Testing must improve to detect supplement contamination

By Shane Starling

- Last updated on GMT

Related tags: Melamine

The United States Pharmacopeia (USP) is calling for more stringent testing methods and definitions to combat the growing problem of economically motivated adulteration (EMA) of dietary supplements.

The third party tester and standards setter recommended some actions to tackle a problem the Washington DC-based Council for Responsible Nutrition (CRN) said recently was “serious and growing concern”.

“Scientific solutions to better protect the public health by preventing the adulteration of protein-based food ingredients exist but will require further analytical work to validate methods for individual matrices,”​ said USP.

Highlighting protein and nitrogen determination, USP suggested three measures:

  • The need to move beyond total nitrogen-based and basic-IR methods for food protein measurement to protect the food supply from potentially harmful adulteration.
  • Develop matrix-specific definitions, methods, and reference materials for food protein measurement.
  • Screening methods to detect the presence of foreign substances by deviations from the unique and characteristic “signature” signal of an unadulterated sample should be developed to complement measurement techniques.

USP noted that food proteins were particularly prone to adulteration because they are so commonly used in the food chain. Nitrogen is typically used to determine the level of proteins in foods and dietary supplements.

USP said a classic and high-profile case was melamine contamination where Chinese milk suppliers had used melamine to mimic milk proteins.

Protein measurement it typically carried out using two nitrogen determination methods: Kjeldahl or Dumas.

“These techniques are now known to be vulnerable to adulteration with potentially devastating public health consequences because they lack selectivity/specificity for non-protein nitrogen and/or non-authentic protein,”​ USP said.

The firm said updates to the Kjeldahl method had the potential to detect non-protein nitrogen.

Other protein-specific methods such as Bradford could be used for aromatic amino acids, as well as infrared spectroscopy, the use of HPLC, immunoassays including multiplexed biosensors and microarrays, and mass spectrometry.


CRN’s vice president of scientific and regulatory affairs, Dr Andrew Shao, recently wrote to the FDA about EMA. In an eight-page submission he noted:

“Inadequate ingredient supplier qualification, especially among the smaller and less experienced dietary supplement manufacturers, coupled with the fact that ingredient suppliers are not subject to the dietary supplement GMPs, can be a contributor to sustaining a climate of EMA,”

Delivering EMA information to the FDA was questioned by Dr Shao, especially as it was not certain how the information would be used and publicized by the agency, with potentially devastating commercial results.

CRN suggested an anonymous web-based system would gather more, if less detailed, information, “and perhaps even erroneous leads” ​but it could be useful in identifying areas of concern.

Related topics: GMPs, QA & QC, Suppliers

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