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Understanding the science behind protein bioavailability


Protein is a macronutrient. It is made up of amino acids, also known as the building blocks of proteins. But we don’t just eat protein and that’s it. How well proteins are used by the body depends on their bioavailability. Here, we’ll explore what protein bioavailability means, what affects it, and the best sources available.

What is protein bioavailability?

Protein is an essential component of a healthy diet. It’s made up of chemical building blocks which are essential for building and repairing your muscles, and for making hormones and enzymes. Proteins are also an important energy source, influencing your metabolism.

But not all proteins are created equal. The quality of proteins is determined by several factors, such as: 

  • Amino acid composition 

  • Digestibility 

  • Bioavailability of amino acids1 

Protein bioavailability is important because it indicates how well the protein can be used by the body. For example, a protein that has a high bioavailability means it is easily absorbed when it’s eaten.

But that doesn’t mean you should always pick the most bioavailable sources. A critical part of a balanced diet is eating a combination of foods to achieve a varied amino acid intake.

Plus, varying your food choices also means you’ll be consuming a wide range of different foods and nutrients. But we’ll talk about that a bit more later on. 

Factors affecting protein bioavailability?

There are several protein bioavailability factors to consider. They include:

  • Digestibility: Digestibility is how well the protein can be broken down by your digestive enzymes into peptides and amino acids. Proteins that have higher bioavailability ratings are easily digested. However, digestion can also be affected by factors such as cooking and processing methods.

  • Amino acid profile: Amino acids are the basic building blocks of proteins. The human body can produce some amino acids but not all of them. Those that it can’t produce (there are nine in total), must be obtained through your diet, and are called essential amino acids. Because these come from food, it’s important to understand their different profiles:

    • Complete proteins: These are foods that contain all nine essential amino acids and are considered the highest-quality proteins. They are most often found in animal-based sources such as chicken, meat, and eggs.

    • Incomplete proteins are foods that contain some amino acids and are usually found in plant-based foods, like legumes. 

    • Complementary protein sources. These are a mix of incomplete proteins that when eaten together provide your body with all nine amino acids.

  • Cooking methods: Protein bioavailability can be affected by the way you cook your food. A study conducted in 2021 found that cooking legume pastes made from soybeans, lentils, or peas improved their digestibility and even their antioxidant activity.2 However, keep in mind that overcooking or high heat can affect the quality of proteins. 

How much protein should I eat?

Most adults need around 0.75g of protein per kilo of body weight each day. On average, this equates to about 55g for men and 45g for women. However, your requirements may vary based on your fitness journey.

For example: 

  • If you are looking to lose weight, you’ll likely need to increase your protein intake. Research shows that high protein diets containing between 1.2 and 1.6g of protein per kilo of body weight each day improve appetite, weight management, and heart health.5 Protein is preferable for weight loss because it suppresses hunger hormones, making you feel fuller for longer, and even boosts metabolism.

Protein is vital for building, maintaining, and repairing tissue, including muscle. So, anyone who is looking to build muscle mass will naturally need to increase their protein intake. To encourage muscle growth, you’ll generally need between 1.2 and 2.2g of proteins per kilogram of body weight per day.

Notable protein sources

Now that you know how much protein you need, let’s look at some of the best sources.

Animal-based proteins

Animal proteins often contain all nine essential amino acids. Here are our top 5 animal-based protein sources.

Whey protein 

Whey protein is the natural protein isolated from the liquid part of cow’s milk, called whey. Whey protein isolate has high bioavailability, so is absorbed well by the body. It’s often a preferred source for athletes who want to gain muscle but lose fat because it has high protein utilization rates.


Eggs, particularly the whites, are an excellent source of protein that’s easy to absorb. Although the egg white is almost pure protein, it’s important to eat the whole egg as the yolk is packed with other important nutrients. One egg can provide around 6 to 8g of protein.


Fish is highly nutritious and a great source of protein. It also provides Omega-3 fatty acids, a type of healthy fat that’s good for your heart and brain. Consuming fish and shellfish is perfect if you follow a pescetarian diet. You could try:

  • Crab (20.5g per 100g) 

  • Salmon (20.4g per 100g) 

  • Sardines (19.8g per 100g) 

  • Prawns (shrimp) (17.6g per 100g) 

  • Cod (17.5g per 100g) 

  • Pollack (17.4g per 100g)3 

Probably one of the most popular and common protein choices, chicken breast is packed with approximately 27g of protein per 100g. It’s also an excellent source of B vitamins and low in fat.

The protein bioavailability of red meat is a bit lower than the other sources, but it’s often a preferred choice for anyone who is looking to satisfy their hunger cravings. Plus, red meat is an excellent source of iron which is essential for healthy red blood cells and high energy levels. 

Plant-based proteins

It’s important to eat a wide variety of food, and there are plenty of plant-based sources of protein available. Try adding some of these to your diet, even if you eat meat and fish. If you’re vegan or vegetarian, these foods are perfect for boosting your amino acid intake.


Almonds are a great source of plant protein. Each 35g serving is packed with approximately 7g of both essential and non-essential amino acids. These nuts are also nutrient-dense and good sources of healthy fats.


If you follow a plant-based diet, getting enough protein can be a challenge, but with 9g in every 100g, lentils are a must. They’re also high in fiber and low in fat. Lentils can be boiled and eaten on their own or as an ingredient in soups, stews, and even homemade veggie burgers.


Another tasty wholegrain that’s perfect for vegan or vegetarian diets is quinoa. One cup of quinoa provides around 8g of protein. And, it’s a complete protein because it contains all nine essential amino acids. It’s also naturally gluten-free.

Peanut butter

Another high-quality nutritious source of protein is peanut butter. This popular snack is perfect for everyone (unless you have a nut allergy) and can be a great addition to many snacks and meals. It also packs a pretty big protein punch too, with around 25g per 100g.


Soybean-based foods like edamame, tofu, and tempeh are popular in East Asian cuisine. They are an excellent source of protein because they contain all the essential amino acids your body needs. Because they are so versatile, these foods can be added to most dishes.

Let’s recap:

Protein is a macronutrient essential for a healthy diet. Protein bioavailability describes how well a protein can be utilized by the body. Some foods have a higher bioavailability than others, but it’s important to eat a wide range of foods to promote balance. Variety will also help you to consume all nine essential amino acids. 

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  1. Hoffman, J. R., & Falvo, M. J. (2004). Protein - Which is Best? Journal of sports science & medicine, 3(3), 118–130. 

  2. Gallego, M., Arnal, M., Barat, J. M., & Talens, P. (2020). Effect of Cooking on Protein Digestion and Antioxidant Activity of Different Legume Pastes. Foods (Basel, Switzerland), 10(1), 47. 

  3. (2019) High protein seafood: What fish has the most protein? Available at: (Accessed: 31 May 2023).  

  4. (No date) Almonds. Available at: