Amino Acid Spiking — The Supplement Industry's Protein Fraud Problem

Some protein powders aren’t what they claim. Here’s how the trick works.

“Amino acid spiking” (also called “nitrogen spiking”) is a practice where supplement manufacturers add cheap, non-protein amino acids — typically glycine, taurine, or creatine — to a protein powder to inflate the protein content on the label.

The trick exploits how protein content is measured. The standard Kjeldahl method doesn’t actually measure protein directly — it measures total nitrogen content and multiplies by 6.25 (the average nitrogen-to-protein conversion factor). Since glycine, taurine, and creatine all contain nitrogen, adding them inflates the nitrogen reading and therefore the apparent protein content. The product tests as “30g protein per serving” even though a significant portion of that nitrogen comes from cheap amino acids that don’t contribute meaningfully to muscle protein synthesis.

Glycine is particularly favored for spiking because it’s one of the cheapest amino acids available (it’s a byproduct of other manufacturing processes) and it contains 18.7% nitrogen by weight — higher than many intact proteins. Taurine is similarly cheap and nitrogen-rich.

How to spot it

Look at the ingredient panel. If you see glycine, taurine, or creatine listed as individual ingredients in a protein powder (not as part of the protein blend), and the product has a surprisingly high protein-per-serving claim relative to its price point, amino acid spiking may be occurring. Proprietary blends that don’t disclose individual amounts are a red flag.

The FDA requires that protein content claims on supplement labels reflect actual protein, not just nitrogen. But enforcement is limited under DSHEA, and independent testing labs have repeatedly found discrepancies between label claims and actual protein content in commercial products.

Why this matters for your amino acid supplement

This is one reason ingredient transparency matters. A product that lists each amino acid and its amount — rather than hiding behind proprietary blends — lets you verify exactly what you’re getting. OptimalAmino lists each amino acid and its exact amount on the Supplement Facts panel — no proprietary blends, no hidden ratios. Every batch is tested by five independently named labs (NSF International, Eurofins, Certified Laboratories, Twin Arbor Analytical, and UC Davis), and labels are registered on the NIH Dietary Supplement Label Database for public verification.

References

1. U.S. Food and Drug Administration. Dietary Supplement Labeling Guide. FDA
2. U.S. Government Accountability Office. Dietary supplements: FDA should take further actions to improve oversight and consumer understanding. GAO-09-250. 2009. GAO