New Protein Factors Cut Calculated Content by Up to 20%
A new European database of food-specific protein conversion factors lowers calculated protein content by 5% to 20% compared to the long-standing standard
A new scientific database has published food-specific factors that recalculate the protein content of thousands of foods, showing reductions of between 5% and 20% compared to the standard method. The NiCE Factors Database, developed by Germany's Max Rubner Institute (MRI) with European partners, covers 4,532 foods and is freely available online.
Protein in food is typically not measured directly. Instead, laboratories measure nitrogen content and multiply it by a standard factor of 6.25 to estimate protein. This factor, introduced nearly 200 years ago, assumes all protein contains 16% nitrogen. According to the MRI researchers, this figure is still mandated for food labelling under EU law and used in nutrient databases and dietary surveys. They argue it ignores differences between proteins and the nitrogen that comes from non-protein compounds, frequently leading to overstatements.
Revised Values Across Food Groups
The research team compiled data from 111 published studies to create new, more precise conversion factors for different food categories. Where direct measurements were lacking, they used averages from related foods.
The new factors significantly lower calculated protein values for many common foods. Meat from mammals and birds drops by around 15%, and whole eggs by about 13%. Milk and dairy products have the highest new factor at 5.86, meaning cow's milk protein is calculated as 5% to 7% lower than before.
| Food Group | New Protein Factor | Approximate Reduction vs. 6.25 |
|---|---|---|
| Legumes, Nuts, Oilseeds, Spices | 5.25 | ~16% |
| Fish and Seafood | 5.28 | ~16% |
| Meat and Meat Products | 5.41 | ~13-15% |
| Milk and Dairy Products | 5.86 | ~6-7% |
The lowest factors apply to low-protein foods like vegetables and starchy roots, where a larger share of nitrogen comes from non-protein sources. Among cereals, wheat bran and wheat germ show the largest reductions, between 15% and 21%.
Implications for Plant-Based Foods
The authors connect their work to the rising use of novel protein sources like legumes, algae, and insects, which have different compositions from conventional animal proteins. They also note that processed plant-based meat and dairy alternatives need their own reliable factors. Techniques like fermentation, extrusion, and heat treatment can change how much nitrogen is recovered in lab analysis. For now, EU labelling rules still require the 6.25 factor, so declared protein values on product packaging remain unchanged.
The paper discloses that one co-author has received funding from the Dutch Dairy Association and fees from the European Milk Forum. Data coverage in the database is currently uneven, with eggs, cereals, and milk far better studied than fruits or root vegetables.
The researchers plan ongoing updates, a Europe-wide call for new data, and a dedicated web interface. They state the database is, in their words, "ready to become the new standard reference for more accurate protein estimates."
