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

NOW and Balchem have released the test results of their online-sold products. They respectively tested resveratrol and vitamin K2 products. The results showed that only a very small number of products met the label claims in all aspects. The product tests conducted in the two ingredient categories of resveratrol and vitamin K2 revealed serious quality issues with online-sold products. The tests were carried out by supplement brand NOW and ingredient supplier Balchem respectively. NOW announced today the results of its tests on 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.   

Since its launch in 2017, the NOW testing program has conducted 17 rounds, and Alkemist has also participated in several of these rounds. NOW tested the resveratrol content of these products and evaluated the transparency and accuracy of their labels. The test results were consistent with those of the previous 17 rounds of testing in this project, indicating that very few of these brands' products met the claims on their labels. The test found that among 30 products, 21 (including NOW's own resveratrol products) did not reach the claimed content on the labels. Among the 9 products, 6 had content that reached or exceeded the claimed amount by 100%, and the other two were 89% and 97% respectively. One test result was undetermined. Among the products that did not meet the standards, several had content approximately 50% of the claimed amount, one was 31%, and the content of the remaining products was 10% or less of the claimed amount

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 

The ingredient supplier, Balker Company, also released the relevant test results today. These tests covered 38 vitamin K2 products purchased from "the largest e-commerce platform in the United States". Balker Company, located in Montvale, New Jersey, named its own brand of K2 ingredients as K2VITAL.

The company stated that meeting the label claims for vitamin K2 not only depends on the vitamin content in the bottle, but also on its form. Balker Company said that the menaquinone-7 (abbreviated as MK7) form of vitamin K2 can have two isomers, which are called cis and trans. The bioavailability of the trans isomer is much higher than that of the cis isomer.

Balker Company sent these 38 products to Alkenist Laboratory for testing. The test results showed that only 29% of these 38 products met the overall content claimed on the label and the presence of trans MK7.

The company pointed out that the formula of vitamin K2 is rather complex. If the vitamins in the product are not properly protected, when mixed with other components (such as certain minerals), their efficacy may rapidly decline on the shelves.

“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.