Biological Value: Why Not All Protein Is Created Equal

In 2013, 5.6 billion US dollars were spent worldwide on protein-based supplements. But now, faced with the huge range of high-protein foods, it’s easy to lose sight of which protein is actually right for you. And unfortunately, we have to tell you: not all protein is created equal.

To shed some light on the topic, this article explains what biological value means when it comes to proteins, and how you can use it as a benchmark for high-quality protein. We’ll also break down the term “PDCAAS” and explain the role your digestion plays.

Why Proteins Are Important for Us

We can’t survive without protein. This essential nutrient should be on your plate every day. Athletes and fitness enthusiasts already know this, but for most people, protein often only plays a minor role.

Proteins are made up of chains of building blocks called amino acids. There are 20 of them in total, and they can be combined in all sorts of ways. The result is proteins with a huge range of functions in our bodies. Here are some interesting examples of what they do:

• Contractile proteins: The protein myosin makes your muscles contract so you can flex and move.
• Transport proteins: Hemoglobin is an iron-containing protein complex that transports oxygen through your bloodstream.
• Structural proteins: These include elastin and collagen. They act as a framework for tissues and cells. Both give ligaments and tendons their flexibility and help you perform at your best during sports.

To make these vital proteins, your body needs amino acids. Some of these building blocks can be produced by your body itself. Leucine, tryptophan, threonine, methionine, valine, isoleucine, and phenylalanine, on the other hand, are called essential because your body can’t make them on its own. 

That’s why you need to get them from your diet every day. The German Nutrition Society recommends consuming 0.8 grams of protein per kilogram of body weight daily. If you work out intensely and want to build muscle, you should even increase your intake to 1.5 grams of protein per kilogram.

What’s often overlooked is the amino acid profile of the proteins we eat. If you always eat the same protein source, you might not be covering your full amino acid needs.

The Biological Value of Proteins

The amino acid composition of a protein largely determines how valuable it is for your body: Does it contain only certain amino acids, or a broad spectrum? The more completely a dietary protein can be converted into your body’s own proteins, the more important it is for you.

The quality of proteins is defined by their biological value – Orgainic.

“The amino acid composition of a protein largely determines how valuable it is for your body.”

To determine the quality of a food, egg protein is used as a reference. Its biological value is set at 100 percent. If the test protein has a more complex amino acid profile and can be used even better than its competitor to build your body’s own proteins, its value is above 100. If not, it’s below 100. 

The biological value of protein isn’t a mandatory part of food labeling. That’s why we’ve put together a table for you with a selection of biological values for different proteins.

Table 1: Biological value of selected foods

Value Is Calculated in the Lab

The biological value of a food is determined in the lab and requires a bit of chemistry know-how. 

Amino acids contain a nitrogen atom in their amino group. When proteins are digested, the nitrogen forms compounds with other substances. A good example is urea nitrogen, which is excreted when you go to the bathroom. Lab technicians can use complex measurement methods to identify this compound and draw conclusions about protein digestion. 

The determination of the biological value of a food takes place in three steps:

• Step 1: A test animal is fed the test food over a longer period of time.
• Step 2: Measurement of the remaining nitrogen amount in the body from protein consumption. For this, the nitrogen content in the animal's urine (UN) and feces (FN) is determined.
• Step 3: The measured values are inserted into the following formula:

Biological Value = Nitrogen content in food (IN) minus UN minus FN divided by IN minus FN

The Maximum of Biological Value – Choosing the Right Foods

Mother Nature hasn’t just given us two or three protein-rich foods, but has packed almost all foods with different proteins. This means we can combine foods to optimally supply our bodies with amino acids. We don’t have to stick to the bodybuilder protein “whole egg.”

The smart combination of foods increases their biological value – Orgainic. 

“We can combine foods to optimally supply our bodies with amino acids.”

If your meal consists of 65 percent potatoes and 35 percent whole egg, the amino acid profiles complement each other and the value of your meal rises to 136. The same goes for corn and beans. On their own, each achieves a value of 72. But if you combine 52 percent beans with 48 percent corn, you break the 100 mark.

If you’re now super motivated to find the best food partners for your favorite dish, we have to slow you down a bit. The right combination is tested in the lab, and with a bit of luck you’ll find a suitable study.

Didn’t find what you were looking for? If you’re good at math, you can calculate the so-called Essential Amino Acid Index (EAA Index) by looking at the amino acid content in your food. Scientist Bernard L. Oser developed this formula to estimate biological value.

Criticism of the Measurement Method

Protein value only describes the amount of protein our body retains after eating. However, studies are mostly conducted on rats, so the relation to humans is missing. Still, because of their similar digestive mechanism, these animals provide a good basis for new insights.

Furthermore, we don’t focus our diet on just one food, but combine them. This affects the digestibility of our food and thus protein utilization.

The best example for athletes is post-workout nutrition: If we add four parts carbohydrates to the protein, we not only replenish our depleted energy stores, but also promote digestion and the absorption of amino acids into the worked muscles through insulin release, making us feel immediately rebuilt.

The More Modern Metric: PDCAAS

A better measure for the quality and usability of proteins is the “Protein Digestibility Corrected Amino Acid Score” (PDCAAS). This value takes into account not only the amino acid index but also the digestibility of proteins.

The score of a food is on a scale from 0.0 to 1.0, with the latter indicating high protein quality. If the value is 0.5, about 50 percent of the amino acids are used for the body’s own proteins. The rest can, for example, be used directly for energy production.

Below you’ll find valuable amino acid sources that are easily digestible and support your body in building proteins. You should include foods with a high score in your daily meals to ensure you’re getting enough amino acids. After all, strong muscles need solid building blocks.

Table 2: PDCAAS of selected foods

This is how PDCAAS is calculated:

Smarter food combinations for high-quality protein

Proteins are important, but smartly combining foods ensures a complete amino acid spectrum. This nutrient is made up of amino acids that our bodies use to build their own proteins. They have numerous functions that keep us performing at our best.

The importance of foods for our bodies is described by biological value and PDCAAS. While protein value only describes the percentage of amino acids absorbed by our bodies, the PDCAAS also analyzes the amino acid profile and the digestibility of foods. The latter is therefore used more often to describe protein quality.

Both measures are important to consume complete protein and cover a broad amino acid spectrum. After all, strong muscles need plenty of building blocks to grow.

Reading tip: Want to upgrade your food choices and eat better? Check out our blog post “Organic Supplements – The Sustainable Guide for Your Nutrition” to find the right products for you.

Title image by Malidate Van. More images from Pixabay.