Complementary Proteins: Getting Enough Protein on a Plant Based Diet


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It’s a common misconception that it is extremely difficult or impossible to eat enough protein to maintain or build muscle mass on a plant-based diet, but with a little education and coordination this isn’t unachievable. In fact it really isn’t even that complicated. This post will be discussing basic strategies to get enough protein from plant-based sources.

Let’s start with breaking down protein. Amino acids (AA) are the building blocks of protein. Protein is made up of amino acids linked together. There are 20 different amino acids, and our body can create most of them from other nutrients and other amino acids. Only 9 of these proteins are considered “essential amino acids” because they are the amino acids that are essential for us to obtain in the diet since we cannot create them ourselves (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine – arginine is a conditionally essential AA if we are in a metabolically stressed state). There are tons of plants that contain most, but not all, of these amino acids in sufficient amounts to support our metabolic needs. Luckily for us, there are also plenty of plant foods that complement each other’s amino acids. These are called Complementary Proteins. 

Complementary Proteins: Foods that individually do not contain all essential amino acids, but when eaten together provide the entire range of all 9 essential amino acids that the other is missing in adequate amounts, creating a Complete Protein source.

To make it simple, the basic principle of combining complementary proteins into one meal is to put together foods from 2-3 of these categories: Whole grains, Beans & Legumes, Nuts & Seeds

You can tell a food is a whole grain if it is declared on the package with this symbol, or you can take a look in the ingredients to see if it is listed as a “whole grain”.

Image result for whole grain stamp

Some of the common whole grains include corn, rice, oats, quinoa, barley, sorghum, spelt, rye, and wheat. These usually make a great base for your dish. Lysine is the limiting amino acid in this food group, meaning your body’s ability to get a complete protein out of this is limited by their lack of lysine.

Our next category – Beans and legumes – can make up for this! This foodgroup is often lacking in the methionine and cysteine that whole grains provide, but it brings lysine to the table that the whole grains lack, so that’s how they balance out to provide a “complete protein”. There are tons of different beans that I’m sure you’re familiar with – black beans, kidney beans, cannellini beans, navy beans, you name it, pretty much all of these beans are great to add in. Soybeans are particularly useful since they are considered to be a complete protein themselves, they come in the form of tofu, tempeh, miso paste, edamame, and obviously soy milk, too. Chickpeas, lentils, and peas also make up this group. I have noticed that pea protein is gaining in popularity, which is exciting to see.

Finally, we have Nuts & Seeds. These can be eaten in between meals as a snack, sprinkled on top of dishes, baked into recipes, or mixed in as nut butters. Some examples of these would be hemp seeds, pumpkin seeds, sunflower and sesame seeds (which I personally like to mix in as tahini), peanuts, almonds, pistachios, cashews, walnuts, hazelnuts, pine nuts, pecans, and the list goes on.

Virtually all plants have some amount of protein in them, though these three categories have them in the highest amounts. Different vegetables may contribute more protein than others. 

Here are just a few of the infinite combinations that you could create just to get you started. I’ve included the nutritional value, but obviously depending on the brand that you use these could vary. For reference, 1 oz of cooked meat is approximately the size of 3 dice or the size of your thumb and has about 7 grams of protein:

  • 2 TBS Peanut butter on 1 slice whole wheat bread = 11 g protein. I like to add hemp seeds to mine.
  • 2 TBS Peanut butter with ½ cup oatmeal (dry oatmeal, it will be more after cooking) = 12 g protein. I also add hemp seeds and walnuts into mine, cooking it with soy milk instead of water can also increase protein content
  • 4 TBS Hummus with 1 large whole grain pita bread = 15 g protein
  • 3 oz Tofu and ½ c stir-fried vegetables with ½ c rice = 12 g protein
  • ½ c Whole grain cereal with 1 c soy milk = 11 g protein
  • 1 c Brown rice and ½ c black beans in 2 corn tortillas = 14 g protein
  • ½ Lentils in 1 c tomato soup with 10 whole grain crackers = 16 g proteinThose are all extremely simple combinations, the more you add the more protein you get, there is seriously no end to the combinations you can come up with

Example: Say I need 50 g of protein a day. If I start my day with peanut butter and oatmeal or peanut butter and toast, which is pretty typical, then added my daily coffee with 1 cup of soy milk, a midday snack of mixed nuts containing cashews, almonds, and peanuts (about 3 ounces), then had a lunch of stir fried rice, tofu, and broccoli, and finished it off with a bean, rice, and veggie burrito in 3 whole grain corn tortillas, I would have gotten about 68 g of protein, well over what I need for the day.

o   (This is equivalent to 9.7 ounces of meat)


It is not necessarily essential for you to eat these foods at the exact same time. If you eat a good variety throughout the day, you are still getting in those essential amino acids and when they are eaten within the same time frame your body can still use those essential amino acids to complement each other and create that protein.

A huge added benefit of obtaining your protein through entirely plant-based sources is that while animal proteins do not contain fiber, virtually all plant based protein sources are sources of fiber which is a huge supporter of healthy gut bacteria and the microbiome (see my previous post on this topic here). 

A common misconception is that with all of the emphasis placed around protein these days we perceive that we need way more of it than we actually do and that animal products are the only way to get enough. This leads us to believe that we need to eat meat at every meal and supplement with protein bars, protein shakes, protein everything. The average adult with a “normal” BMI (18.5-24.9 BMI) who is moderately active requires approximately 0.8 grams (g) of protein per kilogram (kg) of body weight. This amount may vary with different metabolic disorders or conditions. It may be higher in those who are more active. If you are a highly active adult within a “normal” BMI you may require up to 1.2 g per kg of body weight. You can find your weight in kg by dividing your weight in pounds by 2.2. You can then multiply this by your “protein factor” (0.8, 1.2, etc). For example, as a moderately active adult with a normal BMI I require 0.8 g of protein for every 61.3 kg of body weight, so my protein needs come in at about 49 g of protein daily. 

Of course there are exceptions to every rule, so if you have a condition or are under some other metabolic stress your protein needs could very well be altered, so again consult your PCP or RD to gain clarity on what regimen is right for you.

Protein is also best digested and utilized when it is spread throughout the day. Attempting to meet your entire daily intake of protein in one sitting reduces your body’s ability to capitalize on breaking it all down and metabolizing it all adequately. Extra protein is not used efficiently by the body and may impose a metabolic burden on the bones, kidneys, and liver [1]. Protein is a nitrogen containing compound, nitrogen has an acidic pH and has to be secreted in the urine and so chronic overconsumption can create a metabolic demand on the body to extract calcium from the bones to act as a buffer and excrete more fluids from the body in the form of urine during the process of nitrogen excretion. According to a Literature Review published in the National Library of Medicine “Diet which is high in protein generates a large amount of acid in body fluids [1]. The kidneys respond to this dietary acid challenge with net acid excretion, and, concurrently, the skeleton supplies buffer by active resorption of bone resulting in excessive calcium loss. Moreover, acid loading directly inhibits renal calcium reabsorption leading to hypercalciuria in combination with the exorbitant bone loss”.

Your body only has a need for and can only metabolize so much protein as new tissue or enzymes or hormones or however your body needs protein, so the excess protein you consume is converted into glucose through a process called ”gluconeogenesis”.  

If there was anything I didn’t address that you still have questions about please feel free to leave a comment or send me a message and I will be happy to set the record straight if I can. If you enjoyed this post please give my page a follow to keep getting solid evidenced based info on how you can live your healthiest, plant-based life. 



Disclaimer: This post should not replace the advice of your doctor or Dietitian who is familiar with your individual medical history. Please consult your PCP or set up an appointment with a Registered Dietitian with any questions or concerns regarding the implementation of any drastic dietary changes

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