What Food Labels Don’t Tell You About Protein Quality

When food labels report “protein,” they’re actually showing the total nitrogen content of a food multiplied by a conversion factor (usually 6.25).

 

That’s because nitrogen is unique to protein, so by measuring it, scientists can estimate how much protein is being ingested.

 

Here’s the catch: this doesn’t measure quality. 

 

It treats 10 grams of collagen, which lacks key amino acids like tryptophan, the same as 10 grams of whey isolate, which is packed with all nine essential amino acids.

 

This was behind a major controversy in the early 2000s known as protein spiking.  This is the practice of adding cheap nitrogen-containing compounds, like free-form amino acids (glycine, taurine, arginine, creatine, and even urea in some really shady products to boost their nitrogen levels.

 

This gave the deception that a product contains more protein than it really does, even though it lacks the essential amino acid profile that your body most critically needs.

 

This led to multiple class-action lawsuits against major supplement companies, and since then, the industry has largely cleaned up its act, but the practice hasn’t vanished completely.

 

At this point, I’m not accusing any brands of doing this, but I can see it becoming an issue in an arms race to pack more protein into a tasty snack.

 

There is another difference between proteins in how well they’re digested.
Originally, nutrition scientists used the PDCAAS (Protein Digestibility-Corrected Amino Acid Score) as a rating system that indicates how much of the protein your body can absorb, digest, and utilize as amino acids.

 

Here are some reasons why protein absorption is inhibited:

 

 

Plants contain compounds that bind to proteins or digestive enzymes, which reduce absorption. Common anti-nutrients include phytates (found in nuts, seeds, and grains), tannins (present in beans, legumes, and tea), and trypsin inhibitors (found in soy and legumes), which all reduce the amount of protein that’s absorbed.

 

 

Fiber is great for our health, but it also speeds up transit time, resulting in less time in the digestive zone. Additionally, it can physically trap proteins within plant cell walls.  For example, beans and lentils contain a good amount of protein, but also have a significant amount of fiber, which can lower their absorption.

 

 

Some proteins are simply harder to break down.  For example, a protein like gelatin has a tightly wound structure, while many plant proteins have complex structures that require more processing.  Whey and casein, in contrast, are easily disassembled; therefore, they have very high digestibility.

 

 

Heat, drying, and extrusion (like in cereals/protein snacks) can denature protein in good ways or bad.  Light processing (e.g., whey isolate microfiltration) preserves amino acids and increases digestibility.  Whereas harsh processing, such as high-heat treatment in bakery products, can damage amino acids and reduce digestibility.  Therefore, a 10g protein cereal or cookie may not deliver the same benefits as a single scoop of whey.

 

PDCAAS caps all scores at 1.0.  Meaning even if a protein is better than another (like whey vs. soy), they both get a “perfect” score.  This led to the development of a newer scoring method called DIAAS (Digestible Indispensable Amino Acid Score), which rates protein quality on a scale that extends beyond perfection.

 

• Milk / Whey: 130–140
• Egg: 100–115
• Beef: 100–125
• Chicken: 105–120
• Soy: 90–100
• Pea: 70–85
• Wheat/oat plant blends: 25–60

If you’ve gotten anything at all to this point, it’s that all grams of protein aren’t created equal. And while the nutrition label tells you how much, it does not tell you how good it is. 

 

If you’re in a bind to feed yourself, then by all means, grab something from a convenience store. If anything, the protein craze has made better options than a Snickers bar more accessible. 

 

But we should still strive to get our nutrition from whole foods.  It’s more satisfying, tends to provide more bang for the buck, and delivers many more nutrients on top of the amino acids our body needs.

 

Also, a “protein” version of French toast or Pop-Tarts doesn’t necessarily make it a high-quality food. You might get a few extra grams per serving, but it’s likely low quality, and you’re still eating the same stuff that made it a less-than-stellar nutrition option to begin with.

 

And if you want something tasty, then it should be worth it.  

 

Scrap the protein cookie and grab a real one, and enjoy the indulgence even more.