Protein Bioavailability

Did you know that protein bioavailability is an important factor to consider when designing an optimal nutrition plan? The ability of the body to absorb and use the amino acids found in protein sources affects how efficiently we can access the essential nutrients that our bodies need.

Protein is an essential macronutrient that is necessary for the structure and function of the human body. Without adequate protein intake, our bodies would lack the energy and material needed to repair muscle tissue and cells, build new tissues, and break down food into energy. 

Every week I meet with clients (mostly women), that are lacking in energy. When we look at their food journal, it becomes clear that they are not getting anywhere near the amount of protein their body needs, especially considering that many are in the perinatal phase (before, during and after preganacy).

So let’s dig in. Because along with fat, carbohydrates and water, protein is one of our macronutrients (nutrients we need a lot of).

What is protein bioavailibity?

Before we get to digging into protein bioavailbility (how much of our protein we can absorb), let’s first understand what is protein and how we get it.

Proteins are made from sequences of amino acids that need to be broken down into smaller pieces to create enzymes, hormones, neurotransmitters and other essential elements of our body. Amino acids are the building blocks for the body’s cells, organs, tissues, and muscles. We require proteins to form the backbone of our bodies and facilitate the necessary biochemical processes it needs to function.

It may surprise you to know, but proteins are essential for hormone production, especially those that are related to the digestive system. They play a role in oxygen transport, immune system cells, enzyme and antibody creation, and the production of neurotransmitters. 

In order to ensure your body receives the right amount of protein, it is important to understand the different sources of protein, how much protein you need, and the various ways that protein can be assessed. 

Good Sources of Protein

There are many options for good sources of protein. In addition to protein, many animal-based food sources contain essential vitamins and minerals. Some of the best sources of meat-based protein include beef, chicken, pork, turkey, salmon, tuna, and eggs. 

Here are some examples of protein amounts, per 100 grams (appx 3.5 oz)- this would be approximately the size of the palm of your hand:

**All numbers from My Food Data calculator

  • Chicken breast- 32 grams
  • Flank steak- 28 grams
  • Turkey breast- 30 grams
  • Pork loin- 27 grams
  • Salmon- 27 grams
  • Shrimp- 23 grams

Here are a few more options in the egg and dairy category:

  • Egg – 11 grams (2 medium eggs)
  • Cheddar Cheese- 24 grams (1 oz= 6.8 grams)
  • Gouda, Manchego cheese- 25 grams (1 oz= 7.1 grams)
  • Cottage cheese- 11 grams (about half a cup)
  • Quark cheese- 10 grams (about half a cup)
  • Yogurt- 3 grams avg. (about half a cup)
  • Whole Milk- 3.2 grams (a full cup would have 8 grams)

As you can see, you can get a decent amount of protein from a small portion of animal based products.

Good Sources of Plant-Based Protein

Plant-based proteins can also be good sources of protein, and many are also loaded with vitamins, minerals, and fiber. Some of the best sources of plant-based protein include legumes, nuts, and seeds. 

For the sake of comparison, all values are for 100 grams, and I made a note of how much volume more or less it would look like.

  • Lentils- 9 grams (half a cup)
  • Black beans, Pinto beans- 9 grams (just over half a cup)
  • Navy beans- 8.2 grams (just over half a cup)
  • Split peas- 8.3 grams (just over half a cup)
  • Garbanzo beans (Chickpeas)- 4.6 grams (a bit under half a cup)
  • Natto (fermented soy beans)- 19 grams (just over half a cup)
  • Quinoa- 4.4 grams (just over half a cup)
  • White rice, Brown rice- 2.7 grams (half a cup)
  • Bread- 8-11 grams (one slice of bread= 3 grams)

And let’s look at some nuts and seeds:

  • Prepared tahini- 6.7 grams (a 2 Tbsp portion= 2 grams)
  • Almond butter- 19 grams (a 2 Tbsp portion= 6 grams)
  • Peanut butter- 22 grams ( a 2 Tbsp portion= 7 grams)
  • Chia seeds- 17 grams (1 Tbsp= 1.7 grams)
  • Flax seeds- 18 grams (1 Tbsp ground = 1.3 grams)
  • Almonds- 21 grams (1 oz portion, which is ~28 almonds= 6 grams)
  • Walnuts- 15 grams (1 oz portion, which is ~14 halves= 4.3 grams)
  • Pistachios- 20 grams (1 oz portion, which is ~49 kernals= 5.7 grams)

Not all Protein is Created Equal

Let me nerd out for a second, because whenever we talk about nutrients we need to consider bioavailibility– meaning can our bodies USE the nutrients in the food.

Our bodies use 22 amino acids that combine to form proteins. Of these, nine are considered essential, meaning that the body cannot produce them. These nine are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.

The remaining 13 amino acids can be created by the body, although this can be difficult in some cases. The conditionally essential amino acids are arginine, cysteine, glutamine, glycine, proline, and tyrosine, and ideally you should get them from food.

The final amino acids are easily made from other amino acids: alanine, aspartic acid, asparagine, glutamic acid, serine, selenocysteine and pyrrolysine, fall into this category.

Limiting Amino Acid

Why should you care? Beacuse not all food sources of protein, have all of the essential amino acids that we need. When evaluating dietary protein intake, also called protein quality evaluation, researchers look at what’s called the limiting amino acids (the amino acids which are missing in a certain dietary protein).

As a general rule, certain protein sources, that are mostly animal based have a complete amino acid profile, meaning they are “complete proteins”. Most plant based proteins are incomplete proteins (with the exception of soy, quinoa and buckwheat). Furthermore, getting all of the amino acids out of our foods requires good digestion.

To try to account for this variablity, professional organizations and researchers have tried to come up with calculation to help compare various sources of protein according to their amino acid content. Here are two of the most commonly cited.

Protein Digestibility Corrected Amino Acid Score

The Protein Digestibility Corrected Amino Acid Score (PDCAAS) is the most commonly used method for assessing the nutritional quality of protein. This scoring system was developed by the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) and assigns a score of 0-1 to a food based on its protein content and the bioavailability of its amino acid composition. The higher the score, the higher the quality of that food’s protein. 

Here are a few examples of the PDCAAS Scores:

  • Egg – 1.0
  • Milk – 1.0
  • Chicken breast – 1.0
  • Lentils – 0.52-0.71
  • Chickpeas – 0.52
  • Almonds- 0.35

Digestible Indispensable Amino Acid Score

The Digestible Indispensable Amino Acid Score (DIAAS) is a newer method of assessing protein quality. This system was propsed by the Food and Agriculture Organization of the United Nations and takes into account all nine essential amino acids and their digestibility, using a score of 0-1, but a food can be scored over 1 as well. This score is meant to be a better measure of protein quality than the PDCAAS and is more accurate, as it takes into account the digestibility of the food. 

Here are the same foods and their scores on the DIAAS:

  • Egg-  1.13
  • Milk – 1.14
  • Chicken breast – 1.08 
  • Lentils –  0.54
  • Chickpeas – 0.67
  • Almonds- 0.40

Rather than make controversial statements, you can draw your own conclusions on which protein sources to consume based on the numbers. So now that we’ve talked about WHAT protein to eat, let’s chat about how much you need!

A Note on Protein Powders

You may have noticed that I didn’t include any protein powders in the various lists above. Whey protein from milk, whey protein isolate, soy protein powder, and vegetable protein (like pea protein) powder are all very high in protein. However, they can be less accessible to some people. There may be cases where consuming a protein powder is indicated, but you would want to talk about that with a health care professional.

Calculating Your Protein Needs

To ensure your body is receiving the right amount of protein, it is important to calculate how much you need to eat in a day.

You may have heard of the “RDA” which stands for Recommended Dietary Allowance. It is an estimated amount of the various vitamins, minerals, and other nutrients an average, healthy person should consume each day. The RDA is based on research in nutrition and is created by the Food and Nutrition Board of the Institute of Medicine of the National Academy of Sciences.

RDA is calculated from a variety of factors, including age, sex, lifestyle, diet, and health status. The values are usually listed as a range, with the lower bound being the amount needed to meet the needs of the majority of healthy individuals, and the upper bound being the amount needed to meet the needs of those at the highest risk of deficiency.

The Recommended Dietary Allowance for Protein

Currently, the RDA for protein is 0.8 grams of protein per kilogram of body weight per day. This can be calculated by multiplying your weight in kilograms by 0.8. For example, if you weigh 70 kilograms, your protein needs would be 56 grams of protein per day.*

However, new research is showing that for many populations, this may not be sufficient. Individuals with certain health conditions or dietary needs might require higher or lower amounts of certain nutrients.

There are many ways to fulfill the daily RDA for protein. It is recommended to consume a variety of protein sources such as fish, eggs, poultry, meat, nuts, and legumes. For those who do not eat meat, consuming a variety of plant-based sources of protein is important to balance out their amino acid ratios. Supplementing with protein powder can also be beneficial for those who struggle to reach their daily protein needs. 

Who needs more protein?*

There are several factors that influence how much protein you need, such as age, activity level, and health status. Children, for example, need more protein than adults since their bodies are still growing and developing. Here are some categories of people that need a higher protein intake.


The American Dietetic Association (ADA) recommends that children aged 4 to 13 years consume 1.0 to 1.5 grams of protein per kilogram of body weight per day. Adolescents aged 14 to 18 years can consume 1.2 to 1.7 grams of protein per kilogram each day. 

Active individuals

Athletes and active individuals typically need more protein than the average person since exercise increases their daily protein needs. The ADA recommends that athletes and active individuals consume 1.2 to 2.0 grams of protein per kilogram of body weight per day. 

Pregnant and Lactating Women

Pregnant and lactating women also need more protein than the average person. The ADA recommends that pregnant women consume 1.1 grams of protein per kilogram of body weight, while lactating women should consume 1.3 grams per kilogram of body weight. 

Chronic health conditions

Finally, people with certain autoimmune diseases or the majority of conditions under the GAPS umbrella, need more protein than the average person. People with autoimmune diseases should consult their healthcare provider and figure out an ideal nutrition plan.

Now that you know the factors that influence your protein needs, you can begin to determine the right amount of protein for you. The best way to do this is to consult with a nutritional therapy practitioner. They can help you calculate your exact protein needs based on your age, activity level, and health status. 

The Bottom line

Protein is an essential macronutrient that is necessary for the structure and function of the body. It is important to understand the different sources of protein, how to assess the quality of protein, and how to calculate your protein needs. By eating a variety of protein sources and consuming the right amount of protein per day, you can give your body the building blocks it needs for optimal health and performance.

The importance of proteins to our bodies cannot be underestimated. They are responsible for building and maintaining tissues, organs, nerves and muscles, regulating metabolism, transporting oxygen, and forming antibodies to protect us from infection. Without proteins, we wouldn’t be able to survive. By understanding their role, we can better equip ourselves to live a healthy life and maintain optimum health.

Eating a balanced diet that contains sufficient proteins can make all the difference. If you’re ready to get some personalized support with your nutrition, book a discovery call and let’s chat!

* Everyone. The answer is everyone. The guideline were calculated with the “average” sedentary adult in mind. If you want your health to be better than “average”, bump yourself into that “active individuals” category!


American Dietetic Association: “Position of the American Dietetic Association: Nutrition for Physical Fitness and Athletic Performance.” November 2009.

Institute of Medicine (U.S.). (2005). Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients) (Vol. 1). Washington (D.C.): National Academies Press (U.S.).

Mathai, J. K., Liu, Y., & Stein, H. H. (2017). Values for digestible indispensable amino acid scores (DIAAS) for some dairy and plant proteins may better describe protein quality than values calculated using the concept for protein digestibility-corrected amino acid scores (PDCAAS). The British journal of nutrition, 117(4), 490–499.

Phillips S. M. (2017). Current Concepts and Unresolved Questions in Dietary Protein Requirements and Supplements in Adults. Frontiers in nutrition, 4, 13.

Sá, Amanda & Hang, Jiayi & Jardine, Laura & Bett, Kirstin & House, James. (2023). How different amino acid scoring patterns recommended by FAO/WHO can affect the nutritional quality and protein claims of lentils. Sustainable Food Proteins. 10.1002/sfp2.1008.

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