Testing of resveratrol, vitamin K2 products sold online reveals rampant quality deficiencies

Product testing in two ingredient categories, resveratrol and vitamin K2, has revealed serious quality problems among products sold online. The testing was done by supplement brand NOW and ingredient supplier Balchem, respectively. 

NOW released the results today of tests it had done for resveratrol supplements sold on Amazon.  

Resveratrol is a polyphenol found in many plant sources, including red grapes and Japanese knotweed (which is the most common source of extracted resveratrol sold in dietary supplements). 

NOW has sold a standalone resveratrol supplement since 2005. 

Majority of resveratrol products fail in potency and/or label transparency 

In this latest round of testing, the Bloomingdale, Ill.-based company bought two bottles each of 30 resveratrol supplements sold by lesser-known brands on Amazon. One bottle of each was tested at NOW’s facility and the other bottle was sent to Alkemist Labs in Garden Grove, Calif. for additional verification.   

Alkemist has participated in other rounds of the NOW testing program, which began in 2017. 

NOW tested the resveratrol content of the products and assessed the transparency and accuracy of their labels. The results, reminiscent of the other 17 rounds of such testing NOW has done over the program, revealed that very few of these brands met label claim. 

The testing revealed that 21 of the 30 products (one of which was NOW's own resveratrol SKU) failed to meet label claim. Six of the nine products had 100% or more of the claimed amount, while the other two had 89% and 97% and one test was inconclusive. A few of the failing products had about 50% of the labeled quantity, another one had 31% and the rest had 10% or less of the amount of resveratrol stated on the label.  

In addition, NOW found that most of the labels were misleading in one way or another. One repeat offender in NOW’s testing program — a company called aSquared Nutrition — listed 1000 milligrams (mg) of resveratrol for a two-capsule serving on the front label but then qualified that with the caveat “8% potency yield.” The company has failed every round of NOW’s testing in which its products have appeared. 

“‘Buyer beware’ certainly applies to resveratrol, as we found significant problems with most products tested,” said Dan Richard, NOW Health Group VP of Global Sales and Marketing. “Once again, NOW will share this info with Amazon directly and with the FDA, in hopes of further action.” 

Dismal results in vitamin K2 testing 

Ingredient supplier Balchem also announced testing results today, for 38 vitamin K2 products purchased on “one of the biggest e-commerce platforms in the United States.” Balchem, based in Montvale, N.J., supplies its own proprietary K2 ingredient branded as K2VITAL. 

Meeting label claim for vitamin K2 is not only a matter of how much of the vitamin is in the bottle, but also the form that it is in, according to the company. The menaquinone-7 (abbreviated as MK7) form of vitamin K2 can be present in two isomers, designated as cis and trans. The trans isomer form is far more bioavailable that the cis form, according to Balchem. 

Balchem sent the 38 products to Alkemist Labs for testing. The testing revealed that only 29% of the 38 products met label claim for both overall content and the presence of the trans-MK7. 

The company noted that vitamin K2 is tricky to formulate with, and products in which the vitamin is not properly protected might see their potency diminish rapidly on the shelf when combined with other ingredients, such as some minerals. 

“This journey towards transparency started in 2018, when we tested for assay and purity of vitamin K2 products in Germany, and the results were shocking,” said Dominik Mattern, VP of science, business development and marketing for Balchem. 

Mattern said because of those test results and advocacy on the part of Balchem, products in the German market now feature an “all-trans” mark to better inform consumers. 

“We aim to increase awareness about the unique specifications of vitamin K2, emphasizing the necessity for the correct isomer, known as all-trans MK-7, as well as the importance of microencapsulation and proper protection in the presence of specific compounds such as minerals,” Mattern added. 

Amazon and aSquared did not respond to requests for comment in time for publication.