Some protein powders on the market deliver significantly less protein than the amount advertised on their labels. Why the discrepancy? These powders contain non-protein ingredients that can skew the results of the standard method used to measure protein content, making it appear a product offers more protein than it actually does.
This missing protein exposes a big problem: some food manufacturers—whether accidentally or intentionally—are misinterpreting the standard method for measuring protein in products such as protein powders. Due to the industry’s low barriers to entry and countless manufacturers revolving in and out, it’s urgent to call out this faulty practice and clarify the proper way protein should be measured and reported.
Most food manufacturers calculate protein using the Kjeldahl test, which measures a product’s nitrogen content. Because protein contains nitrogen, the level of nitrogen can be used to estimate a product’s protein amount. This analysis is approved by the Association of Analytical Communities and accepted by FDA.
But there’s a widely known limitation of this method: if the product contains nitrogen-rich ingredients that aren’t proteins, the nitrogen level will be increased—and as a result, the amount of protein will seem to be higher, even though it isn’t. That’s why any non-protein nitrogen sources must be accounted for and subtracted from the total amount of nitrogen, as determined by the Kjeldahl analysis.
Examples of non-protein, nitrogen-rich ingredients in some protein products include creatine, taurine and non-essential amino acids, such as glycine and alanine. Some of these sources have especially high nitrogen levels for their weight, which can only exacerbate the problem. These ingredients are typically much less expensive than a high-quality protein ingredient like whey.
FDA doesn’t stipulate how manufacturers account for the non-protein, nitrogen-rich ingredients when reporting a product’s protein content. However, consumers deserve to have labels and promotional materials accurately reflect a product’s actual nutritional content. Bypassing the important step of subtracting out nitrogen from non-protein, nitrogen-rich ingredients artificially inflates protein measurements and is misleading.
This ongoing issue recently prompted both the Council for Responsible Nutrition (CRN) and the American Herbal Products Association (AHPA) to set new policies for how member companies should calculate the amount of protein in their products.
Doing the Math
When using the Kjeldahl test to calculate protein, you need to account for, and subtract, non-protein nitrogen before finalizing a product’s true protein content. It’s a standard good manufacturing practice.
Here’s how: multiply the grams of the added nitrogen-containing ingredient by a “back-calculation factor” based on an ingredient’s percent of nitrogen by weight, and then subtract it from the Kjeldahl test results. For example, a product that includes 5 grams of creatine monohydrate and 2 grams of glycine per serving would have 11.1 grams of apparent protein from these ingredients that need to be subtracted from the Kjeldahl test results (based on [5 x factor 1.761 for creatine] + [2 x factor 1.166 for glycine] = 11.1).
Reputable manufacturers account for non-protein nitrogen ingredients and don’t mislead consumers with overstated protein promises. But not all do, especially those who make high protein claims using inexpensive ingredients that can act as fillers instead of quality protein.
The Kjeldahl method remains an effective way to measure protein content, but all manufacturers must calculate protein totals the correct way and be transparent about the true amount of protein in their products. Consumers expect—and rightfully so—truth in labeling.
Jenna A. Bell has a PhD in Health and Human Performance with an emphasis on Exercise Science. She is a registered dietitian and has completed two Ironman competitions, three marathons and several sprint and Olympic distance triathlons and road races. She is the chair of the Sports Cardiovascular and Wellness Nutrition Dietetic Practice Group and a member of the EAS Academy Advisory Panel.