Protein Bioavailability: Why It Matters and What You Need to Know

Protein Bioavailability: Why It Matters and What You Need to Know

Protein Bioavailability: Why It Matters and What You Need to Know

Along with carbohydrates and fats, protein is one of three macronutrients our bodies need in large quantities. Among other things, protein is essential for maintaining healthy muscles, bones, and skin, managing blood pressure, aiding digestion, boosting immunity, and producing hormones, enzymes, and hemoglobin (a protein found in red blood cells that helps carry oxygen around the body).

Although we can get protein from whole food sources (food that hasn’t been processed) and protein supplements, the efficacy of how we use that protein depends on protein bioavailability.

For our bodies to function at their best, we need to understand what protein bioavailability is, why it matters, and which food sources provide us with the highest-quality protein.

Amino Acids: The Building Blocks of Protein

Before we delve into protein bioavailability, let’s explore one of the most important elements of protein: amino acids. These are the basic building blocks of protein. Our bodies can produce some amino acids but not all of them. Those we can’t create are known as essential amino acids, and they need to come from our diet or from protein supplements.

The nine essential amino acids are:

  • Leucine
  • Isoleucine
  • Valine
  • Tryptophan
  • Lysine
  • Methionine
  • Histidine
  • Phenylalanine
  • Threonine

The first three on the list above — leucine, isoleucine, and valine — are branched-chain amino acids (BCAAs), so named because of the branched side chain in their molecular structure. Branched-chain amino acids are especially important for athletes as they are heavily involved in:

  • Muscle synthesis, which is the process of building and repairing muscle
  • Boosting energy
  • Enhancing performance
  • Increasing endurance
  • Improving recovery
  • Counteracting cortisol, which is a stress hormone
  • Regulating blood sugar levels

How Does Your Body Use Protein?

Digestion pf protein diagram

Before dietary protein can be absorbed, it must be reduced to its essential amino acids. This digestion process starts in the stomach, where the peptide bonds holding the protein together are broken down. A percentage of the resulting amino acids is absorbed through the small intestine and moved into the bloodstream to be transported to where they are needed. These amino acids are recombined through protein synthesis into other proteins so your body can use them — for example, to build or repair muscle. 

However, some proteins break down and are absorbed more easily than others.

Protein bioavailability indicates how well the protein from a specific food source can be used by the body. 

A protein with high bioavailability is easily absorbed after digestion and the body can then use a high percentage of the amino acids. For example, while soy is generally a good source of protein, an egg is more bioavailable — far more of the protein in it is available for use by the body.

How Do You Measure Protein Quality?

The protein quality of a food source is usually rated on two criteria: amino acid profile and bioavailability. 

Amino Acid Profile

Since we must get all our essential amino acids from food, it’s crucial to understand the amino acid compositions of different types of protein sources. 

  • Complete protein sources contain all essential amino acids. These are the highest-quality proteins and are mostly animal products like meat, chicken, fish, eggs, and dairy. However, a diet high in animal protein can raise a variety of health concerns and in these cases, supplements in the form of protein powder can be useful.
  • Incomplete protein sources are usually plant-based. They are “incomplete” since they don’t contain all the essential amino acids. For example, beans are deficient in methionine and rice lacks lysine.
  • Complementary protein sources are a combination of incomplete proteins, which together provide all the essential amino acids. For example, when beans are combined with brown rice, or peanut butter with bread, they become a complete protein source.


As we’ve discussed, bioavailability reflects how easily the body can use a specific protein.

Once a protein is digested and broken down into its component amino acids, a certain proportion of those amino acids are effectively absorbed through the small intestine and moved into the bloodstream. Bioavailability can then be tested by measuring the presence of amino acids in the bloodstream.

By refining sources like whey or pea protein, the bioavailability of that protein can be improved to a lesser or greater extent, depending on the technology involved. For example, studies done comparing Ingredient Optimized products with standard products show significantly increased bioavailability in the Ingredient Optimized products.

Protein Quality Rating Methods

There are different protein rating methods, each with its limitations. Still, they’re useful standards to measure nutritional value.

One commonly used rating is the protein digestibility-corrected amino acid score (PDCAAS). This takes into account both the amino acid composition of a protein and how well it can be digested. It measures food sources against a reference value of 1, which is the score for an egg. Whey protein also rates very highly on the PDCAAS scale.

Although it has served its purpose relatively well for many years, there have been a number of shortcomings identified in the PDCAAS method. These include discrepancies resulting from the age of the subject, the effect of antinutritional factors, and where in the digestive tract the amino acid content is measured. PDCAAS is also capped at a maximum score of 100. Therefore proteins with a raw score that exceed 100 are not effectively represented in the final numbers.

A slightly newer rating method is the Digestible Indispensable Amino Acid Score (DIAAS), recommended by the Food and Agriculture Organization of the United Nations (FAO). While this addresses some of the shortcomings of the PDCAAS and is considered more accurate, it also has limitations, particularly around its application to plant-based foods.

Why Does Protein Bioavailability Matter?

Human nutrition is complex and for optimum health, we must consume different protein sources. The only way to make sure you’re taking in enough high-quality protein is to eat plenty of the appropriate whole foods. 

Processed foods such as frozen dinners, bacon, deli meats, and packaged snacks don’t count! Many essential nutrients are destroyed during processing, and the final products are often very high in sugar, salt, unhealthy trans fats, and artificial ingredients intended to enhance taste and texture, and extend shelf life. 

The recommended Dietary Reference Intake of protein is 0.8 grams per kg of body weight each day. On average, men need at least 56 grams of protein per day while women need at least 46 grams.

Your dietary protein intake should primarily come from a variety of whole foods to ensure that you consume other important nutrients. Protein should also come from sources with high bioavailability so that your body can use most of the protein they provide.

Animal-Based Sources With High Protein Bioavailability

Some animal proteins have high protein bioavailability

If you’re comfortable with animal-based products, these are excellent complete protein options you can add to your diet:

  • Grass-fed red meat, especially beef, is high in amino acids and healthy fats, as well as a variety of other important nutrients like iron, vitamin B12, and zinc.
  • Poultry, such as chicken and turkey, preferably free-range, is low in carbohydrates and fats.
  • Wild-caught seafood, particularly oily fish like salmon, tuna, and mackerel. Wild fish have more natural and varied diets and are free of the antibiotics routinely given to farmed fish.
  • Game, such as venison and pheasant, is lower in fat and naturally grass-fed.
  • Whole eggs can give you up to 6 grams of digestible protein from one medium egg, but if you’re concerned about cholesterol, egg whites work well too.
  • Dairy, including butter and cheese, are good sources for those who can tolerate lactose. Cottage cheese is especially high in slow-digesting casein protein, providing longer-term effects such as sustained muscle growth and repair overnight, when eaten before bedtime.
  • Whey, a dairy-derived protein beloved by athletes and bodybuilders, is one of the highest-quality proteins. It contains plenty of BCAAs, especially leucine, which helps to build and repair muscle tissue, plus other vitamins and minerals. It’s low in carbohydrates and fat, while being highly bioavailable, digesting fast and quickly boosting blood flow to muscles. It’s often taken as a supplement, which usually comes in one of three forms: whey protein powder, whey protein concentrate, or whey protein isolate, which is the purest.

Plant-Based Sources With High Protein Bioavailability

Array of plant-based proteins

You can also get protein from plant sources, although they usually have lower protein bioavailability. It’s also a good idea to combine them with a complementary food source to ensure you’re getting all the essential amino acids. Try these plant proteins:

  • Quinoa is high in vegetable protein plus other important nutrients like iron, vitamin B6, and magnesium.
  • Soy-based products, such as tempeh and soybeans, are high in protein, vitamins, and minerals. Because they are fairly neutral in taste, they can take on any flavoring.
  • Nuts, especially walnuts and almonds (rather than peanuts), can be consumed as-is or in the form of nut butter. Paired with grains, such as rice or bread, nut butters can create a complete protein. 
  • Legumes, for example, soy beans or chickpeas, are excellent sources when eaten with complementary foods like brown rice.

Do You Need to Take a Protein Supplement? 

ioWhey Protein and ioWhey Pea Protein have high protein bioavailability

Protein is critical for proper functioning of the body, so it’s no wonder that many people use protein supplements to improve sports performance, help with weight management, or recover from an illness or surgery. 

Protein supplements are also a great alternative to bypass some of the potential issues that can stem from protein sources. For example, animal products often raise health concerns about saturated fat and cholesterol, which are traditionally associated with cardiovascular disease. 

While vegetable proteins do not present these same risks, they are not complete sources of protein on their own. Supplements, on the other hand, can provide all the essential amino acids without the aforementioned risks. That said, not all protein supplements are created equal.

High-quality supplements like those supplied by Ingredient Optimized (io) are ideal as they are specially formulated for high protein bioavailability. The clinically tested, patent-pending Ingredient Optimized technology ensures you get optimal nutrition and the physical results you want. 

In fact, ioWhey protein has 123% increased bioavailability compared to standard whey proteins. Plus, it comes in a neutral-tasting formula that’s easy to incorporate into food, beverages, and supplements.

Optimize Your Health With High-Quality Protein

The truth is, not all protein is the same. The amino acid profile and protein bioavailability of any food source you consume will determine how much nutrition you actually derive from it. To optimize your health, make sure you understand which sources give you the best return on your nutritional investment. Also, consider including high-quality supplements — such as the dairy-based ioWhey Protein or plant-based ioPea Protein — in your daily meal planning. It could change your life.