The Shocking Whey Protein Myth: Why the ‘18% Usable’ Claim Is Flat-Out Wrong

In recent years, one particular whey protein myth has spread across the internet: the claim that whey protein is “only 18% usable by the body,” meaning 82% is supposedly wasted. Sounds alarming, right? This misleading statement, often repeated by online gurus and promoters of the Master Amino Acid Pattern (MAP) supplement, has caused understandable confusion among athletes and fitness enthusiasts.

Let’s set the record straight: this claim is scientifically false, misleading, and based on a nonstandard, self-serving method of measurement that has no standing in modern nutrition science.

Where the 18% Whey Protein Myth Comes From

The number originates from a 1992 paper by Mauro Lucà-Moretti, who conducted studies on “Net Nitrogen Utilization” (NNU) while developing and promoting his product, Master Amino Acid Pattern (MAP®).

In those studies, Lucà-Moretti compared the nitrogen balance of subjects consuming different protein sources — egg, whey, soy, and his own amino acid blend (SON/MAP). He concluded that most proteins had very low “utilization” rates (as low as 16–18%) and that his proprietary amino acid formula had a “99% utilization rate.”

However, Lucà-Moretti’s methodology did not measure protein digestion or absorption. Instead, it was based on a nonstandard calculation of nitrogen retention, which heavily favored the precise amino acid ratios found in his own supplement. The result conveniently “proved” that MAP was superior to all dietary proteins.

In other words, the “18%” number was more of a marketing gimmick than a metabolic truth acknowledged by the scientific community.

What Modern Science Actually Says About Whey Protein

To understand how misleading that 18% claim is, you need to look at how protein quality is actually measured in legitimate nutrition science. Two standardized systems are used worldwide:

1. PDCAAS (Protein Digestibility Corrected Amino Acid Score)
2. DIAAS (Digestible Indispensable Amino Acid Score)

Here’s how whey protein stacks up:

As you can see, whey scores at the top of both scales, with real absorption rates exceeding 95–98%, not 18%. These numbers mean that whey protein is virtually completely digested and provides all essential amino acids in ideal ratios for human metabolism.

In other words, whey protein is among the most efficiently used and bioavailable proteins known — not 18% usable, but closer to 95–98% absorbed and fully utilized by the body.

The Real Science on Whey Digestion and Absorption

Peer-reviewed research consistently demonstrates whey’s superior bioavailability:

• Boirie et al. (1997) found that whey protein is a “fast” protein, rapidly digested and absorbed, leading to a sharp rise in plasma amino acids and robust muscle protein synthesis (MPS).
• Reidy & Rasmussen (2016) reviewed dozens of studies and concluded that whey is among the most anabolic protein sources available, primarily due to its high leucine content and rapid absorption rate.
• Tang et al. (2009) showed that whey produced significantly greater MPS compared to soy or casein, even when matched for total protein intake.

These findings utterly contradict the idea of the whey protein myth that 82% of it is “wasted.”

Why the NNU Method Is Misleading

Lucà-Moretti’s “Net Nitrogen Utilization” calculation is not recognized by any major scientific body. It’s a non-standard, proprietary metric designed to highlight the supposed superiority of free-form amino acid mixtures, such as MAP.

Here’s why it doesn’t hold up:

• It doesn’t measure actual digestion or absorption.
  NNU measures the amount of nitrogen retained, but this can be influenced by factors such as timing, amino acid ratios, and metabolic conditions, in addition to protein quality.
• It favors amino acid blends.
  Free-form amino acids require no digestion, so they appear to “perform better” in nitrogen balance tests, even though real foods and whole proteins provide more sustained amino acid availability.
• It’s not peer-validated or reproducible.
  Independent studies rarely use or even cite Lucà-Moretti’s NNU method because it lacks methodological transparency and scientific rigor.

The “18%” number, therefore, represents a cherry-picked artifact of this unrecognized system. It is not a reflection of real protein metabolism.

What About MAP’s Own Score?

If MAP were evaluated using accepted methods like PDCAAS or DIAAS, it would score roughly the same as whey: around 1.0–1.1. Because free-form essential amino acids are completely digestible, their PDCAAS can’t exceed 1.0 (the cap), and their DIAAS would hover around 100–110, depending on formulation.

In other words, MAP doesn’t outperform whey at all when measured by objective standards. It only looks superior under its own self-invented metric.

The Bottom Line

Let’s summarize the facts:

• The “18% usable” claim for whey protein is based on a non-standard, proprietary metric (NNU), rather than actual digestion or utilization data.
• Whey protein is one of the most digestible, bioavailable, and anabolic proteins in existence, with over 95% absorption and a PDCAAS of 1.0.
• The DIAAS score for whey typically exceeds 1.1, confirming its superior amino acid profile and usability.
• The NNU/MAP data were primarily used as a marketing tactic, rather than as peer-accepted science.

When you use credible metrics, whey protein doesn’t just hold its ground, it sets the gold standard for protein quality.

So, the next time someone claims that “whey protein is only 18% usable,” remember: that number is marketing spin, not science.

References

• Boirie, Y., et al. (1997). Slow and fast dietary proteins differently modulate postprandial protein accretion. American Journal of Clinical Nutrition, 77(4), 868–876.
• Tang, J.E., et al. (2009). Differential stimulation of myofibrillar protein synthesis with whey, soy, and casein ingestion in elderly men. Journal of Applied Physiology, 107(3), 987–992.
• Reidy, P.T., & Rasmussen, B.B. (2016). Role of ingested amino acids and protein in the promotion of resistance exercise–induced muscle protein anabolism. Journal of Nutrition, 146(2), 155–183.
• FAO (2013). Dietary protein quality evaluation in human nutrition: Report of an FAO Expert Consultation. Food and Agriculture Organization of the United Nations.
• Lucà-Moretti, M. (1992). Comparative study of subjects’ Net Nitrogen Utilization (NNU) while receiving SON, a nutritional amino acid formula, or high biological value egg protein, or egg protein amino acid formula. JIMHA, 1:33–42.