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Complete Vs. Incomplete Protein Sources

By Nate Morrow / March 7, 2018

Delving into the world of fitness and nutrition, it’s easy to be overwhelmed by talk of nutrients. The one you inevitably end up hearing about – a lot— is protein.

But what is it? You’ve probably heard or read about it as a big part of building muscle, but there are some other important and often-overlooked aspects of the different protein sources that you may not know.

Let’s start with the basics…

What Is Protein?

One of the three macronutrients your body needs to function properly (along with fats and carbohydrates), proteins are primarily important for tissue growth and repair, but also necessary for digestion, metabolism, and the production of antibodies to fight infection. Comprising 10% of your brain and 20% of your heart, liver, and skeletal muscles, protein is obviously key to maintaining a strong, healthy body. What you may not realize, however, is how important it is for a healthy mind.

When you digest protein, it’s broken down into its component amino acids, which are then reassembled into 50,000 different forms your body can use for things like hormones, enzymes, and neurotransmitters. Not only do these amino acids form the building blocks of your brain’s neural network and have significant impact on your mood and brain function, but are especially important in infants’ developing brains.1 Specifically, the protein neurexin, is responsible for directing new nerve cells to their correct locations in the brain where they form their initial connections.

Complete vs Incomplete Protein Sources

Your body needs 22 different types of amino acids to function properly. Adults can synthesize 13 of those within the body (known as non-essential amino acids), but the other 9 must be obtained from food (known as essential amino acids). It’s these essential amino acids that derive the classification of protein as either complete or incomplete.2

Complete Protein Sources

Complete proteins are those that contain all essential amino acids in sufficient quantity – these are typically animal-based proteins, but a few plant sources are also considered complete. A few examples are (* indicates plant-based):

  • Meat
  • Fish
  • Dairy products (milk, yogurt, whey)
  • Eggs
  • Quinoa*
  • Buckwheat*
  • Hemp and chia seed*
  • Spirulina*
  • Incomplete Protein Sources

    Incomplete proteins are those that don’t contain all 9 essential amino acids, or don’t have sufficient quantities of them to meet the body’s needs, and must be supplemented with other proteins. These include:

  • Nuts & seeds
  • Legumes
  • Grains
  • Vegetables
  • Just because they are incomplete doesn’t make them inferior, though, they just need to be combined to provide the right balance of essential aminos. Proteins that, in combination, make a complete amino acid profile are known as complementary proteins. Here are a few tasty examples:

  • Rice and beans
  • Spinach salad with almonds
  • Hummus and whole-grain pitas
  • Whole-grain noodles with peanut sauce
  • Complementary proteins don’t necessarily need to be eaten together, but since your body doesn’t store amino acids for later use in protein combining, they should be eaten throughout a day’s meals.3

    Plant vs. Animal Protein Sources

    A bit of a controversy is brewing over whether animal or plant-based proteins 4 are better for you. Some nutritionists argue that humans are better suited to digesting animal proteins since they are closer to our own biological makeup and contain all the amino acids we need to survive. On the other side, many contend that plant-based proteins are healthier and animal-based proteins are not necessary if you have proper variety in your diet.5

    While animal proteins have somewhat better absorption and availability to the body (See: The Protein Digestibility Corrected Amino Acid Score), what I’ve found is that most of the arguments for either side have less to do with the proteins themselves,6 and more to do with the foods in which they are found (i.e., meats being higher in fat and cholesterol vs. grains being high in carbohydrates) and the morality of eating animals. For most people, the body handles both types of protein equally well.

    One potential problem with animal protein is that it tends to be higher in sulfur-containing amino acids, which causes increased acidity and could lead to calcium depletion as the body tries to balance out its pH level. This is typically not an issue when consumed in moderation with a well-balanced diet, however.

    The only major knock on plant protein is its incompleteness, but that is, again, easily overcome with a well-balanced diet.

    How Much Of Protein Sources Should You Eat?

    The current Recommended Daily Allowance of protein for adults is 0.36 grams per pound of body weight. This translates to 64 grams of protein for a 180lb man. Research shows that protein intakes as high as 0.8 – 1.0 gram/lb can help those individuals looking to build muscle, or retain muscle while losing fat during a resistance training program. We will cover protein requirements and absorption in more depth in other articles.

    A higher protein diet is often recommended during a fat loss program because of protein’s high thermic effect (up to 30% of calories from protein are burned off during digestion) and its ability to satisfy hunger.

    For your reference:

  • 1 cup of milk has 8 grams of protein
  • An 8-ounce container of yogurt has about 11 grams of protein
  • A 3-ounce piece of meat has about 21 grams of protein
  • 1 cup of dry beans has about 16 grams of protein
  • So How Exactly Should You Eat Your Protein Sources?

    As with so many things, the key to protein is balance. It is a vital and often-misunderstood part of our diets, but we need to remember that the quality and type of protein can be as important as how much we consume.

    Making sure you have a good combination of high-quality proteins in your diet is a good step towards a healthy body and mind.

    Are there any protein sources not mentioned in the article you like?

    Show 6 References

    1. Specific Brain Protein Required For Nerve Cell Connections To Form And Function. Science News. 2007.
    2. The Difference Between Meat, Soy, Whey, Dairy, and Vegan Types of Protein . Nutribody. 2012.
    3. Stanton, J. Does Meat Rot In Your Colon? No. What Does? Beans, Grains, and Vegetables! . Gnolls.org. 2012.
    4. Campbell, T. Animal vs. Plant Protein . Healthy Diet & Lifestyle. 2008.
    5. The Whole (food) Truth About Protein, Fat and Carbs . Thrive In 30. Vegga. 2012.
    6. Protein Myths . Fatfree. 2012.


    • Charles Palace says:

      Nice article, and from this I have some doubts; So, I can still build muscle by totally going vegan? Is it easier building muscle with animal protein. I mean i guess it's easier to chomp on a 16 oz, steak than eating like a whole bucket of almonds and spinach. Just saying.

      • Marc Perry, CSCS, CPT says:

        Hey Charles, Nate may want to chime in, but getting enough protein to build muscle from vegetables can be really tough, so yes, animal protein and dairy makes is much easier. Most studies show somewhere around 0.8-1.0 grams of protien per pound of bodyweight as a good amount for building muscle. You would probably have to eat the equivalent of a trucks worth of broccoli to get that amount, or less jokingly, a lot of complimentary protein...it's just tough to do, but it is feasible. FYI, we have a muscle building protein article coming out next month.

    • Smitha says:

      Hello Marc! This is an informative article! thank you.
      Recently I have been reading about the probable reasons for cancer development, and most doctors suggest that the consumption of food that creates an acidic environment is one of the major factors for the development and sustenance of cancers. In fact, a few websites also list that an anti cancer diet should have a minimal consumption of dairy and meat. In an attempt to lose fat and build muscle, I have increased my protein consumption (mainly dairy and meant), but I am disturbed after reading about the body pH and the effect of meat and diary in this regard. Could you please share your views on this.

      • Marc Perry, CSCS, CPT says:

        @Smitha - Wow, that's a great question and one unfortunately no PHD, MD, or any medical, or health professional could answer definitively. We don't know what the optimal anti-cancer diet is, it's that simple. With that said, I'm happy to share my opinion. I think if you do eat meats, it's ideal to focus on grassfed animals and fish. Dairy is a bit more complicated, but I would consider yogurt, which is easier to digest and when you do choose milk, choose the organic variety like Organic Valley. Finally, if you eat enough veggies and have a balanced diet, the acidity of the meet should be balanced out. Also consider lifestyle may have an impact such as stress and sleep, so minimizing stress and getting more sleep can likely be helpful.

    • Raza says:

      What about edamame? Last week I was at Trader Joe's and looked at their frozen edamame. It's only $1.29 for a 1lb bag (here in Chicago at least) and it has a TON of protein and fiber (I think 5g of protein and 3g of fiber), and probably a slew of macronutrients.

      I'm not overweight, and I do workout, but since I work in IT, I sit at a computer all day and the temptation to snack is really strong. I got a few bags of edamame and eat them at my desk.

      It probably beats the amount in brocolliI, but is it a complete source of protein? What could I pair with it to make it complete?


    • Seb says:

      Nate I know this is relevant but :

      -. Does lifting weights do anything do your growth/height?

      - The height that you would really be but you are shorter say 5 ’11 but you only become 5’8 , because,you lifted weights is that possible?

      • Marc Perry, CSCS, CPT says:

        Seb - Thought I answered this for you, you don't have anything to worry about if you lift weights. It won't stunt your growth.

    • Seb says:

      oh sorry no wonder why u hesitated because I wrote it three times this week!

      IM SO sorry

      i thought you answered my question about squats !!!

      thanks very much!!!

      When did you answer this question next time I'' be sure to not ask the same question again!

      Also thank you I can tell my brother the good news that he can lift weights because, he is twelve this is my other brother I have two and wants to lift weights

      I also want to lift weights

      THanks very much for answering my questions , I know I probably ask more then I should and you still nicely respond to my questions thanks and I 'll start to ask less questions , I don't want to annoy whenever you see the name Seb in the comments and a question with it, because, I think you are one of the best fitness expert out there!

      • Marc Perry, CSCS, CPT says:

        @Seb - thanks for the compliments. No worries. I would recommend your brother start out with pull ups, push ups, running up hills etc to create a base before he starts lifting weight. In other words, body weight workouts.

    • Miguel says:

      Nice article but I'm still confused. I purchased both Whey and Hemp - and eat both regularly throughout the day.

      But can I build or sustain muscle just eating Hemp seeds, Quinoa, get rid of the Whey??

      • Marc Perry, CSCS, CPT says:

        @miguel - you never know until you try, but many research studies point to around 1 gram of protein per pound of body weight being ideally for hypertrophy/muscle building. If you can get that much protein from sources other than whey, you should be fine.

    • Star says:

      What do the asterisks mean that are next to the quinoa,etc. Thank you.

      • Kristin says:

        Hi Star,

        The asterisk indicates that the food is plant-based.

        -Kristin Rooke, BuiltLean Coach & Managing Editor

    • Jeni says:

      Hello I am a 29year old diabetic. Doctor told me to eat low carbs low sugars, high protein diet. It's not as easy as it sounds. I feel guilty if I do eat any kind of bread. I try to substitute the bread with lettuce or other veggies. Any ideas on a very low carb bread I could have.

      • Kenneth Moss says:

        I've been diabetic for over 10 years now and the only thing that I've found that controls it without medication is the ketogenic diet. I was on insulin for several years and it makes me gain weight like crazy. The diet the nutritionist recommended was eating a lot of carbs each day balanced with protein. Terrible advice if you want to reverse it, great advice if you want to be hooked on diabetic drugs the rest of your life. If you search for keto bread you'll find recipes on you tube. It's never as good as the normal wheat bread, but you get used to it. I have about five keto cook books and the low carb food is pretty good. I have a low carb pot pie daily. Diabetes is carbohydrate intolerance. If you were lactose intolerant, you'd cut out the lactose. Same thing with Diabetes. Cutting out the carbs to only 20 to 40 grams a day is how I've kept my blood sugar normal without pills. The carbs I eat are leafy vegetables, a lot of avocados and broccoli family vegetables. Learning to eat this way prevents the diabetes which is worth it to me. It's not bad eating good fats. I've grown to love my three avocados a day.

        • Marc Perry says:

          Happy to hear you found the right balance that works for you, Kenneth.

      • Marc Perry, CSCS, CPT says:

        Hi Jeni - I'm not familiar with any low carb bread offhand, but if you do find one that you like, please let me / us know

    • Mark says:

      There are vegan bodybuilders who have nothing but good things to share usually. It's basically a lot of rice, lentil and bean protein per day.