions?) of different proteins our body makes – hormones, enzymes, hair, skin, and on and on.  Most of these tend to have hundreds of amino acids in a single protein, sometimes thousands, and there are 20 amino acids that combine in various patterns – the recipe or code for the sequence of these amino acids is in our DNA. All the proteins in our body have all 20 amino acids, in different proportions, and different sequences (with the exception of a few proteins made up of small numbers of amino acids).  The idea that specific amino acids have specific roles doesn’t make much sense since all 20 amino acids are needed to make ALL the proteins in our body.

    The part about the body being able to make 11 of the 20 amino acids is correct, and that 9 must be obtained from the diet (non-essential vs. essential amino acids).

    The key to understanding this is that making proteins is much like using the alphabet to play scrabble – some amino acids are needed frequently and some less frequently. Rather than needing a specific amount of protein, we need amounts of each amino acid, in different proportions (how many E’s vs. Z’s are there in scrabble?).  The proportions of the different amino acids in animal foods are more similar to human needs….because humans are animals.  Plant proteins have ALL 20 amino acids, but they are present in different proportions.  If you are trying to make a specific protein and you are missing one of the amino acids, you can’t just skip it and finish making the protein, just like you can’t skip a letter when writing a word and finish the word. The system stops and you are left trying to make words (or proteins) that could be made without that letter (or amino acid).

    Grains tend to be low in lysine (CH used brazil nuts as an example, but grains is the more typical example given because grains are more commonly consumed than brazil nuts). Beans tend to be low in methionine and cysteine (both are related and are sulfur containing amino acids). Grains DO have lysine and beans DO have methionine and cysteine, but their proportions relative to the other amino acids in those foods are low relative to human needs.

    HERE IS THE MOST IMPORTANT POINT in all this – regarding how much protein you need for good health, and when this does or doesn’t make a difference that you should be concerned about. All of this makes a difference IF your protein consumption is low. If your body needs 40 grams of protein/day, with the amino acids in just the right proportion, and you eat just 40 grams of protein today of ONLY grain protein or ONLY bean protein, you would NOT meet your requirement for the day. Even though the total AMOUNT of protein would be what you needed, the proportion/distribution of specific amino acids wouldn’t be what you need.

    40 years ago when Frances Moore Lappe wrote Diet for a Small Planet, the idea was promoted that eating grains and beans at the same time COMPLEMENTS the proteins (grains have relatively high proportions of the amino acids limiting in beans, and vice versa). The idea was the complementing the proteins this way made up for “incomplete proteins”.

    However, if you eat 80 grams of protein/day (which is typical), you’ll end up with enough of the “limiting amino acids” (CH got that term right!), and loads extra of the non-limiting amino acids that you’ll bread down and convert into fat and carbs.

    In short, vegetarians who have access to and consume a wide variety of foods are at no risk of being protein deficient. Vegans who do the same are most likely at no risk of being protein deficient. If we are talking about a growing child, that needs enough protein for maintenance AND growth it can be a different story. It can still be done, but more attention needs to be given to adequate intake.

    The Academy of Dietetics and Nutrition (formerly the American Dietetics Association) has helpful publications on vegetarian and vegan diets.

    Position of the American Dietetic Association: Vegetarian Diets, Journal of the American Dietetics Association, Volume 109, Issue 7, Pages 1266-1282 July 2009.

    Academically, the idea of “incomplete proteins” makes for an interesting class discussion and leads to an understanding of what a “limiting amino acid” is. Practically, for the vast majority of individuals in the US (and around the world), it is a moot point, because most people consume far more protein than they require (in part thanks to the myths perpetuated by certain agriculture groups for may decades – meat, dairy, eggs…a topic for another day).

    I hope that is helpful. Sorry it was so long. But, it isn’t simple.

    • 40 years in public health

       Anyone who would feed a vegetarian fad diet to a child should be hauled in by Child Protective Services. It is stupid enough to starve one’s self of essential amino acids, it is criminal to condemn innocent growing children to deliberate malnutrition. 30 years a quack, so what? Take your stupid smug vegetarian suggestions and cram them. Maybe you can digest some protein out of them that way,

    • http://www.fooducate.com/blog Fooducate

      Thanks Christopher or taking the time to elaborate on the issue.

  • Katrina Plumb

    I found this article really helpful, especially as I have recently been diagnosed with autoimmune diabetes and find a high protein, low carbohydrate diet beneficial. Could you tell me whether an egg white is a complete protein, or only when combined with the yolk?